M. Pantaleo [Editor] 
Internet Draft                                      
Document: draft-ietf-megaco-h248v2-00.txt          Ericsson 
Expires: May 2002                                  November 2001 
 
 
                           Draft Megaco/H.248v2 
 
 
Status of this Memo 
 
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Abstract 
    
   This document contains the new draft text for recommendation H.248 
   v2.  The document refelects changes, clarifications and corrections 
   defined in the approved H.248 Implementors' Guide, Document TD 15 
   (Plen), Porto Seguro, 28 May “ 8 June 2001. Some more changes, 
   clarifications and corrections are added as defined in the new H.248 
   Implementors' Guide draft, Document TD-28, Dublin 29 October “ 2 
   November 2001. Furthermore it contains the following new 
   functionalities: 
    
   ¹    auditing single properties, events, signals and statistics 
   (Document AVD-2068) 
   ¹    indicating that capabilities have changed in the Media Gateway 
   (Document APC-1911) 
   ¹    playing a signal on the Root Termination (Document APC-2002) 
   ¹    extendable context properties (Document D129, Porto Seguro, 28 
   May “ 8 June 2001) 
   ¹    handling of multiple transaction pending (Document D93, Porto 
   Seguro, 28 May “ 8 June 2001) 
   ¹    topology enhancement (Document TD-42, Dublin, 29 October “ 2 
   November 2001) 
   ¹    profile handling (Document AVD-2122, Dublin, 29 October “ 2 
   November 2001) 
     
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   ¹    auditing context properties (Document AVD-2120, Dublin, 29 
   October “ 2 November 2001)  
 
 
Table of Contents 
    
   Abstract..........................................................1 
   Summary...........................................................7 
   1.      SCOPE.....................................................7 
    
   2.     REFERENCES.................................................7 
   2.1    Normative references.......................................7 
   2.2    Informative references.....................................9 
    
   3.     DEFINITIONS...............................................10 
    
   4.     ABBREVIATIONS.............................................11 
    
   5.     CONVENTIONS...............................................12 
    
   6.     CONNECTION MODEL..........................................12 
   6.1    Contexts..................................................15 
   6.1.1  Context Attributes and Descriptors........................15 
   6.1.2  Creating, Deleting and Modifying Contexts.................16 
   6.2    Terminations..............................................16 
   6.2.1  Termination Dynamics......................................17 
   6.2.2  TerminationIDs............................................17 
   6.2.3  Packages..................................................18 
   6.2.4  Termination Properties and Descriptors....................18 
   6.2.5  Root Termination..........................................20 
    
   7.     COMMANDS..................................................21 
   7.1    Descriptors...............................................22 
   7.1.1  Specifying Parameters.....................................22 
   7.1.2  Modem Descriptor..........................................23 
   7.1.3  Multiplex Descriptor......................................23 
   7.1.4  Media Descriptor..........................................23 
   7.1.5  Termination State Descriptor..............................24 
   7.1.6  Stream Descriptor.........................................24 
   7.1.7  LocalControl Descriptor...................................25 
   7.1.8  Local and Remote Descriptors..............................26 
   7.1.9  Events Descriptor.........................................29 
   7.1.10 EventBuffer Descriptor....................................31 
   7.1.11 Signals Descriptor........................................31 
   7.1.12 Audit Descriptor..........................................33 
   7.1.13 ServiceChange Descriptor..................................34 
   7.1.14 DigitMap Descriptor.......................................34 
   7.1.15 Statistics Descriptor.....................................39 
   7.1.16 Packages Descriptor.......................................39 
   7.1.17 ObservedEvents Descriptor.................................39 
   7.1.18  Topology Descriptor......................................39 
   7.1.19 Context Attribute Descriptor..............................42 
   7.1.20 Error Descriptor..........................................43 
   7.2    Command Application Programming Interface.................43 
     
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   7.2.1  Add.......................................................43 
   7.2.2  Modify....................................................45 
   7.2.3  Subtract..................................................45 
   7.2.4  Move......................................................47 
   7.2.5  AuditValue................................................48 
   7.2.6  AuditCapabilities.........................................50 
   7.2.7  Notify....................................................52 
   7.2.8  ServiceChange.............................................52 
   7.2.9  Manipulating and Auditing Context Attributes..............56 
   7.2.10  Generic Command Syntax...................................58 
   7.3    Command Error Codes.......................................58 
    
   8.     TRANSACTIONS..............................................58 
   8.1    Common Parameters.........................................60 
   8.1.1  Transaction Identifiers...................................60 
   8.1.2  Context Identifiers.......................................60 
   8.2    Transaction Application Programming Interface.............61 
   8.2.1  TransactionRequest........................................61 
   8.2.2  TransactionReply..........................................61 
   8.2.3  TransactionPending........................................63 
   8.3    Messages..................................................64 
    
   9.     TRANSPORT.................................................64 
   9.1    Ordering of Commands......................................66 
   9.2    Protection against Restart Avalanche......................67 
    
   10.    SECURITY CONSIDERATIONS...................................67 
   10.1   Protection of Protocol Connections........................67 
   10.2   Interim AH scheme.........................................68 
   10.3   Protection of Media Connections...........................68 
    
   11.     MG-MGC CONTROL INTERFACE.................................69 
   11.1   Multiple Virtual MGs......................................69 
   11.2   Cold Start................................................70 
   11.3   Negotiation of Protocol Version...........................71 
   11.4   Failure of an MG..........................................71 
   11.5   Failure of an MGC.........................................72 
    
   12.    PACKAGE DEFINITION........................................73 
   12.1   Guidelines for defining packages..........................73 
   12.1.1 Package...................................................74 
   12.1.2 Properties................................................74 
   12.1.3 Events....................................................76 
   12.1.4 Signals...................................................76 
   12.1.5 Statistics................................................76 
   12.1.6 Procedures................................................77 
   12.2   Guidelines to defining  Properties, Statistics and Parameters 
   to Events and Signals............................................77 
   12.3   Lists.....................................................77 
   12.4   Identifiers...............................................78 
   12.5   Package Registration......................................78 
    
   13.    PROFILE DEFINITION........................................78 
    
     
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   14.     IANA CONSIDERATIONS......................................79 
   14.1   Packages..................................................79 
   14.2   Error Codes...............................................80 
   14.3   ServiceChange Reasons.....................................80 
   14.4   Profiles..................................................81 
    
   ANNEX A BINARY ENCODING OF THE PROTOCOL (NORMATIVE)..............82 
   A.1    Coding of wildcards.......................................82 
   A.2    ASN.1 syntax specification................................83 
   A.3    Digit maps and path names................................102 
    
   ANNEX B TEXT ENCODING OF THE PROTOCOL (NORMATIVE)...............104 
   B.1    Coding of wildcards......................................104 
   B.2    ABNF specification.......................................104 
   B.3    Hexadecimal octet coding.................................118 
   B.4    Hexadecimal octet sequence...............................119 
    
   ANNEX C TAGS FOR MEDIA STREAM PROPERTIES (NORMATIVE)............120 
   C.1    General Media Attributes.................................120 
   C.2    Mux Properties...........................................122 
   C.3    General bearer properties................................122 
   C.4    General ATM properties...................................122 
   C.5    Frame Relay..............................................125 
   C.6    IP.......................................................125 
   C.7    ATM AAL2.................................................125 
   C.8    ATM AAL1.................................................127 
   C.9    Bearer Capabilities......................................128 
   C.10   AAL5 Properties..........................................136 
   C.11   SDP Equivalents..........................................136 
   C.12   H.245....................................................137 
    
   ANNEX D TRANSPORT OVER IP (NORMATIVE)...........................139 
   D.1    Transport over IP/UDP using Application Level Framing....139 
   D.1.1  Providing At-Most-Once Functionality.....................139 
   D.1.2  Transaction identifiers and three-way handshake..........140 
   D.1.3  Computing retransmission timers..........................140 
   D.1.4  Provisional responses....................................141 
   D.1.5  Repeating Requests, Responses and Acknowledgements.......142 
    
   D.2     Using TCP...............................................143 
   D.2.1  Providing the At-Most-Once functionality.................143 
   D.2.2  Transaction identifiers and three way handshake..........144 
   D.2.3  Computing retransmission timers..........................144 
   D.2.4  Provisional responses....................................144 
   D.2.5  Ordering of commands.....................................144 
    
    
   ANNEX E BASIC PACKAGES (NORMATIVE)..............................145 
   E.1    Generic..................................................145 
   E.1.1  Properties...............................................145 
   E.1.2  Events...................................................145 
   E.1.3  Signals..................................................146 
   E.1.4  Statistics...............................................147 
    
     
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   E.2    Base Root Package........................................147 
   E.2.1  Properties...............................................147 
   E.2.2  Events...................................................149 
   E.2.3  Signals..................................................149 
   E.2.4  Statistics...............................................149 
   E.2.5  Procedures...............................................149 
    
   E.3    Tone Generator Package...................................150 
   E.3.1  Properties...............................................150 
   E.3.2  Events...................................................150 
   E.3.3  Signals..................................................150 
   E.3.4  Statistics...............................................151 
   E.3.5  Procedures...............................................151 
    
   E.4    Tone Detection Package...................................151 
   E.4.1  Properties...............................................151 
   E.4.2  Events...................................................151 
   E.4.3  Signals..................................................153 
   E.4.4  Statistics...............................................153 
   E.4.5  Procedures...............................................153 
    
   E.5    Basic DTMF Generator Package.............................153 
   E.5.1  Properties...............................................153 
   E.5.2  Events...................................................153 
   E.5.3  Signals..................................................154 
   E.5.4  Statistics...............................................154 
   E.5.5  Procedures...............................................154 
    
   E.6    DTMF detection Package...................................155 
   E.6.1  Properties...............................................155 
   E.6.2  Events...................................................155 
   E.6.3  Signals..................................................156 
   E.6.4  Statistics...............................................156 
   E.6.5  Procedures...............................................156 
    
   E.7    Call Progress Tones Generator Package....................157 
   E.7.1  Properties...............................................157 
   E.7.2  Events...................................................157 
   E.7.3  Signals..................................................157 
   E.7.4  Statistics...............................................158 
   E.7.5  Procedures...............................................158 
    
   E.8    Call Progress Tones Detection Package....................158 
   E.8.1  Properties...............................................158 
   E.8.2  Events...................................................158 
   E.8.3  Signals..................................................158 
   E.8.4  Statistics...............................................158 
   E.8.5  Procedures...............................................158 
    
   E.9    Analog Line Supervision Package..........................159 
   E.9.1  Properties...............................................159 
   E.9.2  Events...................................................159 
   E.9.3  Signals..................................................161 
   E.9.4  Statistics...............................................162 
     
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   E.9.5  Procedures...............................................162 
   E.9.6  Error Code...............................................162 
    
   E.10   Basic Continuity Package.................................162 
   E.10.1 Properties...............................................162 
   E.10.2 Events...................................................162 
   E.10.3 Signals..................................................163 
   E.10.4 Statistics...............................................163 
   E.10.5 Procedures...............................................163 
    
   E.11   Network Package..........................................164 
   E.11.1 Properties...............................................164 
   E.11.2 Events...................................................165 
   E.11.3 Signals..................................................166 
   E.11.4 Statistics...............................................166 
   E.11.5 Procedures...............................................166 
    
   E.12   RTP  Package.............................................166 
   E.12.1 Properties...............................................167 
   E.12.2 Events...................................................167 
   E.12.3 Signals..................................................167 
   E.12.4 Statistics...............................................167 
   E.12.5 Procedures...............................................168 
    
   E.13   TDM Circuit  Package.....................................168 
   E.13.1 Properties...............................................168 
   E.13.2 Events...................................................169 
   E.13.3 Signals..................................................169 
   E.13.4 Statistics...............................................169 
   E.13.5 Procedures...............................................169 
    
   APPENDIX A EXAMPLE CALL FLOWS (INFORMATIVE).....................170 
   A.1    Residential Gateway to Residential Gateway Call..........170 
   A.1.1  Programming Residential GW Analog Line Terminations for Idle 
   Behavior........................................................170 
   A.1.2  Collecting Originator Digits and Initiating Termination..172 
   References......................................................180 
   Author's Address................................................180 
     
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Summary 
    
   [H.323-specific text omitted.] 
    
     
1.       SCOPE 
    
   Recommendation H.248 defines the protocols used between elements of 
   a physically decomposed multimedia gateway, used in accordance with 
   the architecture as specified in Recommendation H.323.  There are no 
   functional differences from a system view between a decomposed 
   gateway, with distributed sub-components potentially on more than 
   one physical device, and a monolithic gateway such as described in 
   H.246. This recommendation does not define how gateways, multipoint 
   control units or interactive voice response units (IVRs) work.  
   Instead it creates a general framework that is suitable for these 
   applications. 
     
   Packet network interfaces may include IP, ATM or possibly others.  
   The interfaces will support a variety of SCN signalling systems, 
   including tone signalling, ISDN, ISUP, QSIG, and GSM.  National 
   variants of these signalling systems will be supported where 
   applicable. 
     
    
2.      REFERENCES 
    
2.1     Normative references 
    
   ATM Forum (1994): "User-Network Interface, Version 4.0". 
    
   ITU-T Recommendation H.225.0: "Call Signalling Protocols and Media 
   Stream Packetization for Packet Based Multimedia Communications 
   Systems". 
    
   ITU-T Recommendation H.235: "Security and encryption for H-Series 
   (H.323 and other H.245-based) multimedia terminals". 
    
   ITU-T Recommendation H.245: "Control Protocol for Multimedia 
   Communication". 
    
   ITU-T Recommendation H.323: "Packet Based Multimedia Communication 
   Systems". 
    
   ITU-T Recommendation I.363.1, ŸB-ISDN ATM Adaptation Layer 
   specification: Type 1 AAL÷. 
    
   ITU-T Recommendation I.363.2, ŸB-ISDN ATM Adaptation Layer 
   specification: Type 2 AAL÷. 
    
   ITU-T Recommendation I.363.5, "B-ISDN ATM Adaptation Layer 
   specification: Type 5 AAL". 
    
     
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   ITU-T Recommendation I.366.1, ŸSegmentation and Reassembly Service 
   Specific Convergence Sublayer for the AAL type 2÷. 
    
   ITU-T Recommendation I.366.2, ŸAAL type 2 service specific 
   convergence sublayer for trunking÷. 
    
   ITU-T Recommendation I.371, ŸTraffic control and congestion control 
   in B-ISDN÷. 
    
   ITU-T Recommendation Q.763, ŸSignalling System No. 7 - ISDN user 
   part formats and codes÷. 
    
   ITU-T Recommendation Q.765.5, ŸApplication transport mechanism “ 
   Bearer independent call control (BICC)÷. 
    
   ITU-T Recommendation Q.931: "Digital Subscriber Signalling System 
   No.  1 (DSS 1) - ISDN User-Network Interface Layer 3 Specification 
   for Basic Call Control". 
    
   ITU-T Recommendation Q.2630.1, ŸAAL Type 2 Signalling Protocol 
   (Capability Set 1)÷. 
    
   ITU-T Recommendation Q.2931, ŸBroadband Integrated Services Digital 
   Network (B-ISDN) - Digital Subscriber Signalling System No. 2 (DSS 
   2) - User-Network Interface (UNI) - Layer 3 specification for basic 
   call/connection control÷. 
    
   ITU-T Recommendation Q.2941.1, ŸDigital Subscriber Signalling System 
   No. 2 “ Generic Identifier Transport÷. 
    
   ITU-T Recommendation Q.2961, ŸBroadband integrated services digital 
   network (B-ISDN) - Digital subscriber signalling system no.2 (DSS 2) 
   - additional traffic parameters÷. 
    
   ITU-T Recommendation Q.2961.2, ŸDigital subscriber signalling system 
   No. 2 - Additional traffic parameters: Support of ATM transfer 
   capability in the broadband bearer capability information element.÷ 
    
   ITU-T Recommendation Q.2965.1, "Digital subscriber signalling sytem 
   No. 2 “ Support of Quality of Service classes." 
    
   ITU-T Recommendation Q.2965.2,  "Digital subscriber signalling 
   system No. 2 “ Signalling of individual Quality of Service 
   parameters." 
    
   ITU-T Recommendation X.213, ŸInformation technology - Open System 
   Interconnection - Network service definition plus Amendment 1 
   (08/1997), Addition of the Internet protocol address format 
   identifier÷. 
    
   ITU-T Recommendation V.76, "Generic multiplexer using V.42 LAPM-
   based procedures". 
    
     
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   ITU-T Recommendation X.680 (1997): "Information technology-Abstract 
   Syntax Notation One (ASN.1): Specification of basic notation". 
    
   ITU-T Recommendation H.246 (1998), "Interworking of H-series 
   multimedia terminals with H-series multimedia terminals and 
   voice/voiceband terminals on GSTN and ISDN". 
    
   RFC 1006, "ISO Transport Service on top of the TCP, Version 3", 
   Marshall T. Rose, Dwight E. Cass, May 1987. 
    
   RFC 2234, "Augmented BNF for Syntax Specifications: ABNF", D. 
   Crocker, P. Overell, November 1997. 
    
   RFC 2327, "SDP: Session Description Protocol", M. Handley, V. 
   Jacobson, April 1998. 
    
   RFC 2402, "IP Authentication Header", S. Kent, R. Atkinson, November 
   1998. 
    
   RFC 2406, "IP Encapsulating Security Payload (ESP)", S. Kent, R. 
   Atkinson, November 1998. 
    
2.2     Informative references 
    
   ITU-T Recommendation E.180/Q.35 (1998): "Technical characteristics 
   of tones for the telephone service". 
    
   CCITT Recommendation G.711 (1988), ŸPulse Code Modulation (PCM) of 
   voice frequencies÷. 
    
   ITU-T Recommendation H.221 (05/99),÷Frame structure for a 64 to 1920 
   kbit/s channel in audiovisual teleservices÷. 
    
   ITU.T Recommendation H.223 (1996), ŸMultiplexing protocol for low 
   bit rate multimedia communication÷. 
    
   RFC 768, "User Datagram Protocol", J.Postel, August 1980. 
    
   RFC 791, "Internet protocol", J.Postel, September 1981. 
    
   RFC 793, "TRANSMISSION CONTROL PROTOCOL", J.Postel, September 1981. 
    
   RFC 1661, "The Point-to-Point Protocol", W. Simpson, July 1994. 
    
   RFC 1889, "RTP: A Transport Protocol for Real-Time Applications", H. 
   Schulzrinne, S. Casner, R. Frederick, V. Jacobson, January 1996. 
    
   RFC 1890, "RTP Profile for Audio and Video Conferences with Minimal 
   Control", H. Schulzrinne, January 1996. 
    
   RFC 2401, "Security Architecture for the Internet Protocol", S. 
   Kent, R. Atkinson, November 1998. 
    
     
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   RFC 2543, " SIP: Session Initiation Protocol", M. Handley, H. 
   Schulzrinne, E. Schooler, J. Rosenberg, March 1999. 
    
   RFC 2460, "Internet Protocol, Version 6 (IPv6) Specification", S. 
   Deering, R. Hinden, December 1998. 
    
   RFC 2805, "Media Gateway control protocol architecture and 
   requirements", N. Greene, M. Ramalho, B. Rosen, April 1999. 
    
   ITU-T Recommentation Q.724 (1998): ŸSignalling procedures÷. 
    
   ITU-T Recommendation Q.764 (1999): ŸSignalling system No. 7 “ ISDN 
   user part signalling procedures÷. 
    
   ITU-T Recommendation Q.1902.4 (2001) ŸBearer independent call 
   control protocol - Basic call procedures÷. 
    
    
3.      DEFINITIONS 
    
   Access Gateway: A type of gateway that provides a User to Network 
   Interface (UNI) such as ISDN.  
    
   Descriptor: A syntactic element of the protocol that groups related 
   properties.  For instance, the properties of a media flow on the MG 
   can be set by the MGC by including the appropriate descriptor in a 
   command. 
    
   Media Gateway (MG): The media gateway converts media provided in one 
   type of network to the format required in another type of network. 
   For example, a MG could terminate bearer channels from a switched 
   circuit network (e.g., DS0s) and media streams from a packet network 
   (e.g., RTP streams in an IP network).  This gateway may be capable 
   of processing audio, video and T.120 alone or in any combination, 
   and will be capable of full duplex media translations.  The MG may 
   also play audio/video messages and perform other IVR functions, or 
   may perform media conferencing. 
    
   Media Gateway Controller (MGC): Controls the parts of the call state 
   that pertain to connection control for media channels in a MG.    
    
   Multipoint Control Unit (MCU): An entity that controls the setup and 
   coordination of a multi-user conference that typically includes 
   processing of audio, video and data. 
    
   Residential Gateway: A gateway that interworks an analogue line to a 
   packet network. A residential gateway typically contains one or two 
   analogue lines and is located at the customer premises. 
    
   SCN FAS Signalling Gateway: This function contains the SCN 
   Signalling Interface that terminates SS7, ISDN or other signalling 
   links where the call control channel and bearer channels are 
   collocated in the same physical span.  
    
     
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   SCN NFAS Signalling Gateway: This function contains the SCN 
   Signalling Interface that terminates SS7 or other signalling links 
   where the call control channels are separated from bearer channels.  
    
   Stream: Bidirectional media or control flow received/sent by a media 
   gateway as part of a call or conference. 
    
   Trunk: A communication channel between two switching systems such as 
   a DS0 on a T1 or E1 line. 
    
   Trunking Gateway: A gateway between SCN network and packet network 
   that typically terminates a large number of digital circuits. 
    
    
4.      ABBREVIATIONS  
    
   This recommendation defines the following terms. 
    
   ALF          Application Layer Framing 
    
   ATM          Asynchronous Transfer Mode 
    
   CAS          Channel Associated Signalling 
    
   DTMF         Dual Tone Multi-Frequency 
    
   FAS          Facility Associated Signalling 
    
   GSM          Global System for Mobile communications 
    
   GW           GateWay 
    
   IANA         Internet Assigned Numbers Authority 
    
   IP           Internet Protocol 
    
   ISUP         ISDN User Part 
    
   IVR          Interactive Voice Response 
    
   MG           Media Gateway 
    
   MGC          Media Gateway Controller 
    
   NFAS         Non-Facility Associated Signalling 
    
   PRI          Primary Rate Interface 
    
   PSTN         Public Switched Telephone Network  
    
   QoS          Quality of Service 
    
   RTP          Real-time Transport Protocol 
    
     
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   SCN          Switched Circuit Network 
    
   SG           Signalling Gateway 
    
   SS7          Signalling System No. 7 
    
    
5.      CONVENTIONS 
    
   In this recommendation, "shall" refers to a mandatory requirement, 
   while "should" refers to a suggested but optional feature or 
   procedure. The term "may" refers to an optional course of action 
   without expressing a preference. 
    
     
6.      CONNECTION MODEL 
    
   The connection model for the protocol describes the logical 
   entities, or objects, within the Media Gateway that can be 
   controlled by the Media Gateway Controller.  The main abstractions 
   used in the connection model are Terminations and Contexts.   
    
   A Termination sources and/or sinks one or more streams.  In a 
   multimedia conference, a Termination can be multimedia and sources 
   or sinks multiple media streams.  The media stream parameters, as 
   well as modem, and bearer parameters are encapsulated within the 
   Termination.  
    
   A Context is an association between a collection of Terminations. 
   There is a special type of Context, the null Context, which contains 
   all Terminations that are not associated to any other Termination.  
   For instance, in a decomposed access gateway, all idle lines are 
   represented by Terminations in the null Context. 
    
   Following is a graphical depiction of these concepts.  The diagram 
   of Figure 1 gives several examples and is not meant to be an all-
   inclusive illustration.  The asterisk box in each of the Contexts 
   represents the logical association of Terminations implied by the 
   Context. 
    
      
     
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         +------------------------------------------------------+ 
         |Media Gateway                                         | 
         | +-------------------------------------------------+  | 
         | |Context                          +-------------+ |  | 
         | |                                 | Termination | |  | 
         | |                                 |-------------| |  | 
         | |  +-------------+             +->| SCN Bearer  |<---+-> 
         | |  | Termination |   +-----+   |  |   Channel   | |  | 
         | |  |-------------|   |     |---+  +-------------+ |  | 
       <-+--->| RTP Stream  |---|  *  |                      |  | 
         | |  |             |   |     |---+  +-------------+ |  | 
         | |  +-------------+   +-----+   |  | Termination | |  | 
         | |                              |  |-------------| |  | 
         | |                              +->| SCN Bearer  |<---+-> 
         | |                                 |   Channel   | |  | 
         | |                                 +-------------+ |  | 
         | +-------------------------------------------------+  | 
         |                                                      | 
         |                                                      | 
         |                    +------------------------------+  | 
         |                    |Context                       |  | 
         |  +-------------+   |              +-------------+ |  | 
         |  | Termination |   | +-----+      | Termination | |  | 
         |  |-------------|   | |     |      |-------------| |  | 
         |  | SCN Bearer  |   | |  *  |------| SCN Bearer  |<---+-> 
         |  |   Channel   |   | |     |      |   Channel   | |  | 
         |  +-------------+   | +-----+      +-------------+ |  | 
         |                    +------------------------------+  | 
         |                                                      | 
         |                                                      | 
         | +-------------------------------------------------+  | 
         | |Context                                          |  | 
         | |  +-------------+                +-------------+ |  | 
         | |  | Termination |   +-----+      | Termination | |  | 
         | |  |-------------|   |     |      |-------------| |  | 
       <-+--->| SCN Bearer  |---|  *  |------| SCN Bearer  |<---+-> 
         | |  |   Channel   |   |     |      |   Channel   | |  | 
         | |  +-------------+   +-----+      +-------------+ |  | 
         | +-------------------------------------------------+  | 
         | ___________________________________________________  | 
         +------------------------------------------------------+  
     
                Figure 1: Example of H.248 Connection Model 
    
   The example below shows an example of one way to accomplish a call-
   waiting scenario in a decomposed access gateway, illustrating the 
   relocation of a Termination between Contexts.   Terminations T1 and 
   T2 belong to Context C1 in a two-way audio call.  A second audio 
   call is waiting for T1 from Termination T3.  T3 is alone in Context 
   C2.  T1 accepts the call from T3, placing T2 on hold.  This action 
   results in T1 moving into Context C2, as shown below. 
    
    
     
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         +------------------------------------------------------+ 
         |Media Gateway                                         | 
         | +-------------------------------------------------+  | 
         | |Context C1                                       |  | 
         | |  +-------------+                +-------------+ |  | 
         | |  | Term. T2    |   +-----+      | Term. T1    | |  | 
         | |  |-------------|   |     |      |-------------| |  | 
       <-+--->| RTP Stream  |---|  *  |------| SCN Bearer  |<---+-> 
         | |  |             |   |     |      |   Channel   | |  | 
         | |  +-------------+   +-----+      +-------------+ |  | 
         | +-------------------------------------------------+  | 
         |                                                      | 
         | +-------------------------------------------------+  | 
         | |Context C2                                       |  | 
         | |                                 +-------------+ |  | 
         | |                    +-----+      | Term. T3    | |  | 
         | |                    |     |      |-------------| |  | 
         | |                    |  *  |------| SCN Bearer  |<---+-> 
         | |                    |     |      |   Channel   | |  | 
         | |                    +-----+      +-------------+ |  | 
         | +-------------------------------------------------+  | 
         +------------------------------------------------------+  
     
     Figure 2: Example Call Waiting Scenario / Alerting Applied to T1 
    
         +------------------------------------------------------+ 
         |Media Gateway                                         | 
         | +-------------------------------------------------+  | 
         | |Context C1                                       |  | 
         | |  +-------------+                                |  | 
         | |  | Term. T2    |   +-----+                      |  | 
         | |  |-------------|   |     |                      |  | 
       <-+--->| RTP Stream  |---|  *  |                      |  | 
         | |  |             |   |     |                      |  | 
         | |  +-------------+   +-----+                      |  | 
         | +-------------------------------------------------+  | 
         |                                                      | 
         | +-------------------------------------------------+  | 
         | |Context C2                                       |  | 
         | |  +-------------+                +-------------+ |  | 
         | |  | Term. T1    |   +-----+      | Term. T3    | |  | 
         | |  |-------------|   |     |      |-------------| |  | 
       <-+--->| SCN Bearer  |---|  *  |------| SCN Bearer  |<---+-> 
         | |  |   Channel   |   |     |      |   Channel   | |  | 
         | |  +-------------+   +-----+      +-------------+ |  | 
         | +-------------------------------------------------+  | 
         +------------------------------------------------------+ 
          
          Figure 3. Example Call Waiting Scenario / Answer by T1 
    
    
     
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6.1     Contexts 
    
   A Context is an association between a number of Terminations.  The 
   Context describes the topology (who hears/sees whom) and the media 
   mixing and/or switching parameters if more than two Terminations are 
   involved in the association. 
    
   There is a special Context called the null Context. It contains 
   Terminations that are not associated to any other Termination.  
   Terminations in the null Context can have their parameters examined 
   or modified, and may have events detected on them. 
    
   In general, an Add command is used to add Terminations to Contexts.  
   If the MGC does not specify an existing Context to which the 
   Termination is to be added, the MG creates a new Context.  A 
   Termination may be removed from a Context with a Subtract command, 
   and a Termination may be moved from one Context to another with a 
   Move command. A Termination SHALL exist in only one Context at a 
   time. 
    
   The maximum number of Terminations in a Context is a MG property. 
   Media gateways that offer only point-to-point connectivity might 
   allow at most two Terminations per Context. Media gateways that 
   support multipoint conferences might allow three or more 
   terminations per Context. 
    
6.1.1   Context Attributes and Descriptors 
    
   The attributes of Contexts are: 
    
   ¦    ContextID. A wildcarding mechanism using two types of wildcards 
   can be used with ContextIDs.  The two wildcards are ALL and CHOOSE.  
   The former is used to address ALL (except the NULL context) Contexts 
   at once in a command request and/or reply, while the latter is used 
   to indicate to a media gateway that it must create a Context. 
      
   ¦    The topology (who hears/sees whom). 
    
   The topology of a Context describes the flow of media between the 
   Terminations within a Context.  In contrast, the mode of a 
   Termination (send/receive/...) describes the flow of the media at 
   the ingress/egress of the media gateway. 
    
   ¦    The priority is used for a context in order to provide the MG 
   with information about a certain precedence handling for a context. 
   The MGC can also use the priority to control autonomously the 
   traffic precedence in the MG in a smooth way in certain situations 
   (e.g. restart), when a lot of contexts must be handled 
   simultaneously. Priority 0 is the lowest priority and a priority of 
   15 is the highest priority. 
    
   ¦    An indicator for an emergency call is also provided to allow a 
   preference handling in the MG. 
    
     
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   ¦    Additional Context attributes may be defined using the package 
   definition mechanism, hence by specifying that properties are 
   defined as ContextAttributes. 
    
6.1.2   Creating, Deleting and Modifying Contexts 
    
   The protocol can be used to (implicitly) create Contexts and modify 
   the parameter values of existing Contexts.  The protocol has 
   commands to add Terminations to Contexts, subtract them from 
   Contexts, and to move Terminations between Contexts.  Contexts are 
   deleted implicitly when the last remaining Termination is subtracted 
   or moved out. 
    
6.2     Terminations 
    
   A Termination is a logical entity on a MG that sources and/or sinks 
   media and/or control streams.  A Termination is described by a 
   number of characterizing Properties, which are grouped in a set of 
   Descriptors that are included in commands. Terminations have unique 
   identities (TerminationIDs), assigned by the MG at the time of their 
   creation. 
    
   Terminations representing physical entities have a semi-permanent 
   existence.  For example, a Termination representing a TDM channel 
   might exist for as long as it is provisioned in the gateway.  
   Terminations representing ephemeral information flows, such as RTP 
   flows, would usually exist only for the duration of their use. 
    
   Ephemeral Terminations are created by means of an Add command.  They 
   are destroyed by means of a Subtract command.  In contrast, when a 
   physical Termination is Added to or Subtracted from a Context, it is 
   taken from or to the null Context, respectively. 
    
   Terminations may have signals applied to them (see 7.1.11).    
   Terminations may be programmed to detect Events, the occurrence of 
   which can trigger notification messages to the MGC, or action by the 
   MG.  Statistics may be accumulated on a Termination.  Statistics are 
   reported to the MGC upon request (by means of the AuditValue 
   command, see section 7.2.5) and when the Termination is taken out of 
   the call it is in. 
    
   Multimedia gateways may process multiplexed media streams.  For 
   example, Recommendation H.221 describes a frame structure for 
   multiple media streams multiplexed on a number of digital 64 kbit/s 
   channels.  Such a case is handled in the connection model in the 
   following way.  For every bearer channel that carries part of the 
   multiplexed streams, there is a Termination.  The Terminations that 
   source/sink the digital channels are connected to a separate 
   Termination called the multiplexing Termination. This Termination 
   describes the multiplex used (e.g. how the H.221 frames are carried 
   over the digital channels used).  The MuxDescriptor is used to this 
   end.  If multiple media are carried, this Termination contains 
   multiple StreamDescriptors. The media streams can be associated with 
   streams sourced/sunk by other Terminations in the Context. 
     
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   Terminations may be created which represent multiplexed bearers, 
   such as an ATM AAL Type 2 bearer.  When a new multiplexed bearer is 
   to be created, an ephemeral termination is created in a context 
   established for this purpose.  When the termination is subtracted, 
   the multiplexed bearer is destroyed. 
    
6.2.1   Termination Dynamics 
    
   The protocol can be used to create new Terminations and to modify 
   property values of existing Terminations.  These modifications 
   include the possibility of adding or removing events and/or signals.  
   The Termination properties, and events and signals are described in 
   the ensuing sections. An MGC can only release/modify terminations 
   and the resources that the termination represents which it has 
   previously seized via, e.g., the Add command. 
    
6.2.2   TerminationIDs 
    
   Terminations are referenced by a TerminationID, which is an 
   arbitrary schema chosen by the MG. 
    
   TerminationIDs of physical Terminations are provisioned in the Media 
   Gateway. The TerminationIDs may be chosen to have structure.  For 
   instance, a TerminationID may consist of trunk group and a trunk 
   within the group. 
    
   A wildcarding mechanism using two types of wildcards can be used 
   with TerminationIDs.  The two wildcards are ALL and CHOOSE.  The 
   former is used to address multiple Terminations at once, while the 
   latter is used to indicate to a media gateway that it must select a 
   Termination satisfying the partially specified TerminationID.  This 
   allows, for instance, that a MGC instructs a MG to choose a circuit 
   within a trunk group. 
    
   When ALL is used in the TerminationID of a command, the effect is 
   identical to repeating the command with each of the matching 
   TerminationIDs. The use of ALL does not address the ROOT 
   termination. Since each of these commands may generate a response, 
   the size of the entire response may be large.  If individual 
   responses are not required, a wildcard response may be requested.  
   In such a case, a single response is generated, which contains the 
   UNION of all of the individual responses which otherwise would have 
   been generated, with duplicate values suppressed.    For instance, 
   given a Termination Ta with properties p1=a, p2=b and Termination Tb 
   with properties p2=c, p3=d, a UNION response would consist of a 
   wildcarded TerminationId and the sequence of properties p1=a, p2=b,c 
   and p3=d.  Wildcard response may be particularly useful in the Audit 
   commands. 
    
   The encoding of the wildcarding mechanism is detailed in Annexes A 
   and B. 
    
     
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6.2.3   Packages 
    
   Different types of gateways may implement Terminations that have 
   widely differing characteristics.  Variations in Terminations are 
   accommodated in the protocol by allowing Terminations to have 
   optional Properties, Events, Signals and Statistics implemented by 
   MGs. Contexts may also have different properties associated with 
   them. 
    
   In order to achieve MG/MGC interoperability, such options are 
   grouped into Packages, and typicallya Termination realizes a set of 
   such Packages. A context may also realize a set of Packages. More 
   information on definition of packages can be found in section 12.  
   An MGC can audit a Termination or Context  to determine which 
   Packages it realizes. 
    
   Properties, Events, Signals and Statistics defined in Packages, as 
   well as parameters to them, are referenced by identifiers (Ids).  
   Identifiers are scoped. For each package, PropertyIds, EventIds, 
   SignalIds, StatisticsIds and ParameterIds have unique name spaces 
   and the same identifier may be used in each of them.  Two 
   PropertyIds in different packages may also have the same identifier, 
   etc. 
    
   To support a particular package the MG must support all Properties, 
   Signals, Events and Statistics defined in a package. It must also 
   support all Signal and Event parameters. The MG may support a subset 
   of the values listed in a package for a particular Property or 
   Parameter. 
    
6.2.4   Termination Properties and Descriptors 
    
   Terminations have properties.  The properties have unique 
   PropertyIDs.  Most properties have default values, which are 
   explicitly defined in this standard or in a package (see Section 12) 
   or set by provisioning.  If not provisioned otherwise, the 
   properties in all descriptors except TerminationState and 
   LocalControl default to empty/"no value" when a Termination is first 
   created or returned to the null Context.  The default contents of 
   the two exceptions are described in sections 7.1.5 and 7.1.7. 
    
   The provisioning of a property value in the MG will override any 
   default value, be it supplied in this standard or a package.  
   Therefore if it is essential for the MGC to have full control over 
   the property values of a Termination, it should supply explicit 
   values when ADDing the Termination to a Context.  Alternatively, for 
   a physical Termination the MGC can determine any provisioned 
   property values by auditing the Termination while it is in the NULL 
   Context. 
    
   There are a number of common properties for Terminations and 
   properties specific to media streams. The common properties are also 
   called the termination state properties.  For each media stream, 
     
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   there are local properties and properties of the received and 
   transmitted flows.   
    
   Properties not included in the base protocol are defined in 
   Packages.  These properties are referred to by a name consisting of 
   the PackageName and a PropertyId.  Most properties have default 
   values described in the Package description. Properties may be read-
   only or read/write.  The possible values of a property may be 
   audited, as can their current values.  For properties that are 
   read/write, the MGC can set their values.  A property may be 
   declared as ŸGlobal÷ which has a single value shared by all 
   terminations realizing the package.  Related properties are grouped 
   into descriptors for convenience.  
    
   When a Termination is Added to a Context, the value of its 
   read/write properties can be set by including the appropriate 
   descriptors as parameters to the Add command.  Similarly, a property 
   of a Termination in a Context may have its value changed by the 
   Modify command.  Properties may also have their values changed when 
   a Termination is moved from one Context to another as a result of a 
   Move command.  In some cases, descriptors are returned as output 
   from a command. 
    
   In general, if a Descriptor is completely omitted from one of the 
   aforementioned Commands, the properties in that Descriptor retain 
   their prior values for the Termination(s) the Command acts on. On 
   the other hand, if some properties are omitted from a Descriptor in 
   a Command “ i.e., the Descriptor is only partially specified “ those 
   properties will be removed/reset for the Termination(s) the Command 
   acts on. For more details, see section 7.1 dealing with the 
   individual Descriptors. 
    
   The following table lists all of the possible Descriptors and their 
   use.  Not all descriptors are legal as input or output parameters to 
   every command. 
    
   Descriptors  
    
   Descriptor Name     Description 
   Modem               Identifies modem type and properties when 
                       applicable 
   Mux                 Describes multiplex type for multimedia 
                       terminations (e.g. H.221, H.223, H.225.0) and 
                       Terminations forming the input mux 
   Media               A list of media stream specifications (see 
                       7.1.4) 
   TerminationState    Properties of a Termination (which can be 
                       defined in Packages) that are not stream 
                       specific 
   Stream              A list of remote/local/localControl descriptors 
                       for a single stream 
   Local               Contains properties that specify the media flows 
                       that the MG receives from the remote entity. 
     
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   Remote              Contains properties that specify the media flows 
                       that the MG sends to the remote entity. 
   LocalControl        Contains properties (which can be defined in 
                       packages) that are of interest between the MG 
                       and the MGC 
   Events              Describes events to be detected by the MG and 
                       what to do when an event is detected 
   EventBuffer         Describes events to be detected by the MG when 
                       Event Buffering is active 
   Signals             Describes signals (see 7.1.11) applied to 
                       Terminations 
   Audit               In Audit commands, identifies which information 
                       is desired 
   Packages            In AuditValue, returns a list of Packages 
                       realized by Termination 
   DigitMap            Defines patterns against which sequences of a 
                       specified set of events are to be matched so 
                       they can be reported as a group rather than 
                       singly 
   ServiceChange       In ServiceChange, what, why service change 
                       occurred, etc.  
   ObservedEvents      In Notify or AuditValue, report of events 
                       observed 
   Statistics          In Subtract and Audit, Report of Statistics kept 
                       on a Termination 
   Topology            Specifies flow directions between Terminations 
                       in a Context 
   Error               Contains and error code and optionally error 
                       text; it may occur in command replies and in 
                       Notify requests 
    
6.2.5   Root Termination 
    
   Occasionally, a command must refer to the entire gateway, rather 
   than a termination within it.  A special TerminationID, "Root" is 
   reserved for this purpose.  Packages may be defined on Root.  Root 
   thus may have properties, events, signals and statistics.  
   Accordingly, the root TerminationID may appear in: 
    
   ¦    a Modify command - to change a property, send a signal or set 
   an event 
    
   ¦    a Notify command - to report an event 
    
   ¦    an AuditValue return - to examine the values of properties and 
   statistics implemented on root 
    
   ¦    an AuditCapability - to determine what properties of root are 
   implemented 
    
   ¦    a ServiceChange - to declare the gateway in or out of service 
      
     
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   Any other use of the root TerminationID is an error. Error code 410 
   “ Incorrect identifier shall be returned in these cases. 
    
    
7.      COMMANDS 
    
   The protocol provides commands for manipulating the logical entities 
   of the protocol connection model, Contexts and Terminations.  
   Commands provide control at the finest level of granularity 
   supported by the protocol.  For example, Commands exist to add 
   Terminations to a Context, modify Terminations, subtract 
   Terminations from a Context, and audit properties of Contexts or 
   Terminations. Commands provide for complete control of the 
   properties of Contexts and Terminations.  This includes specifying 
   which events a Termination is to report, which signals/actions are 
   to be applied to a Termination and specifying the topology of a 
   Context (who hears/sees whom). 
    
   Most commands are for the specific use of the Media Gateway 
   Controller as command initiator in controlling Media Gateways as 
   command responders.  The exceptions are the Notify and ServiceChange 
   commands: Notify is sent from Media Gateway to Media Gateway 
   Controller, and ServiceChange may be sent by either entity.  Below 
   is an overview of the commands; they are explained in more detail in 
   section 7.2. 
    
   1.   Add. The Add command adds a termination to a context.  The Add 
   command on the first Termination in a Context is used to create a 
   Context. 
    
   2.   Modify. The Modify command modifies the properties, events and 
   signals of a termination.  
    
   3.   Subtract. The Subtract command disconnects a Termination from 
   its Context and returns statistics on the Termination's 
   participation in the Context.  The Subtract command on the last 
   Termination in a Context deletes the Context. 
    
   4.   Move. The Move command atomically moves a Termination to 
   another context. 
    
   5.   AuditValue. The AuditValue command returns the current state of 
   properties, events,  signals and statistics of Terminations. 
    
   6.   AuditCapabilities. The AuditCapabilities command returns all 
   the possible values for Termination properties, events and signals 
   allowed by the Media Gateway. 
    
   7.   Notify. The Notify command allows the Media Gateway to inform 
   the Media Gateway Controller of the occurrence of events in the 
   Media Gateway. 
    
   8.   ServiceChange. The ServiceChange Command allows the Media 
   Gateway to notify the Media Gateway Controller that a Termination or 
     
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   group of Terminations is about to be taken out of service or has 
   just been returned to service.   ServiceChange is also used by the 
   MG to announce its availability to an MGC (registration), and to 
   notify the MGC of impending or completed restart of the MG.  The MGC 
   may announce a handover to the MG by sending it a ServiceChange 
   command.  The MGC may also use ServiceChange to instruct the MG to 
   take a Termination or group of Terminations in or out of service. 
   These commands are detailed in sections 7.2.1 through 7.2.8.  
    
7.1     Descriptors 
    
   The parameters to a command are termed Descriptors. A Descriptor 
   consists of a name and a list of items. Some items may have values.  
   Many Commands share common Descriptors.  This subsection enumerates 
   these Descriptors.  Descriptors may be returned as output from a 
   command.  In any such return of descriptor contents, an empty 
   descriptor is represented by its name unaccompanied by any list.  
   Parameters and parameter usage specific to a given Command type are 
   described in the subsection that describes the Command. 
      
7.1.1   Specifying Parameters 
    
   Command parameters are structured into a number of descriptors. In 
   general, the text format of descriptors is 
   DescriptorName=<someID>{parm=value, parm=value...}.  
    
   Parameters may be fully specified, over-specified or under-
   specified: 
    
   1.   Fully specified parameters have a single, unambiguous value 
   that the command initiator is instructing the command responder to 
   use for the specified parameter. 
    
   2.   Under-specified parameters, using the CHOOSE value, allow the 
   command responder to choose any value it can support. 
    
   3.   Over-specified parameters have a list of potential values.  The 
   list order specifies the command initiator's order of preference of 
   selection.  The command responder chooses one value from the offered 
   list and returns that value to the command initiator. 
    
   If a required descriptor other than the Audit descriptor is 
   unspecified (i.e., entirely absent) from a command, the previous 
   values set in that descriptor for that termination, if any, are 
   retained.  In commands other than Subtract, a missing Audit 
   descriptor is equivalent to an empty Audit Descriptor.  The behavior 
   of the MG with respect to unspecified parameters within a descriptor 
   varies with the descriptor concerened, as indicated in succeeding 
   sections.  Whenever a parameter is underspecified or overspecified, 
   the descriptor containing the value chosen by the responder is 
   included as output from the command. 
    
   Each command specifies the TerminationId the command operates on.  
   This TerminationId may be Ÿwildcarded÷.  When the TerminationId of a 
     
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   command is wildcarded, the effect shall be as if the command was 
   repeated with each of the TerminationIds matched.  
    
7.1.2   Modem Descriptor 
    
   The Modem descriptor specifies the modem type and parameters, if 
   any, required for use in e.g. H.324 and text conversation.  The 
   descriptor includes the following modem types: V.18, V.22, V.22bis, 
   V.32, V.32bis, V.34, V.90, V.91, Synchronous ISDN, and allows for 
   extensions.  By default, no modem descriptor is present in a 
   Termination. 
    
7.1.3   Multiplex Descriptor 
    
   In multimedia calls, a number of media streams are carried on a 
   (possibly different) number of bearers.  The multiplex descriptor 
   associates the media and the bearers. The descriptor includes the 
   multiplex type: 
    
   ¦    H.221 
    
   ¦    H.223, 
    
   ¦    H.226, 
    
   ¦    V.76, 
    
   ¦    Possible Extensions 
    
   and a set of TerminationIDs representing the multiplexed inputs, in 
   order.  For example: 
    
   Mux = H.221{ MyT3/1/2, MyT3/2/13, MyT3/3/6, MyT3/21/22} 
    
7.1.4   Media Descriptor 
    
   The Media Descriptor specifies the parameters for all the media 
   streams.  These parameters are structured into two descriptors, a 
   Termination State Descriptor, which specifies the properties of a 
   termination that are not stream dependent, and one or more Stream 
   Descriptors each of which describes a single media stream.  
    
   A stream is identified by a StreamID.  The StreamID is used to link 
   the streams in a Context that belong together. Multiple streams 
   exiting a termination shall be synchronized with each other.  Within 
   the Stream Descriptor, there are up to three subsidiary descriptors, 
   LocalControl, Local, and Remote. The relationship between these 
   descriptors is thus: 
    
   Media Descriptor 
        TerminationStateDescriptor 
        Stream Descriptor 
                LocalControl Descriptor 
                Local Descriptor 
     
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                Remote Descriptor 
    
   As a convenience a LocalControl, Local, or Remote descriptors may be 
   included in the Media Descriptor without an enclosing Stream 
   descriptor.  In this case, the StreamID is assumed to be 1. 
    
7.1.5   Termination State Descriptor 
    
   The Termination State Descriptor contains the ServiceStates 
   property, the EventBufferControl property and properties of a 
   termination (defined in Packages) that are not stream specific. 
    
   The ServiceStates property describes the overall state of the 
   termination (not stream-specific).  A Termination can be in one of 
   the following states: "test", "out of service", or "in service".  
   The Ÿtest÷ state indicates that the termination is being tested. The 
   state Ÿout of service÷ indicates that the termination cannot be used 
   for traffic.  The state Ÿin service÷ indicates that a termination 
   can be used or is being used for normal traffic.  "in service" is 
   the default state.  
    
   Values assigned to Properties may be simple values 
   (integer/string/enumeration) or may be underspecified, where more 
   than one value is supplied and the MG may make a choice: 
    
   ¹    Alternative Values “ multiple values in a list, one of which 
   must be selected 
    
   ¹    Ranges “ minimum and maximum values, any value between min and 
   max must be selected, boundary values included 
    
   ¹    Greater Than/Less Than “ value must be greater/less than 
   specified value 
    
   ¹    CHOOSE Wildcard “ the MG chooses from the allowed values for 
   the property 
    
   The EventBufferControl property  specifies whether events are 
   buffered following detection of an event in the Events Descriptor, 
   or processed immediately.  See section 7.1.9 for details. 
    
7.1.6   Stream Descriptor 
    
   A Stream descriptor specifies the parameters of a single bi-
   directional stream.  These parameters are structured into three 
   descriptors: one that contains termination properties specific to a 
   stream and one each for local and remote flows. The Stream 
   Descriptor includes a StreamID which identifies the stream.  Streams 
   are created by specifying a new StreamID on one of the terminations 
   in a Context. A stream is deleted by setting empty Local and Remote 
   descriptors for the stream with ReserveGroup and ReserveValue in 
   LocalControl set to "false" on all terminations in the context that 
   previously supported that stream. 
    
     
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   StreamIDs are of local significance between MGC and MG and they are 
   assigned by the MGC.  Within a context, StreamID is a means by which 
   to indicate which media flows are interconnected:  streams with the 
   same StreamID are connected. 
    
   If a termination is moved from one context to another, the effect on 
   the context to which the termination is moved is the same as in the 
   case that a new termination were added with the same StreamIDs as 
   the moved termination. 
    
7.1.7   LocalControl Descriptor 
    
   The LocalControl Descriptor contains the Mode property, the 
   ReserveGroup and ReserveValue properties and properties of a 
   termination (defined in Packages) that are stream specific, and are 
   of interest between the MG and the MGC.  Values of properties may be 
   underspecified as in section 7.1.1. 
    
   The allowed values for the mode property are send-only, receive-
   only, send/receive, inactive and loop-back.  "Send" and "receive" 
   are with respect to the exterior of the context, so that, for 
   example, a stream set to mode=sendonly does not pass received media 
   into the context. The default value for the mode property is 
   "Inactive".  Signals and Events are not affected by mode. 
    
   The boolean-valued Reserve properties, ReserveValue and 
   ReserveGroup, of a Termination indicate what the MG is expected to 
   do when it receives a  local and/or remote descriptor.  
    
   If the value of a Reserve property is True, the MG SHALL reserve 
   resources for all alternatives specified in the local and/or remote 
   descriptors for which it currently has resources available.  It 
   SHALL respond with the alternatives for which it reserves resources.  
   If it cannot not support any of the alternatives, it SHALL respond 
   with a reply to the MGC that contains empty local and/or remote 
   descriptors. 
    
   If the value of a Reserve property is False, the MG SHALL choose one 
   of the alternatives specified in the local descriptor (if present) 
   and one of the alternatives specified in the remote descriptor (if 
   present).  If the MG has not yet reserved resources to support the 
   selected alternative, it SHALL reserve the resources.  If, on the 
   other hand, it already reserved resources for the Termination 
   addressed (because of a prior exchange with ReserveValue and/or 
   ReserveGroup equal to True), it SHALL release any excess resources 
   it reserved previously.  Finally, the MG shall send a reply to the 
   MGC containing the alternatives for the local and/or remote 
   descriptor that it selected.  If the MG does not have sufficient 
   resources to support any of the alternatives specified, is SHALL 
   respond with error 510 (insufficient resources). 
    
   The default value of ReserveValue and ReserveGroup is False.  More 
   information on the use of the two Reserve properties is provided in 
   section 7.1.8. 
     
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   A new setting of the LocalControl Descriptor completely replaces the 
   previous setting of that descriptor in the MG.  Thus to retain 
   information from the previous setting the MGC must include that 
   information in the new setting.  If the MGC wishes to delete some 
   information from the existing descriptor, it merely resends the 
   descriptor (in a Modify command) with the unwanted information 
   stripped out. 
    
7.1.8   Local and Remote Descriptors 
    
   The MGC uses Local and Remote descriptors to reserve and commit MG 
   resources for media decoding and encoding for the given Stream(s) 
   and Termination to which they apply.  The MG includes these 
   descriptors in its response to indicate what it is actually prepared 
   to support.  The MG SHALL include additional properties and their 
   values in its response if these properties are mandatory yet not 
   present in the requests made by the MGC (e.g., by specifying 
   detailed video encoding parameters where the MGC only specified the 
   payload type). 
    
   Local refers to the media received by the MG and Remote refers to 
   the media sent by the MG. 
    
   When text encoding the protocol, the descriptors consist of session 
   descriptions as defined in SDP (RFC2327).  In session descriptions 
   sent from the MGC to the MG, the following exceptions to the syntax 
   of RFC 2327 are allowed: 
    
   ¹    the "s=", "t=" and "o=" lines are optional, 
    
   ¹    the use of CHOOSE is allowed in place of a single parameter 
   value, and 
    
   ¹    the use of alternatives is allowed in place of a single 
   parameter value.  
    
   A Stream Descriptor specifies a single bi-directional media stream 
   and so a single session description MUST NOT include more than one 
   media description ("m=" line).  Any additional media streams for a 
   termination must appear in distinct Stream Descriptors.  When 
   multiple session descriptions are provided in one descriptor, the 
   "v=" lines are required as delimiters; otherwise they are optional 
   in session descriptions sent to the MG.  Implementations shall 
   accept session descriptions that are fully conformant to RFC2327. 
   When binary encoding the protocol the descriptor consists of groups 
   of properties (tag-value pairs) as specified in Annex C.  Each such 
   group may contain the parameters of a session description. 
    
   Below, the semantics of the local and remote descriptors are 
   specified in detail.  The specification consists of two parts.  The 
   first part specifies the interpretation of the contents of the 
   descriptor.  The second part specifies the actions the MG must take 
   upon receiving the local and remote descriptors.  The actions to be 
     
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   taken by the MG depend on the values of the ReserveValue and 
   ReserveGroup properties of the LocalControl descriptor. 
    
   Either the local or the remote descriptor or both may be  
    
   ¹    unspecified (i.e., absent),  
    
   ¹    empty,  
    
   ¹    underspecified through use of CHOOSE in a property value, 
     
   ¹    fully specified, or 
    
   ¹    overspecified through presentation of multiple groups of 
   properties and possibly multiple property values in one or more of 
   these groups. 
    
   Where the descriptors have been passed from the MGC to the MG, they 
   are interpreted according to the rules given in section 7.1.1, with 
   the following additional comments for clarification: 
    
   (a)  An unspecified Local or Remote descriptor is considered to be a 
   missing mandatory parameter.  It requires the MG to use whatever was 
   last specified for that descriptor.  It is possible that there was 
   no previously-specified value, in which case the descriptor 
   concerned is ignored in further processing of the command. 
    
   (b)  An empty Local (Remote) descriptor in a message from the MGC 
   signifies a request to release any resources reserved for the media 
   flow received (sent). 
    
   (c)  If multiple groups of properties are present in a Local or 
   Remote descriptor or multiple values within a group, the order of 
   preference is descending. 
    
   (d)  Underspecified or overspecified properties within a group of 
   properties sent by the MGC are requests for  the MG to choose one or 
   more values which it can support for each of those properties.  In 
   case of an overspecified property, the list of values is in 
   descending order of preference. 
    
   Subject to the above rules, subsequent action depends on the values 
   of the ReserveValue and ReserveGroup properties in LocalControl.   
    
   If ReserveGroup is true, the MG reserves the resources required to 
   support any of the requested property group alternatives that it can 
   currently support.  If ReserveValue is true, the MG reserves the 
   resources required to support any of the requested property value 
   alternatives that it can currently support. 
    
   NOTE “ If a Local or Remote descriptor contains multiple groups of 
   properties, and ReserveGroup is true, then the MG is requested to 
   reserve resources so that it can decode or encode the media stream 
   according to any of the alternatives.  For instance, if the Local 
     
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   descriptor contains two groups of properties, one specifying 
   packetized G.711 A-law audio and the other G.723.1 audio, the MG 
   reserves resources so that it can decode one audio stream encoded in 
   either G.711 A-law format or G.723.1 format.  The MG does not have 
   to reserve resources to decode two audio streams simultaneously, one 
   encoded in G.711 A-law and one in G.723.1.  The intention for the 
   use of  ReserveValue is analogous. 
    
   If ReserveGroup is true or ReserveValue is true, then the following 
   rules apply. 
    
   ¦    If the MG has insufficient resources to support all 
   alternatives requested by the MGC and the MGC requested resources in 
   both Local and Remote,  the MG should reserve resources to support 
   at least one alternative each within Local and Remote. 
    
   ¦    If the MG has insufficient resources to support at least one 
   alternative  within a Local  (Remote) descriptor received from the 
   MGC, it shall return an empty Local (Remote) in response. 
    
   ¦    In its response to the MGC, when the MGC included Local and 
   Remote descriptors, the MG SHALL include Local and Remote 
   descriptors for all groups of properties and property values it 
   reserved resources for.  If the MG is incapable of supporting at 
   least one of the alternatives within the Local (Remote) descriptor 
   received from the MGC, it SHALL return an empty Local (Remote) 
   descriptor. 
    
   ¦    If the Mode property of the LocalControl descriptor is 
   RecvOnly, SendRecv, or LoopBack, the MG must be prepared to receive 
   media encoded according to any of the alternatives included in its 
   response to the MGC. 
    
   If ReserveGroup is False and ReserveValue is false, then the MG 
   SHOULD apply the following rules to resolve Local and Remote to a 
   single alternative each: 
    
   ¦    The MG chooses the first alternative in Local for which it is 
   able to support at least one alternative in Remote.  
     
   ¦    If the MG is unable to support at least one Local and one 
   Remote alternative, it returns Error 510 (Insufficient Resources). 
    
   ¦    The MG returns its selected alternative in each of Local and 
   Remote. 
    
   A new setting of a Local or Remote Descriptor completely replaces 
   the previous setting of that descriptor in the MG.  Thus to retain 
   information from the previous setting the MGC must include that 
   information in the new setting.  If the MGC wishes to delete some 
   information from the existing descriptor, it merely resends the 
   descriptor (in a Modify command) with the unwanted information 
   stripped out.  
     
     
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7.1.9   Events Descriptor  
    
   The EventsDescriptor parameter contains a RequestIdentifier and a 
   list of events that the Media Gateway is requested to detect and 
   report.  The RequestIdentifier is used to correlate the request with 
   the notifications that it may trigger.  Requested events include, 
   for example, fax tones, continuity test results, and on-hook and 
   off-hook transitions. The RequestIdentifier is omitted if the 
   EventsDescriptor is empty (i.e. no events are specified). 
    
   Each event in the descriptor contains the Event name, an optional 
   streamID, an optional KeepActive flag, and optional parameters.  The 
   Event name consists of a Package Name (where the event is defined) 
   and an EventID. The ALL wildcard may be used for the EventID, 
   indicating that all events from the specified package have to be 
   detected.  The default streamID is 0, indicating that the event to 
   be detected is not related to a particular media stream.  Events can 
   have parameters.  This allows a single event description to have 
   some variation in meaning without creating large numbers of 
   individual events.  Further event parameters are defined in the 
   package.   
    
   If a digit map completion event is present or implied in the 
   EventsDescriptor, the EventDM parameter is used to carry either the 
   name or the value of the associated digit map.  See section 7.1.14 
   for further details. 
    
   When an event is processed against the contents of an active Events 
   descriptor and found to be present in that descriptor 
   ("recognized"), the default action of the MG is to send a Notify 
   command to the MGC.  Notification may be deferred if the event is 
   absorbed into the current dial string of an active digit map (see 
   section 7.1.14).  Any other action is for further study.  Moreover, 
   event recognition may cause currently active signals to stop, or may 
   cause the current Events and/or Signals descriptor to be replaced, 
   as described at the end of this section. Unless the events 
   descriptor is replaced by another events descriptor, it remains 
   active after an event has been recognized. 
    
   If the value of the EventBufferControl property equals LockStep, 
   following detection of such an event, normal handling of events is 
   suspended. Any event which is subsequently detected and occurs in 
   the EventBuffer Descriptor is added to the end of the EventBuffer (a 
   FIFO queue), along with the time that it was detected.   The MG 
   SHALL wait for a new EventsDescriptor to be loaded.  A new 
   EventsDescriptor can be loaded either as the result of receiving a 
   command with a new EventsDescriptor, or by activating an embedded 
   EventsDescriptor. 
    
   If EventBufferControl equals Off, the MG continues processing based 
   on the active EventsDescriptor. 
    
   In the case that an embedded EventsDescriptor being activated, the 
   MG continues event processing based on the newly activated 
     
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   EventsDescriptor (Note - for purposes of EventBuffer handling, 
   activation of an embedded EventsDescriptor is equivalent to receipt 
   of a new EventsDescriptor). 
    
   When the MG receives a command with a new EventsDescriptor, one or 
   more events may have been buffered in the EventBuffer in the MG. The 
   value of EventBufferControl then determines how the MG treats such 
   buffered events. 
    
   Case 1 
    
   If EventBufferControl equals LockStep  and the MG receives a new 
   EventsDescriptor it will check the FIFO EventBuffer and take the 
   following actions: 
    
   1.   If the EventBuffer is empty, the MG waits for detection of 
   events based on the new EventsDescriptor. 
    
   2.   If the EventBuffer is non-empty, the MG processes the FIFO 
   queue starting with the first event: 
    
   a)   If the event in the queue is in the events listed in the new 
   EventsDescriptor, the MG acts on the event and removes the event 
   from the EventBuffer.  The time stamp of the Notify shall be the 
   time the event was actually detected.  The MG then waits for a new 
   EventsDescriptor. While waiting for a new EventsDescriptor, any 
   events detected that appear in the EventsBufferDescriptor will be 
   placed in the EventBuffer.  When a new EventsDescriptor is received, 
   the event processing will repeat from step 1. 
    
   b)   If the event is not in the new EventsDescriptor, the MG SHALL 
   discard the event and repeat from step 1. 
    
   Case 2 
    
   If EventBufferControl equals Off and the MG receives a new 
   EventsDescriptor, it processes new events with the new 
   EventsDescriptor. 
    
   If the MG receives a command instructing it to set the value of 
   EventBufferControl to Off, all events in the EventBuffer SHALL be 
   discarded. 
    
   The MG may report several events in a single Transaction as long as 
   this does not unnecessarily delay the reporting of individual 
   events. 
    
   For procedures regarding transmitting the Notify command, refer to 
   the appropriate annex for specific transport considerations. 
    
   The default value of EventBufferControl is Off. 
    
   Note “ Since the EventBufferControl property is in the 
   TerminationStateDescriptor, the MG might receive a command that 
     
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   changes the EventBufferControl property and does not include an 
   EventsDescriptor. 
    
   Normally, recognition of an event shall cause any active signals to 
   stop.  When KeepActive is specified in the event, the MG shall not 
   interrupt any signals active on the Termination on which the event 
   is detected. 
    
   An event can include an Embedded Signals descriptor and/or an 
   Embedded Events Descriptor which, if present, replaces the current 
   Signals/Events descriptor when the event is recognized.  It is 
   possible, for example, to specify that the dial-tone Signal be 
   generated when an off-hook Event is recognized, or that the dial-
   tone Signal be stopped when a digit is recognized.  A media gateway 
   controller shall not send EventsDescriptors with an event both 
   marked KeepActive and containing an embedded SignalsDescriptor. 
    
   Only one level of embedding is permitted.  An  embedded 
   EventsDescriptor SHALL NOT contain another embedded 
   EventsDescriptor; an embedded EventsDescriptor may contain an 
   embedded SignalsDescriptor. 
    
   An EventsDescriptor received by a media gateway replaces any 
   previous Events Descriptor.  Event notification in process shall 
   complete, and events detected after the command containing the new 
   EventsDescriptor executes, shall be processed according to the new 
   EventsDescriptor. 
    
   An empty Events Descriptor disables all event recognition and 
   reporting.  An empty EventBuffer Descriptor clears the EventBuffer 
   and disables all event accumulation in LockStep mode: the only 
   events reported will be those occurring while an Events Descriptor 
   is active.  If an empty Events Descriptor is activated while the 
   termination is operating in LockStep mode, the events buffer is 
   immediately cleared. 
    
7.1.10  EventBuffer Descriptor 
    
   The EventBuffer Descriptor contains a list of events, with their 
   parameters if any, that the MG is requested to detect and buffer 
   when EventBufferControl equals LockStep (see 7.1.9).   
    
7.1.11  Signals Descriptor  
    
   Signals are MG generated media streams such as tones and 
   announcements as well as line signals such as hookswitch. More 
   complex signals may include a sequence of such simple signals 
   interspersed with and conditioned upon the receipt and analysis of 
   received media data and bearer-related signals (such as echoing of 
   received data). 
    
   A SignalsDescriptor is a parameter that contains the set of signals 
   that the Media Gateway is asked to apply to a Termination. A 
   SignalsDescriptor contains a number of signals and/or sequential 
     
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   signal lists.  A SignalsDescriptor may contain zero signals and 
   sequential signal lists.  Support of sequential signal lists is 
   optional. 
    
   Signals are defined in packages.  Signals shall be named with a 
   Package name (in which the signal is defined) and a SignalID.  No 
   wildcard shall be used in the SignalID.  Signals that occur in a 
   SignalsDescriptor have an optional StreamID parameter (default is 0, 
   to indicate that the signal is not related to a particular media 
   stream), an optional signal type (see below), an optional duration 
   and possibly parameters defined in the package that defines the 
   signal.  This allows a single signal to have some variation in 
   meaning, obviating the need to create large numbers of individual 
   signals. 
    
   Finally, the optional parameter "notifyCompletion" allows a MGC to 
   indicate that it wishes to be  notified when the signal finishes 
   playout.  The possible cases are that the signal timed out (or 
   otherwise completed on its own), that it was interrupted by an 
   event, that it was halted when a Signals Descriptor was replaced, or 
   that it stopped or never started for other reasons.  If the 
   notifyCompletion parameter is not included in a Signals Descriptor, 
   notification is generated only if the signal stopped or was never 
   started for other reasons.  For reporting to occur, the signal 
   completion event (see section E.1.2) must be enabled in the 
   currently active Events Descriptor. 
    
   The duration is an integer value that is expressed in hundredths of 
   a second. 
    
   There are three types of signals: 
    
   ¦    on/off “ the signal lasts until it is turned off, 
    
   ¦    timeout “ the signal lasts until it is turned off or a specific 
   period of time elapses, 
    
   ¦    brief “ the signal duration is so short that it will stop on 
   its own unless a new signal is applied that causes it to stop; no 
   timeout value is needed. 
    
   If the signal type is specified in a SignalsDescriptor, it overrides 
   the default signal type (see Section 12.1.4). If duration is 
   specified for an on/off signal, it SHALL be ignored. 
    
   A sequential signal list consists of a signal list identifier and a 
   sequence of signals to be played sequentially.  Only the trailing 
   element of the sequence of signals in a sequential signal list may 
   be an on/off signal. The duration of a sequential signal list is the 
   sum of the durations of the signals it contains.   
    
   Multiple signals and sequential signal lists in the same 
   SignalsDescriptor shall be played simultaneously. 
    
     
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   Signals are defined as proceeding from the termination towards the 
   exterior of the Context unless otherwise specified in a package.  
   When the same Signal is applied to multiple Terminations within one 
   Transaction, the MG should consider using the same resource to 
   generate these Signals.  
    
   Production of a Signal on a Termination is stopped by application of 
   a new SignalsDescriptor, or detection of an Event on the Termination 
   (see section 7.1.9). 
    
   A new SignalsDescriptor replaces any existing SignalsDescriptor.  
   Any signals applied to the Termination not in the replacement 
   descriptor shall be stopped, and new signals are applied, except as 
   follows.  Signals present in the replacement descriptor and 
   containing the KeepActive flagshall be continued if they are 
   currently playing and have not already completed.  If a replacement 
   signal descriptor contains a signal that is not currently playing 
   and contains the KeepActive flag, that signal SHALL be ignored.  If 
   the replacement descriptor contains a sequential signal list with 
   the same identifier as the existing descriptor, then 
    
   ¹    the signal type and sequence of signals in the sequential 
   signal list in the replacement descriptor shall be ignored, and 
    
   ¹    the playing of the signals in the sequential signal list in the 
   existing descriptor shall not be interrupted. 
    
7.1.12  Audit Descriptor 
    
   The Audit Descriptor specifies what information is to be audited.  
   The Audit Descriptor specifies the list of descriptors and or 
   individual properties to be returned.  Audit may be used in any 
   command to force the return of a descriptor even if the descriptor 
   in the command was not present, or had no underspecified parameters.  
   Possible items in the Audit Descriptor are: 
    
   Modem  
   Mux  
   Events  
   Media 
   Signals  
   ObservedEvents 
   DigitMap 
   Statistics 
   Packages 
   EventBuffer 
   Individual Audit Items: 
        Media Properties 
        Modem Properties 
        Events 
        Event Buffer 
        Signals, Signal Lists 
        Digit Maps 
        Statistics 
     
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        Packages 
    
   Audit may be empty, in which case, no descriptors are returned.  
   This is useful in Subtract, to inhibit return of statistics, 
   especially when using wildcard. 
    
7.1.13  ServiceChange Descriptor 
    
   The ServiceChangeDescriptor contains the following parameters: 
    
   ¦    ServiceChangeMethod  
   ¦    ServiceChangeReason  
   ¦    ServiceChangeAddress  
   ¦    ServiceChangeDelay 
   ¦    ServiceChangeProfile 
   ¦    ServiceChangeVersion  
   ¦    ServiceChangeMGCId 
   ¦    TimeStamp 
   ¦    Extension 
    
   See section 7.2.8 
    
7.1.14  DigitMap Descriptor 
    
7.1.14.1  DigitMap Definition, Creation, Modification and Deletion 
    
   A DigitMap is a dialing plan resident in the Media Gateway used for 
   detecting and reporting digit events received on a Termination.  The 
   DigitMap Descriptor contains a DigitMap name and the DigitMap to be 
   assigned.  A digit map may be preloaded into the MG by management 
   action and referenced by name in an EventsDescriptor, may be defined 
   dynamically and subsequently referenced by name, or the actual 
   digitmap itself may be specified in the EventsDescriptor. It is 
   permissible for a digit map completion event within an Events 
   Descriptor to refer by name to a DigitMap which is defined by a 
   DigitMap Descriptor within the same command, regardless of the 
   transmitted order of the respective descriptors. 
    
   DigitMaps defined in a DigitMapDescriptor can occur in any of the 
   standard Termination manipulation Commands of the protocol.  A 
   DigitMap, once defined, can be used on all Terminations specified by 
   the (possibly wildcarded) TerminationID in such a command.  
   DigitMaps defined on the root Termination are global and can be used 
   on every Termination in the MG, provided that a DigitMap with the 
   same name has not been defined on the given Termination. When a 
   DigitMap is defined dynamically in a DigitMap Descriptor: 
    
   ¦    A new DigitMap is created by specifying a name that is not yet 
   defined.  The value shall be present. 
    
   ¦    A DigitMap value is updated by supplying a new value for a name 
   that is already defined.  Terminations presently using the digitmap 
   shall continue to use the old definition; subsequent 
   EventsDescriptors specifying the name, including any 
     
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   EventsDescriptor in the command containing the DigitMap descriptor, 
   shall use the new one. 
    
   ¦    A DigitMap is deleted by supplying an empty value for a name 
   that is already defined.  Terminations presently using the digitmap 
   shall continue to use the old definition. 
    
7.1.14.2        DigitMap Timers 
    
   The collection of digits according to a DigitMap may be protected by 
   three timers, viz. a start timer (T), short timer (S), and long 
   timer (L). 
    
   1.   The start timer (T) is used prior to any digits having been 
   dialed. 
    
   2.   If the Media Gateway can determine that at least one more digit 
   is needed for a digit string to match any of the allowed patterns in 
   the digit map, then the interdigit timer value should be set to a 
   long (L) duration (e.g. 16 seconds). 
    
   3.   If the digit string has matched one of the patterns in a digit 
   map, but it is possible that more digits could be received which 
   would cause a match with a different pattern, then instead of 
   reporting the match immediately, the MG must apply the short timer 
   (S) and wait for more digits. 
    
   The timers are configurable parameters to a DigitMap.  The Start 
   timer is started at thebeginning of every digit map use, but can be 
   overridden. 
    
7.1.14.3        DigitMap Syntax 
    
   The formal syntax of the digit map is described by the DigitMap rule 
   in the formal syntax description of the protocol (see Annex A and 
   Annex B). A DigitMap, according to this syntax, is defined either by 
   a string or by a list of strings. Each string in the list is an 
   alternative event sequence, specified either as a sequence of digit 
   map symbols or as a regular expression of digit map symbols.  These 
   digit map symbols, the digits "0" through "9" and letters "A" 
   through a maximum value depending on the signalling system 
   concerned, but never exceeding "K", correspond to specified events 
   within a package which has been designated in the Events Descriptor 
   on the termination to which the digit map is being applied.  (The 
   mapping between events and digit map symbols is defined in the 
   documentation for packages associated with channel-associated 
   signalling systems such as DTMF, MF, or R2.  Digits "0" through "9" 
   MUST be mapped to the corresponding digit events within the 
   signalling system concerned.  Letters should be allocated in logical 
   fashion, facilitating the use of range notation for alternative 
   events.)   
    
   The letter "x" is used as a wildcard, designating any event 
   corresponding to symbols in the range "0"-"9".  The string may also 
     
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   contain explicit ranges and, more generally, explicit sets of 
   symbols, designating alternative events any one of which satisfies 
   that position of the digit map.  Finally, the dot symbol "." stands 
   for zero or more repetitions of the event selector (event, range of 
   events, set of alternative events, or wildcard) that precedes it.  
   As a consequence of the third timing rule above, inter-event timing 
   while matching a terminal dot symbol uses the short timer by 
   default. 
    
   In addition to these event symbols, the string may contain "S" and 
   "L" inter-event timing specifiers and the "Z" duration modifier.  
   "S" and "L" respectively indicate that the MG should use the short 
   (S) timer or the long (L) timer for subsequent events, over-riding 
   the timing rules described above. If an explicit timing specifier is 
   in effect in one alternative event sequence, but none is given in 
   any other candidate alternative, the timer value set by the explicit 
   timing specifier must be used.  If all sequences with explicit 
   timing controls are dropped from the candidate set, timing reverts 
   to the default rules given above.  Finally, if conflicting timing 
   specifiers are in effect in different alternative sequences, the 
   results are undefined. 
    
   A "Z" designates a long duration event: placed in front of the 
   symbol(s) designating the event(s) which satisfy a given digit 
   position, it indicates that that position is satisfied only if the 
   duration of the event exceeds the long-duration threshold.  The 
   value of this threshold is assumed to be provisioned in the MG.  
    
7.1.14.4        DigitMap Completion Event 
    
   A digit map is active while the events descriptor which invoked it 
   is active and it has not completed.  A digit map completes when: 
    
   ¹    a timer has expired, or 
    
   ¹    an alternative event sequence has been matched and no other 
   alternative event sequence in the digit map could be matched through 
   detection of an additional event (unambiguous match), or 
    
   ¹    an event has been detected such that a match to a complete 
   alternative event sequence of the digit map will be impossible no 
   matter what additional events are received. 
    
   Upon completion, a digit map completion event as defined in the 
   package providing the events being mapped into the digit map shall 
   be generated.  At that point the digit map is deactivated.  
   Subsequent events in the package are processed as per the currently 
   active event processing mechanisms. 
    
7.1.14.5        DigitMap Procedures 
    
   Pending completion, successive events shall be processed according 
   to the following rules: 
    
     
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   1.   The "current dial string", an internal variable, is initially 
   empty.  The set of candidate alternative event sequences includes 
   all of the alternatives specified in the digit map. 
    
   2.   At each step, a timer is set to wait for the next event, based 
   either on the default timing rules given above or on explicit timing 
   specified in one or more alternative event sequences. If the timer 
   expires and a member of the candidate set of alternatives is fully 
   satisfied, a timeout completion with full match is reported.  If the 
   timer expires and part or none of any candidate alternative is 
   satisfied, a timeout completion with partial match is reported. 
    
   3.   If an event is detected before the timer expires, it is mapped 
   to a digit string symbol and provisionally added to the end of the 
   current dial string.  The duration of the event (long or not long) 
   is noted if and only if this is relevant in the current symbol 
   position (because at least one of the candidate alternative event 
   sequences includes the "Z" modifier at this position in the 
   sequence). 
    
   4.   The current dial string is compared to the candidate 
   alternative event sequences.  If and only if a sequence expecting a 
   long-duration event at this position is matched (i.e. the event had 
   long duration and met the specification for this position), then any 
   alternative event sequences not specifying a long duration event at 
   this position are discarded, and the current dial string is modified 
   by inserting a "Z" in front of the symbol representing the latest 
   event.  Any sequence expecting a long-duration event at this 
   position but not matching the observed event is discarded from the 
   candidate set.   If alternative event sequences not specifying a 
   long duration event in the given position remain in the candidate 
   set after application of the above rules, the observed event 
   duration is treated as irrelevant in assessing matches to them. 
    
   5.   If exactly one candidate remains and it has been fully matched, 
   a completion event is generated indicating an unambiguous match.  If 
   no candidates remain, the latest event is removed from the current 
   dial string and a completion event is generated indicating full 
   match if one of the candidates from the previous step was fully 
   satisfied before the latest event was detected, or partial match 
   otherwise.  The event removed from the current dial string will then 
   be reported as per the currently active event processing mechanisms. 
    
   6.   If no completion event is reported out of step 5 , processing 
   returns to step 2. 
    
7.1.14.6        DigitMap Activation 
    
   A digit map is activated whenever a new event descriptor is applied 
   to the termination or embedded event descriptor is activated, that 
   event descriptor contains a digit map completion event and the digit 
   map completion event contains an eventDM field in the 
   requestedactions field.  Each new activation of a digit map begins 
   at step 1 of the above procedure, with a clear current dial string.  
     
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   Any previous contents of the current dial string from an earlier 
   activation are lost. 
    
   A digit map completion event that does not contain an eventDM field 
   in its requested actions field, is considered an error.  Upon 
   receipt of such an event in an EventsDescriptor, a MG shall respond 
   with an error reponse, including error 457 “ Missing parameter in 
   signal or event. 
    
7.1.14.7        Interaction Of DigitMap and Event Processing 
    
   While the digit map is activated, detection is enabled for all 
   events defined in the package containing the specified digit map 
   completion event.  Normal event behaviour (e.g. stopping of signals 
   unless the digit completion event has the KeepActive flag enabled) 
   continues to apply for each such event detected, except that: 
    
   ¹    the events in the package containing the specified digit map 
   completion event other than the completion event itself are not 
   individually notified, and 
    
   ¹    an event that triggers a partial match completion event is not 
   recognized and therefore has no side effects until reprocessed 
   following the recognition of the digit map completion event. 
    
7.1.14.8        Wildcards 
    
   Note that if a package contains a digit map completion event, then 
   an event specification consisting of the package name with a 
   wildcarded ItemID (Property Name) will activate a digit map“ to that 
   end the event specification must include an eventDM field according 
   to section 7.1.14.6. If the package also contains the digit events 
   themselves, this form of event specification will cause the 
   individual events to be reported to the MGC as they are detected. 
    
7.1.14.9        Example 
    
   As an example, consider the following dial plan: 
   0                         Local operator 
   00                        Long distance operator 
   xxxx                      Local extension number(starts with 1-7) 
   8xxxxxxx                  Local number 
   #xxxxxxx                  Off-site extension 
   *xx                       Star services 
   91xxxxxxxxxx              Long distance number 
   9011 + up to 15 digits    International number 
    
    
   If the DTMF detection package described in Annex E (section E.6) is 
   used to collect the dialled digits, then the dialling plan shown 
   above results in the following digit map: 
     (0| 00|[1-7]xxx|8xxxxxxx|Fxxxxxxx|Exx|91xxxxxxxxxx|9011x.) 
    
     
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7.1.15  Statistics Descriptor 
    
   The Statistics parameter provides information describing the status 
   and usage of a Termination during its existence within a specific 
   Context.  There is a set of standard statistics kept for each 
   termination where appropriate (number of octets sent and received 
   for example).  The particular statistical properties that are 
   reported for a given Termination are determined by the Packages 
   realized by the Termination.  By default, statistics are reported 
   when the Termination is Subtracted from the Context.  This behavior 
   can be overridden by including an empty AuditDescriptor in the 
   Subtract command.  Statistics may also be returned from the 
   AuditValue command, or any Add/Move/Modify command using the Audit 
   descriptor. 
    
   Statistics are cumulative; reporting Statistics does not reset them.  
   Statistics are reset when a Termination is Subtracted from a 
   Context. 
    
7.1.16  Packages Descriptor 
    
   Used only with the AuditValue command, the PackageDescriptor returns 
   a list of Packages realized by the Termination. 
    
7.1.17  ObservedEvents Descriptor 
    
   ObservedEvents is supplied with the Notify command to inform the MGC 
   of which event(s) were detected.  Used with the AuditValue command, 
   the ObservedEventsDescriptor returns events in the event buffer 
   which have not been Notified. ObservedEvents contains the 
   RequestIdentifier of the EventsDescriptor that triggered the 
   notification, the event(s) detected optionally the detection time(s) 
   and any parameters of the event. Detection times are reported with a 
   precision of hundredths of a second.  Time is expressed in UTC. 
    
7.1.18   Topology Descriptor 
    
   A topology descriptor is used to specify flow directions between 
   terminations in a Context.  Contrary to the descriptors in previous 
   sections, the topology descriptor applies to a Context instead of a 
   Termination.  The default topology of a Context is that each 
   termination's transmission is received by all other terminations.  
   The Topology Descriptor is optional to implement. An MG that does 
   not support Topology descriptors, but receives a command containing 
   one, returns error Ÿ444 Unsupported or unknown descriptor÷and 
   includes a string containing the name of the unsupported Descriptor 
   (ŸTopology÷) in the error text in the error descriptor. 
    
   The Topology Descriptor occurs before the commands in an action.  It 
   is possible to have an action containing only a Topology Descriptor, 
   provided that the context to which the action applies already 
   exists. 
    
     
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   A topology descriptor consists of a sequence of associated 
   terminations of the form (T1, T2, association[,StreamId]). T1 and T2 
   specify Terminations within the Context, possibly using the ALL or 
   CHOOSE wildcard.  If the optional StreamId field is used, the 
   association applies only to the particular stream between T1 and T2 
   labeled by the StreamId. If the StreamId field is omitted the 
   topology applies to all streams in the termination.The association 
   specifies how media flows between these two Terminations as follows. 
    
   ¦    (T1, T2, isolate) means that the Terminations matching T2 do 
   not receive media from the Terminations matching T1, nor vice versa. 
    
   ¦    (T1, T2, oneway) means that the Terminations that match T2 
   receive media from the Terminations matching T1, but not vice versa.  
   In this case use of the ALL wildcard such that there are 
   Terminations that match both T1 and T2 is not allowed. 
    
   ¦    (T1, T2, bothway) means that the Terminations matching T2 
   receive media from the Terminations matching T1, and vice versa.  In 
   this case it is allowed to use wildcards such that there are 
   Terminations that match both T1 and T2.  However, if there is a 
   Termination that matches both, no loopback is introduced. 
    
   CHOOSE wildcards may be used in T1 and T2 as well, under the 
   following restrictions: 
    
   ¦    the action (see section 8) of which the topology descriptor is 
   part contains an Add command in which a CHOOSE wildcard is used; 
    
   ¦    if a CHOOSE wildcard occurs in T1 or T2, then a partial name 
   SHALL NOT be specified. 
    
   The CHOOSE wildcard in a topology descriptor matches the 
   TerminationID that the MG assigns in the first Add command that uses 
   a CHOOSE wildcard in the same action.  An existing Termination that 
   matches T1 or T2 in the Context to which a Termination is added, is 
   connected to the newly added Termination as specified by the 
   topology descriptor.  If a termination is not mentioned within a 
   topology descriptor, any topology associated with it remains 
   unchanged. If, however, a new termination is added into a context 
   its association with the other terminations within the context 
   defaults to bothway, unless a topology descriptor is given to change 
   this (eg. if T3 is added to a context with T1 and T2 with topology 
   (T3,T1,oneway) it will be connected bothway to T2). 
    
   If the topology is applied to one particular stream (T1, T2, 
   association, StreamId), the topology of other streams between the 
   terminations does not change.  
    
   A topology descriptor SHALL NOT include a combination of 
   associations between two terminations (Ti,Tj) with and without the 
   optional StreamID field, to avoid undefined behavior. For example 
   (T1,T2, bothway) and (T1,T2,isolate,S1) shall not appear in the same 
   descriptor. Upon receipt of such a topology descriptor, a MG shall 
     
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   respond with an error response, including error 421 - Unknown action 
   or illegal combination of actions. 
    
   The figure below and the table following it show some examples of 
   the effect of including topology descriptors in actions.  In these 
   examples it is assumed that the topology descriptors are applied in 
   sequence. 
    
     +------------------+  +------------------+  +------------------+ 
     |      +----+      |  |      +----+      |  |      +----+      | 
     |      | T2 |      |  |      | T2 |      |  |      | T2 |      | 
     |      +----+      |  |      +----+      |  |      +----+      | 
     |       ^  ^       |  |          ^       |  |          ^       | 
     |       |  |       |  |          |       |  |          |       | 
     |    +--+  +--+    |  |          +---+   |  |          +--+    | 
     |    |        |    |  |              |   |  |             |    | 
     |    v        v    |  |              v   |  |             |    | 
     | +----+    +----+ |  | +----+    +----+ |  | +----+    +----+ | 
     | | T1 |<-->| T3 | |  | | T1 |<-->| T3 | |  | | T1 |<-->| T3 | | 
     | +----+    +----+ |  | +----+    +----+ |  | +----+    +----+ | 
     +------------------+  +------------------+  +------------------+ 
     1. No Topology Desc.   2. T1, T2, Isolate    3. T3, T2, Oneway 
    
     +------------------+  +------------------+  +------------------+ 
     |      +----+      |  |      +----+      |  |      +----+      | 
     |      | T2 |      |  |      | T2 |      |  |      | T2 |      | 
     |      +----+      |  |      +----+      |  |      +----+      | 
     |          |       |  |          ^       |  |       ^  ^       | 
     |          |       |  |          |       |  |       |  |       | 
     |          +--+    |  |          +---+   |  |    +--+  +--+    | 
     |             |    |  |              |   |  |    |        |    | 
     |             v    |  |              v   |  |    v        v    | 
     | +----+    +----+ |  | +----+    +----+ |  | +----+    +----+ | 
     | | T1 |<-->| T3 | |  | | T1 |<-->| T3 | |  | | T1 |<-->| T3 | | 
     | +----+    +----+ |  | +----+    +----+ |  | +----+    +----+ | 
     +------------------+  +------------------+  +------------------+ 
     4. T2, T3 oneway      5. T2, T3 bothway     6. T1, T2 bothway  
    
   Note: the direction of the arrow indicates the direction of flow 
    
                     Figure 2[sic]: Example topologies 
    
     
    
     
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     +------------------+  +------------------+  +------------------+ 
     |      +----+      |  |      +----+      |  |      +----+      | 
     |      | T2 |      |  |      | T2 |      |  |      | T2 |      | 
     |      +----+      |  |      +----+      |  |      +----+      | 
     |       ^  ^       |  |       ^  ^       |  |       ^  ^       | 
     |       |  |       |  |       |  |       |  |       |  |       | 
     |    +--+  +--+    |  |    +--+  +---+   |  |    +--+  +--+    | 
     |    |        |    |  |    |         |   |  |    |        |    | 
     |    v        v    |  |    v         v   |  |    v        v    | 
     | +----+  1 +----+ |  | +----+  1 +----+ |  | +----+  1 +----+ | 
     | | T1 |<-->| T3 | |  | | T1 |<-->| T3 | |  | | T1 |<---| T3 | | 
     | |    |<-->|    | |  | |    |--->|    | |  | |    |--->|    | | 
     | +----+  2 +----+ |  | +----+  2 +----+ |  | +----+  2 +----+ | 
     +------------------+  +------------------+  +------------------+ 
     1. No Topology Desc.  2. T1,T3,oneway,2     3. T3,T1,oneway,1 
    
    
    
    
   Topology Description 
   1        No topology descriptors.  When no topology descriptors are 
            included, all terminations have a both way connection to 
            all other terminations. 
   2        T1, T2, Isolate.  Removes the connection between T1 and 
            T2.T3 has a both way connection with both T1 and T2.  T1 
            and T2 have bothway connection to T3. 
   3        T3, T2, oneway.  A oneway connection from T3 to T2 (i.e. T2 
            receives media flow from T3).  A bothway connection between 
            T1 and T3. 
   4        T2, T3, oneway.  A oneway connection between T2 to T3.  T1 
            and T3 remain bothway connected 
   5        T2, T3 bothway.  T2 is bothway connected to T3.  This 
            results in the same as 2. 
   6        T1, T2 bothway (T2, T3 bothway and T1,T3 bothway may be 
            implied or explicit).  All terminations have a bothway 
            connection to all other terminations. 
    
   A oneway connection must implemented in such a way that the other 
   Terminations in the Context are not aware of the change in topology.  
    
7.1.19  Context Attribute Descriptor 
    
   A context attribute descriptor is used to specify properties 
   (defined in packages) that apply to the context as a whole. 
   Termination properties are not valid in the Context Attribute 
   Desciptor. The Context Attribute Descriptor occurs before the 
   commands in an action.  It is possible to have an action containing 
   only a Context Attribute Descriptor, provided that the context to 
   which the action applies already exists. Values of context 
   properties may be underspecified as in section 7.1.1. 
    
   A new setting of the Context Attribute Descriptor completely 
   replaces the previous setting of that descriptor in the MG.  Thus to 
     
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   retain information from the previous setting the MGC must include 
   that information in the new setting.  If the MGC wishes to delete 
   some information from the existing descriptor, it merely resends the 
   descriptor with the unwanted information stripped out. 
    
7.1.20  Error Descriptor 
    
   If a command responder encounters an error when processing a 
   transaction request, it must include an error descriptor in its 
   response.  A Notify request may contain an error descriptor as well. 
    
   An error descriptor consists of an error code, optionally 
   accompanied by an error text.  Section 7.3 contains a list of valid 
   error codes. 
    
   An error descriptor shall be specified at the "deepest level" that 
   is semantically appropriate for the error being described and that 
   is possible given any parsing problems with the original request. An 
   error descriptor may refer to a syntactical construct other than 
   where it appears. For example, error descriptor, 422 “ Syntax Error 
   in Action, could appear within a command even though it refers to 
   the larger construct--the action--and not the particular command 
   within which it appears. 
    
    
7.2     Command Application Programming Interface 
    
   Following is an Application Programming Interface (API) describing 
   the Commands of the protocol.  This API is shown to illustrate the 
   Commands and their parameters and is not intended to specify 
   implementation (e.g. via use of blocking function calls).  It 
   describes the input parameters in parentheses after the command name 
   and the return values in front of the Command. This is only for 
   descriptive purposes; the actual Command syntax and encoding are 
   specified in later subsections.  The order of parameters to commands 
   is not fixed.  Descriptors may appear as parameters to commands in 
   any order.  The descriptors SHALL be processed in the order in which 
   they appear. 
    
   An error descriptor is a possible reply to any command, the API does 
   not specifically show this. 
    
   All parameters enclosed by square brackets ([. . . ]) are considered 
   optional. 
    
7.2.1   Add 
    
   The Add Command adds a Termination to a Context. 
    
   TerminationID 
        [,MediaDescriptor] 
        [,ModemDescriptor] 
        [,MuxDescriptor] 
        [,EventsDescriptor] 
     
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        [,SignalsDescriptor] 
        [,DigitMapDescriptor] 
        [,ObservedEventsDescriptor] 
        [,EventBufferDescriptor] 
        [,StatisticsDescriptor]  
        [,PackagesDescriptor] 
   Add( TerminationID 
        [, MediaDescriptor] 
        [, ModemDescriptor] 
        [, MuxDescriptor] 
        [, EventsDescriptor] 
        [, EventBufferDescriptor] 
        [, SignalsDescriptor] 
        [, DigitMapDescriptor] 
        [, AuditDescriptor] 
   ) 
    
   The TerminationID specifies the termination to be added to the 
   Context.  The Termination is either created, or taken from the null 
   Context. If a CHOOSE wildcard is used in the TermintationID, the  
   selected TerminationID will be returned.  Wildcards may be used in 
   an Add, but such usage would be unusual.  If the wildcard matches 
   more than one TerminationID, all possible matches are attempted, 
   with results reported for each one.  The order of attempts when 
   multiple TerminationIDs match is not specified. 
    
   The optional MediaDescriptor describes all media streams. 
    
   The optional ModemDescriptor and MuxDescriptor specify a modem and 
   multiplexer if applicable. For convenience, if a Multiplex 
   Descriptor is present in an Add command and lists any Terminations 
   that are not currently in the Context, such Terminations are added 
   to the context as if individual Add commands listing the 
   Terminations were invoked.  If an error occurs on such an implied 
   Add, error 471 “ Implied Add for Multiplex failure shall be returned 
   and further processing of the command shall cease. 
    
   The EventsDescriptor parameter is optional.  If present, it provides 
   the list of events that should be detected on the Termination. 
    
   The EventBufferDescriptor parameter is optional.  If present, it 
   provides the list of events that the MG is requested to detect and 
   buffer when EventBufferControl equals LockStep. 
    
   The SignalsDescriptor parameter is optional.  If present, it 
   provides the list of signals that should be applied to the 
   Termination. 
    
   The DigitMapDescriptor parameter is optional.  If present, defines a 
   DigitMap definition that may be used in an EventsDescriptor. 
    
   The AuditDescriptor is optional.  If present, the command will 
   return descriptors as specified in the AuditDescriptor.    
    
     
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   All descriptors that can be modified could be returned by MG if a 
   parameter was underspecified or overspecified.  ObservedEvents, 
   Statistics, and Packages, and the EventBuffer Descriptors are 
   returned only if requested in the AuditDescriptor. 
    
   Add SHALL NOT be used on a Termination with a serviceState of 
   ŸOutofService÷. 
    
7.2.2   Modify 
    
   The Modify Command modifies the properties of a Termination. 
    
   TerminationID 
        [,MediaDescriptor] 
        [,ModemDescriptor] 
        [,MuxDescriptor] 
        [,EventsDescriptor] 
        [,SignalsDescriptor] 
        [,DigitMapDescriptor] 
        [,ObservedEventsDescriptor] 
        [,EventBufferDescriptor] 
        [,StatisticsDescriptor]  
        [,PackagesDescriptor] 
   Modify( TerminationID 
        [, MediaDescriptor] 
        [, ModemDescriptor] 
        [, MuxDescriptor] 
        [, EventsDescriptor] 
        [, EventBufferDescriptor] 
        [, SignalsDescriptor] 
        [, DigitMapDescriptor] 
        [, AuditDescriptor] 
   ) 
    
   The TerminationID may be specific if a single Termination in the 
   Context is to be modified.  Use of wildcards in the TerminationID 
   may be appropriate for some operations. If the wildcard matches more 
   than one TerminationID, all possible matches are attempted, with 
   results reported for each one.  The order of attempts when multiple 
   TerminationIDs match is not specified. The CHOOSE option is an 
   error, as the Modify command may only be used on existing 
   Terminations. 
    
   The remaining parameters to Modify are the same as those to Add.  
   Possible return values are the same as those to Add. 
    
7.2.3   Subtract 
    
   The Subtract Command disconnects a Termination from its Context and 
   returns statistics on the Termination's participation in the 
   Context. 
    
   TerminationID 
        [,MediaDescriptor] 
     
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        [,ModemDescriptor] 
        [,MuxDescriptor] 
        [,EventsDescriptor] 
        [,SignalsDescriptor] 
        [,DigitMapDescriptor] 
        [,ObservedEventsDescriptor] 
        [,EventBufferDescriptor] 
        [,StatisticsDescriptor]  
        [,PackagesDescriptor] 
   Subtract(TerminationID 
        [, AuditDescriptor] 
   ) 
    
   TerminationID in the input parameters represents the Termination 
   that is being subtracted.  The TerminationID may be specific or may 
   be a wildcard value indicating that all (or a set of related) 
   Terminations in the Context of the Subtract Command are to be 
   subtracted. If the wildcard matches more than one TerminationID, all 
   possible matches are attempted, with results reported for each one.  
   The order of attempts when multiple TerminationIDs match is not 
   specified.  
    
   The use of CHOOSE in the TerminationID is an error, as the Subtract 
   command may only be used on existing Terminations.   
    
   ALL may be used as the ContextID as well as the TerminationId in a 
   Subtract, which would have the effect of deleting all contexts, 
   deleting all ephemeral terminations, and returning all physical 
   terminations to Null context. Subtract of termination from the NULL 
   context is not allowed. 
    
   By default, the Statistics parameter is returned to report 
   information collected on the Termination or Terminations specified 
   in the Command.  The information reported applies to the 
   Termination's or Terminations' existence in the Context from which 
   it or they are being subtracted. 
    
   The AuditDescriptor is optional.  If present, the command will 
   return only those descriptors specified in the AuditDescriptor, 
   which may be empty. If omitted, the Statistics descriptor is 
   returned, by default.  Possible return values are the same as those 
   to Add. 
    
   When a provisioned Termination is Subtracted from a context, its 
   property values shall revert to:  
    
   ¹    the default value, if specified for the property and not 
   overridden by provisioning, 
    
   ¹    otherwise, the provisioned value. 
    
     
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7.2.4   Move 
    
   The Move Command moves a Termination to another Context from its 
   current Context in one atomic operation.  The Move command is the 
   only command that refers to a Termination in a Context different 
   from that to which the command is applied.  The Move command shall 
   not be used to move Terminations to or from the null Context. 
    
   TerminationID 
        [,MediaDescriptor] 
        [,ModemDescriptor] 
        [,MuxDescriptor] 
        [,EventsDescriptor] 
        [,SignalsDescriptor] 
        [,DigitMapDescriptor] 
        [,ObservedEventsDescriptor] 
        [,EventBufferDescriptor] 
        [,StatisticsDescriptor]  
        [,PackagesDescriptor] 
   Move( TerminationID 
        [, MediaDescriptor] 
        [, ModemDescriptor] 
        [, MuxDescriptor] 
        [, EventsDescriptor] 
        [, EventBufferDescriptor] 
        [, SignalsDescriptor] 
        [, DigitMapDescriptor] 
        [, AuditDescriptor] 
   ) 
    
   The TerminationID specifies the Termination to be moved.  It may be 
   wildcarded, but CHOOSE shall not be used in the TerminationID.  If 
   the wildcard matches more than one TerminationID, all possible 
   matches are attempted, with results reported for each one.  The 
   order of attempts when multiple TerminationIDs match is not 
   specified. By convention, the Termination is subtracted from its 
   previous Context. The Context to which the Termination is moved is 
   indicated by the target ContextId in the Action.  If the last 
   remaining Termination is moved out of a Context, the Context is 
   deleted. 
    
    The Move command does not affect the properties of the Termination 
   on which it operates, except those properties explicitly modified by 
   descriptors included in the Move command. The AuditDescriptor with 
   the Statistics option, for example, would return statistics on the 
   Termination just prior to the Move.  Possible descriptors returned 
   from Move are the same as for Add. 
    
   Move SHALL NOT be used on a Termination with a serviceState of 
   ŸOutofService÷. 
    
     
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7.2.5   AuditValue 
    
   The AuditValue Command returns the current values of properties, 
   events, signals and statistics associated with Terminations. An 
   AuditValue may be requested for the contents of a descriptor or for 
   a single property, event, signal or statistics. 
    
   TerminationID 
        [,MediaDescriptor] 
        [,ModemDescriptor] 
        [,MuxDescriptor] 
        [,EventsDescriptor] 
        [,SignalsDescriptor] 
        [,DigitMapDescriptor] 
        [,ObservedEventsDescriptor] 
        [,EventBufferDescriptor] 
        [,StatisticsDescriptor]  
        [,PackagesDescriptor] 
   AuditValue(TerminationID, AuditDescriptor) 
    
   TerminationID may be specific or wildcarded. If the wildcard matches 
   more than one TerminationID, all possible matches are attempted, 
   with results reported for each one.  The order of attempts when 
   multiple TerminationIDs match is not specified. If a wildcarded 
   response is requested, only one command return is generated, with 
   the contents containing the union of the values of all Terminations 
   matching the wildcard.  This convention may reduce the volume of 
   data required to audit a group of Terminations.  Use of CHOOSE is an 
   error. 
    
   Descriptors or individual properties, signals, events and statistics 
   can be audited. 
    
   ¹    An audit of a descriptor may be requested by providing the 
   appropriate descriptor to be audited.  
    
   ¹    To audit an individual property in the media descriptor the 
   relevant stream ID (optional), group ID(optional) and propertyID is
   included. The current value of the property is returned. Group ID is 
   used in the case where the local control Reserve Group flag is used. 
   Group ID 1 corresponds to the first group reserved, Group ID 2 the 
   next group etcetera. 
    
   ¹    To audit a signal the relevant signal list ID and/or signal ID 
   is provided. Only if the signal is active the values of all the 
   signal parameters are returned including:the keepactive indication, 
   signal type, duration, signal completion indication and package 
   defined properties. 
    
   ¹    To audit an event or event in the active event buffer, the 
   relevant stream id (optional), eventID, requestID (optional) is 
   provided. The values of all the event parameters are returned 
   including: event actions and packaged defined parameters. 
    
     
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   ¹    To audit a statistic the identity of statistic is provided. The 
   current value of the statistic is returned. The statistic is not 
   reset. 
    
   ¹    To audit a modem the identity of the modem is provided. The 
   modem parameter values are then returned. 
    
   ¹    To audit a package the identity and version of the package is 
   provided. All properties, signals, events and statistics defined in 
   that particular package are returned with their current value. 
    
   It is possible to audit multiple individual items in one request. 
    
   If a descriptor audit is requested the appropriate descriptors, with 
   the current values for the Termination, are returned from 
   AuditValue.  Values appearing in multiple instances of a descriptor 
   are defined to be alternate values supported, with each parameter in 
   a descriptor considered independent. 
    
   ObservedEvents returns a list of events in the EventBuffer. If the 
   ObservedEventsDescriptor is audited while a DigitMap is active, the 
   returned ObservedEvents descriptor also includes a digit map 
   completion event that shows the current dial string but does not 
   show a termination method. 
    
   EventBuffer returns the set of events and associated parameter 
   values currently enabled in the EventBufferDescriptor.   
   PackagesDescriptor returns a list of packages realized by the 
   Termination.  DigitMapDescriptor returns the name or value of the 
   current DigitMap for the Termination.  DigitMap requested in an 
   AuditValue command with TerminationID ALL returns all DigitMaps in 
   the gateway.  Statistics returns the current values of all 
   statistics being kept on the Termination.  Specifying an empty Audit 
   Descriptor results in only the TerminationID being returned.  This 
   may be useful to get a list of TerminationIDs when used with 
   wildcard.  Annexes A and B provide a special syntax for presenting 
   such a list in condensed form, such that the AuditValue command tag 
   does not have to be repeated for each TerminationID. 
    
   AuditValue results depend on the Context, viz. specific, null, or 
   wildcarded.  (Note that ContextID All does not include the null 
   Context. )  The TerminationID may be specific, or wildcarded.  
    
   The following are examples of what is returned in case the context 
   and/or the termination is wildcarded and a wildcarded response has 
   been specified: 
    
   Assume the gateway has 4 terminations : t1/1, t1/2, t2/1 and t2/2 
    
   Assume terminations t1/* have implemented packages aaa and bbb and 
   terminations t2/* have implemented packages ccc and ddd. 
    
   Assume context 1 has t1/1 and t2/1 in it, and context 2 has t1/2 and 
   t2/2 in it. 
     
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   The command: 
        Context=1{Audit=t1/1{Audit{Packages}} 
   Returns:  
        Context=1{Audit=t1/1{Packages{aaa,bbb}}}} 
    
   The command:  
        Context=*{Audit=t2/*{Audit{Packages}}  
   Returns: 
        Context=1{Audit=t2/1{Packages{ccc,ddd}}}, 
        Context=2{Audit=t2/2{Packages{ccc,ddd}}}  
    
   The command: 
        Context=*{W-Audit=t1/*{Audit{Packages}}  
   Returns: 
        Context=*{W-Audit=t1/*{Packages{aaa,bbb}}  
    
   Note: A wildcard response may also be used for other commands such 
   as Subtract. 
    
   The following illustrates other information that can be obtained 
   with the Audit Command: 
    
   ContextID TerminationID    Information Obtained 
   Specific  wildcard         Audit of matching Terminations in a 
                               Context 
   Specific  specific         Audit of a single Termination in a 
                               Context 
   Null      Root             Audit of Media Gateway state and events 
   Null      wildcard         Audit of all matching Terminations in 
                               the Null Context 
   Null      specific         Audit of a single Termination outside of 
                               any Context 
   All       wildcard         Audit of all matching Terminations and 
                               the Context to which they are associated 
   All       Root             List of all ContextIds (the list of 
                               ContextIds should be returned by using 
                               multiple Action Replys, each containing 
                               a ContextId from the list) 
   All       Specific         (Non-null) Context Id in which the 
                               Termination currently exists 
    
 
7.2.6   AuditCapabilities 
    
   The AuditCapabilities Command returns the possible values of 
   properties, events, signals and statistics associated with 
   Terminations. An AuditCapabilities may be requested for the contents 
   of a descriptor or for a single property, event, signal or 
   statistics. 
    
   TerminationID 
        [,MediaDescriptor] 
     
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        [,ModemDescriptor] 
        [,MuxDescriptor] 
        [,EventsDescriptor] 
        [,SignalsDescriptor] 
        [,ObservedEventsDescriptor] 
        [,EventBufferDescriptor] 
        [,StatisticsDescriptor]  
   AuditCapabilities(TerminationID, AuditDescriptor) 
    
   Descriptors or individual properties, signals, events and statistics 
   can be audited. 
    
   ¹    An audit of a descriptor may be requested by providing the 
   appropriate descriptor to be audited.  
    
   ¹    To audit an individual property in the media descriptor the 
   relevant stream ID (optional) and propertyID is included. A list of 
   possible values of the property are returned.  
    
   ¹    To audit a signal the relevant signal list ID and/or signal ID 
   is provided. A list of possible values associated with each signal 
   parameter is returned (including: the keepactive indication, signal 
   type, duration, signal completion indication and package defined 
   properties). 
    
   ¹    To audit an event or event in the event buffer the relevant 
   stream id (optional), eventID, requestID (optional) is provided. A 
   list of possible values associated with each event parameter is 
   returned (including: event actions and packaged defined parameters). 
    
   ¹    To audit a statistic the identity of statistic is provided. The 
   possible values of the statistic are returned. The statistic is not 
   reset. 
    
   ¹    To audit a modem the identity of the modem is provided. The 
   possible values of the modem parameter values are then returned. 
    
   If a descriptor audit is requested the appropriate descriptors, with 
   the possible values for the Termination are returned from 
   AuditCapabilities.  Descriptors may be repeated where there are 
   multiple possible values. 
    
   If a wildcarded response is requested, only one command return is 
   generated, with the contents containing the union of the values of 
   all Terminations matching the wildcard.  This convention may reduce 
   the volume of data required to audit a group of Terminations. 
   Interpretation of what capabilities are requested for various values 
   of ContextID and TerminationID is the same as in AuditValue. 
    
   The EventsDescriptor returns the list of possible events on the 
   Termination together with the list of all possible values for the 
   EventsDescriptor Parameters.  EventBufferDescriptor returns the same 
   information as EventsDescriptor.  The SignalsDescriptor returns the 
   list of possible signals that could be applied to the Termination 
     
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   together with the list of all possible values for the Signals 
   Parameters.  StatisticsDescriptor returns the names of the 
   statistics being kept on the termination.  ObservedEventsDescriptor 
   returns the names of active events on the termination.  DigitMap and 
   Packages are not legal in AuditCapability. 
    
   If a property, signal, event or statistic is audited the appropriate 
   properties, signals events and statistics with the capabilities of 
   the Termination, are returned from AuditValue. 
    
7.2.7   Notify 
    
   The Notify Command allows the Media Gateway to notify the Media 
   Gateway Controller of events occurring within the Media Gateway. 
    
   TerminationID 
   Notify(TerminationID, ObservedEventsDescriptor, 
   [ErrorDescriptor]) 
    
   The TerminationID parameter specifies the Termination issuing the 
   Notify Command.  The TerminationID shall be a fully qualified name. 
    
   The ObservedEventsDescriptor contains the RequestID and a list of 
   events that the Media Gateway detected in the order that they were 
   detected. Each event in the list is accompanied by parameters 
   associated with the event and optionally an indication of the time 
   that the event was detected.  Procedures for sending Notify commands 
   with RequestID equal to 0 are for further study.   
    
    Notify Commands with RequestID not equal to 0 shall occur only as 
   the result of detection of an event specified by an Events 
   Descriptor which is active on the termination concerned. 
    
   The RequestID returns the RequestID parameter of the 
   EventsDescriptor that triggered the Notify Command.  It is used to 
   correlate the notification with the request that triggered it.  The 
   events in the list must have been requested via the triggering 
   EventsDescriptor or embedded events descriptor unless the RequestID 
   is 0 (which is for further study). 
    
   The ErrorDescriptor may be sent in the Notify as a result of Error 
   518 - Event buffer full. 
    
7.2.8   ServiceChange 
    
   The ServiceChange Command allows the Media Gateway to notify the 
   Media Gateway Controller that a Termination or group of Terminations 
   is about to be taken out of service or has just been returned to 
   service.   The Media Gateway Controller may indicate that 
   Termination(s) shall be taken out of or returned to service.  The 
   Media Gateway may notify the MGC that the capability of a 
   Termination has changed.  It also allows a MGC to hand over control 
   of a MG to another MGC. 
    
     
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   TerminationID, 
        [ServiceChangeDescriptor] 
   ServiceChange(TerminationID, ServiceChangeDescriptor) 
    
   The TerminationID parameter specifies the Termination(s) that are 
   taken out of or returned to service.  Wildcarding of Termination 
   names is permitted, with the exception that the CHOOSE mechanism 
   shall not be used.  Use of the "Root" TerminationID indicates a 
   ServiceChange affecting the entire Media Gateway. 
    
   The ServiceChangeDescriptor contains the following parameters as 
   required: 
   ¦    ServiceChangeMethod  
   ¦    ServiceChangeReason  
   ¦    ServiceChangeDelay  
   ¦    ServiceChangeAddress 
   ¦    ServiceChangeProfile 
   ¦    ServiceChangeVersion 
   ¦    ServiceChangeMgcId 
   ¦    TimeStamp 
   ¦    ServiceChangeInfo 
    
   The ServiceChangeMethod parameter specifies the type of 
   ServiceChange that will or has occurred: 
    
   1)   Graceful “ indicates that the specified Terminations will be 
   taken out of service after the specified ServiceChangeDelay; 
   established connections are not yet affected, but the Media Gateway 
   Controller should refrain from establishing new connections and 
   should attempt to gracefully tear down existing connections on the 
   Termination(s) affected by the serviceChange command. The MG should 
   set termination serviceState at the expiry of ServiceChangeDelay or 
   the removal of the termination from an active context (whichever is 
   first), to "out of service". 
    
   2)   Forced “ indicates that the specified Terminations were taken 
   abruptly out of service and any established connections associated 
   with them may be lost. For non-Root terminations the MGC is 
   responsible for cleaning up the context (if any) with which the 
   failed termination is associated.  At a minimum the termination 
   shall be subtracted from the context.  The termination serviceState 
   should be "out of service". For the root termination the MGC can 
   assume that all connections are lost on the MG and thus can consider 
   that all the terminations have been subtracted. 
    
   3)   Restart “ indicates that service will be restored on the 
   specified Terminations after expiration of the ServiceChangeDelay. 
   The serviceState should be set  to "inService" upon expiry of 
   ServiceChangeDelay.   
    
   4)   Disconnected “ always applied with the Root TerminationID, 
   indicates that the MG lost communication with the MGC, but it was 
   subsequently restored to the same MGC (possibly after trying other 
   MGCs on pre-provisioned list).  Since MG state may have changed, the 
     
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   MGC may wish to use the Audit command to resynchronize its state 
   with the MG's. 
    
   5)   Handoff “ sent from the MGC to the MG, this reason indicates 
   that the MGC is going out of service and a new MGC association must 
   be established. Sent from the MG to the MGC, this indicates that the 
   MG is attempting to establish a new association in accordance with a 
   Handoff received from the MGC with which it was previously 
   associated. 
    
   6)   Failover “ sent from MG to MGC to indicate the primary MG is 
   out of service and a secondary MG is taking over. This serviceChange 
   method is also sent from the MG to the MGC when the MG detects that 
   MGC has failed. 
    
   7)   Another value whose meaning is mutually understood between the 
   MG and the MGC. 
    
   The ServiceChangeReason parameter specifies the reason why the 
   ServiceChange has or will occur.  It consists of an alphanumeric 
   token (IANA registered) and, optionally, an explanatory string. 
    
   The optional ServiceChangeAddress parameter specifies the address 
   (e.g., IP port number for IP networks) to be used for subsequent 
   communications.  It can be specified in the input parameter 
   descriptor or the returned result descriptor.  ServiceChangeAddress 
   and ServiceChangeMgcId parameters must not both be present in the 
   ServiceChangeDescriptor or the ServiceChangeResultDescriptor.  The 
   ServiceChangeAddress provides an address to be used within the 
   context of the association currently being negotiated, while the 
   ServiceChangeMgcId provides an alternate address where the MG should 
   seek to establish another association. Note that the use of 
   ServiceChangeAddress is not encouraged.  MGCs and MGs must be able 
   to cope with the ServiceChangeAddress being either a full address or 
   just a port number in the case of TCP transports. 
    
   The optional ServiceChangeDelay parameter is expressed in seconds.  
   If the delay is absent or set to zero, the delay value should be 
   considered to be null.  In the case of a "graceful" 
   ServiceChangeMethod, a null delay indicates that the Media Gateway 
   Controller should wait for the natural removal of existing 
   connections and should not establish new connections.  For 
   "graceful" only, a null delay means the MG must not set serviceState 
   "out of service" until the termination is in the null context. 
    
   The optional ServiceChangeProfile parameter specifies the Profile 
   (if any) of the protocol supported.  The ServiceChangeProfile 
   includes the version of the profile supported. 
    
   The optional ServiceChangeVersion parameter contains the protocol 
   version and is used if protocol version negotiation occurs (see 
   section 11.3). 
    
     
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   The optional TimeStamp parameter specifies the actual time as kept 
   by the sender.  As such, it is not necessarily absolute time 
   according to, for example, a local time zone·it merely establishes 
   an arbitrary starting time against which all future timestamps 
   transmitted by a sender during this association shall be compared.  
   It can be used by the responder to determine how its notion of time 
   differs from that of its correspondent.  TimeStamp is sent with a 
   precision of hundredths of a second, and is expressed in UTC.  
    
   The optional Extension parameter may contain any value whose meaning 
   is mutually understood by the MG and MGC. 
    
   The optional ServiceChangeInfo parameter may contain the 
   package/property/signal/event/statistic of the reason that caused 
   the service change. 
    
   A ServiceChange Command specifying the "Root" for the TerminationID 
   and ServiceChangeMethod equal to Restart is a registration command 
   by which a Media Gateway announces its existence to the Media 
   Gateway Controller. The Media Gateway may also announce a 
   registration command by specifying the "Root" for the TerminationID 
   and ServiceChangeMethod equal to Failover when the MG detects MGC 
   failures.  The Media Gateway is expected to be provisioned with the 
   name of one primary and optionally some number of alternate Media 
   Gateway Controllers.    Acknowledgement of the ServiceChange Command 
   completes the registration process, except when the MGC has returned 
   an alternative ServiceChangeMgcId as described in the following 
   paragraph.  The MG may specify the transport ServiceChangeAddress to 
   be used by the MGC for sending messages in the ServiceChangeAddress 
   parameter in the input ServiceChangeDescriptor. The MG may specify 
   an address in the ServiceChangeAddress parameter of the 
   ServiceChange request, and the MGC may also do so in the 
   ServiceChange reply.  In either case, the recipient must use the 
   supplied address as the destination for all subsequent transaction 
   requests within the association.  At the same time, as indicated in 
   section 9, transaction replies and pending indications must be sent 
   to the address from which the corresponding requests originated.  
   This must be done even if it implies extra messaging because 
   commands and responses cannot be packed together.  The TimeStamp 
   parameter shall be sent with a registration command and its 
   response. 
    
   The Media Gateway Controller may return an ServiceChangeMgcId 
   parameter that describes the Media Gateway Controller that should 
   preferably be contacted for further service by the Media Gateway.  
   In this case the Media Gateway shall reissue the ServiceChange 
   command to the new Media Gateway Controller.   The MGC specified in 
   an ServiceChangeMgcId, if provided, shall be contacted before any 
   further alternate MGCs.  On a HandOff message from MGC to MG, the 
   ServiceChangeMgcId is the new MGC that will take over from the 
   current MGC. 
    
     
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   The return from ServiceChange is empty except when the Root 
   terminationID is used.  In that case it includes the following 
   parameters as required: 
    
   ¹    ServiceChangeAddress, if the responding MGC wishes to specify a 
   new destination for messages from the MG for the remainder of the 
   association; 
    
   ¹    ServiceChangeMgcId, if the responding MGC does not wish to 
   sustain an association with the MG; 
    
   ¹    ServiceChangeProfile, if the responder wishes to negotiate the 
   profile to be used for the association. The profile (name and 
   version) is only returned in reply the case that the MGC cannot 
   support the specified profiles in the ServiceChangeRequest. The 
   returned shall indicate the profile and version supported or 
   "NoProfile" if no profile is supported. Upon reception of a profile 
   in the reply the MG may continue the relationship with the current 
   MGC or contact secondary MGCs and establish a relationship with 
   them. If the profile is not returned the MGC will use the 
   capabilities specified by the Profile indicated in the service 
   change request. 
    
   ¹    ServiceChangeVersion, if the responder wishes to negotiate the 
   version of the protocol to be used for the association. 
    
   The following ServiceChangeReasons are defined.  This list may be 
   extended by an IANA registration as outlined in section 14.3. 
    
        900 Service Restored 
        901 Cold Boot 
        902 Warm Boot 
        903 MGC Directed Change 
        904 Termination malfunctioning 
        905 Termination taken out of service 
        906 Loss of lower layer connectivity (e.g. downstream sync) 
        907 Transmission Failure 
        908 MG Impending Failure 
        909 MGC Impending Failure 
        910 Media Capability Failure 
        911 Modem Capability Failure 
        912 Mux Capability Failure 
        913 Signal Capability Failure 
        914 Event Capability Failure 
        915 State Loss 
        916 Packages Change 
        917 Capability Change 
    
7.2.9   Manipulating and Auditing Context Attributes 
    
   The commands of the protocol as discussed in the preceding sections 
   apply to terminations.  This section specifies how contexts are 
   manipulated and audited. 
    
     
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   Commands are grouped into actions (see section 8).  An action 
   applies to one context.  In addition to commands, an action may 
   contain context manipulation and auditing instructions. 
    
   An action request sent to a MG may include a request to audit 
   attributes of a context. There are three types of audit: 
    
   Value Audit: the MGC may audit a specific Context to determine the 
   current value of the ContextAttribute Descriptor or individual 
   context properties.  The MGC may determine the current values for 
   all existing (non-NULL) Contexts by specifying ContextID ALL in the 
   Audit request. If context properties are added or have been modified 
   by the same action as the Audit Value request the value/s returned 
   shall be after the action has been applied 
    
   Capabilities Audit: the MGC may audit a specific Context to 
   determine the possible values that the ContextAttribute Descriptor 
   or individual context properties can assume.  The MGC may determine 
   the possible values for the entire MG by specifying ContextID ALL in 
   the audit request. 
    
   Packages Audit: the MGC may audit a specific Context to determine 
   which Packages realise the context properties for that Context.  The 
   MGC may determine all packages that can realise context properties 
   for the entire MG by specifying ContextID ALL in the audit request. 
    
   The following illustrates information that can be obtained with a 
   context Audits: 
    
   ContextID TerminationID Audit           Audit         Audit Package 
                                            Capability 
                                             
   Specific  Not           Context         Context       Packages that 
             Applicable    attribute's     attribute's   may be used 
                            value in the    possible      in the 
                            specified       values in the specified 
                            context.        specified     context to 
                                            context.      realise the 
                                                          Context 
                                                          attributes. 
                                                           
   Null      Not           Not Allowed     Not Allowed   Not Allowed 
             Applicable 
              
   All       Not           Current values  A response    A response 
             Applicable    for all         for ContextID for ContextID 
                            existing (non-  ALL is        ALL is 
                            NULL) Contexts  returned with returned with 
                            by specifying   context       all packages 
                            ContextID ALL   attribute's   in the MG 
                            in the Audit    possible      that contain 
                            request. A      values across context 
                            response for    the entire    attributes. 
     
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                            ContextID ALL   MG. 
                            is returned 
                            with the union 
                            of the values. 
    
      
   An action may also include a request to change the attributes of a 
   context. 
    
   The context properties that may be included in an action reply are 
   used to return information to a MGC.  This can be information 
   requested by an audit of context attributes or details of the effect 
   of manipulation of a context. 
    
   If a MG receives an action which contains both a request to audit 
   context attributes and a request to manipulate those attributes, the 
   response SHALL include the values of the attributes after processing 
   the manipulation request. 
    
7.2.10   Generic Command Syntax 
    
   The protocol can be encoded in a binary format or in a text format.  
   MGCs should support both encoding formats.  MGs may support both 
   formats. 
    
   The protocol syntax for the binary format of the protocol is defined 
   in Annex A.  Annex C specifies the encoding of the Local and Remote 
   descriptors for use with the binary format. 
    
   A complete ABNF of the text encoding of the protocol per RFC2234 is 
   given in Annex B.  SDP is used as the encoding of the Local and 
   Remote Descriptors for use with the text encoding as modified in 
   section 7.1.8. 
    
    
7.3     Command Error Codes 
    
   Errors consist of an IANA registered error code and an explanatory 
   string.  Sending the explanatory string is optional.  
   Implementations are encouraged to append diagnostic information to 
   the end of the string. 
    
   When a MG reports an error to a MGC, it does so in an error 
   descriptor.  An error descriptor consists of an error code and 
   optionally the associated explanatory string. 
    
   H.248 Annex L contains the error codes supported by H.248. 
    
    
8.      TRANSACTIONS 
    
   Commands between the Media Gateway Controller and the Media Gateway 
   are grouped into Transactions, each of which is identified by a 
     
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   TransactionID.  Transactions consist of one or more Actions.  An 
   Action consists of a non-empty series of Commands that are limited 
   to operating within a single Context.   Consequently each Action 
   typically specifies a ContextID.  However, there are two 
   circumstances where a specific ContextID is not provided with an 
   Action.  One is the case of modification of a Termination outside of 
   a Context.  The other is where the controller requests the gateway 
   to create a new Context.  Following is a graphic representation of 
   the Transaction, Action and Command relationships. 
    
      +----------------------------------------------------------+ 
      | Transaction x                                            | 
      |  +----------------------------------------------------+  | 
      |  | Action 1                                           |  | 
      |  | +---------+  +---------+  +---------+  +---------+ |  | 
      |  | | Command |  | Command |  | Command |  | Command | |  | 
      |  | |    1    |  |    2    |  |    3    |  |    4    | |  | 
      |  | +---------+  +---------+  +---------+  +---------+ |  | 
      |  +----------------------------------------------------+  | 
      |                                                          | 
      |  +----------------------------------------------------+  | 
      |  | Action 2                                           |  | 
      |  | +---------+                                        |  | 
      |  | | Command |                                        |  | 
      |  | |    1    |                                        |  | 
      |  | +---------+                                        |  | 
      |  +----------------------------------------------------+  | 
      |                                                          | 
      |  +----------------------------------------------------+  | 
      |  | Action 3                                           |  | 
      |  | +---------+  +---------+  +---------+              |  | 
      |  | | Command |  | Command |  | Command |              |  | 
      |  | |    1    |  |    2    |  |    3    |              |  | 
      |  | +---------+  +---------+  +---------+              |  | 
      |  +----------------------------------------------------+  | 
      +----------------------------------------------------------+ 
     
               Figure 5: Transactions, Actions and Commands 
    
   Transactions are presented as TransactionRequests.  Corresponding 
   responses to a TransactionRequest are received in a single reply, 
   possibly preceded by a number of TransactionPending messages (see 
   section 8.2.3).  
     
   Transactions guarantee ordered Command processing.  That is, 
   Commands within a Transaction are executed sequentially. Ordering of 
   Transactions is NOT guaranteed “ transactions may be executed in any 
   order, or simultaneously. 
    
   At the first failing Command in a Transaction, processing of the 
   remaining Commands in that Transaction stops.  If a command contains 
   a wildcarded TerminationID, the command is attempted with each of 
   the actual TerminationIDs matching the wildcard.  A response within 
   the TransactionReply is included for each matching TerminationID, 
     
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   even if one or more instances generated an error.  If any 
   TerminationID matching a wildcard results in an error when executed, 
   any commands following the wildcarded command are not attempted. 
    
   Commands may be marked as "Optional" which can override this 
   behaviour “  if a command marked as Optional results in an error, 
   subsequent commands in the Transaction will be executed.  If a 
   command fails, the MG shall as far as possible restore the state 
   that existed prior to the attempted execution of the command before 
   continuing with command processing. 
    
   A TransactionReply includes the results for all of the Commands in 
   the corresponding TransactionRequest.  The TransactionReply includes 
   the return values for the Commands that were executed successfully, 
   and the Command and error descriptor for any Command that failed.  
   TransactionPending is used to periodically notify the receiver that 
   a Transaction has not completed yet, but is actively being 
   processed.  
    
   Applications SHOULD implement an application level timer per 
   transaction.  Expiration of the timer should cause a retransmission 
   of the request.  Receipt of a Reply should cancel the timer.  
   Receipt of Pending should restart the timer. 
    
8.1     Common Parameters 
    
8.1.1   Transaction Identifiers 
    
   Transactions are identified by a TransactionID, which is assigned by 
   sender and is unique within the scope of the sender.  A response 
   containing an error descriptor to indicate that the TransactionID is 
   missing in a request shall use TransactionID 0 in the corresponding 
   TransactionReply. 
    
8.1.2   Context Identifiers 
    
   Contexts are identified by a ContextID, which is assigned by the 
   Media Gateway and is unique within the scope of the Media Gateway.  
   The Media Gateway Controller shall use the ContextID supplied by the 
   Media Gateway in all subsequent Transactions relating to that 
   Context.  The protocol makes reference to a distinguished value that 
   may be used by the Media Gateway Controller when referring to a 
   Termination that is currently not associated with a Context, namely 
   the null ContextID. 
    
   The CHOOSE wildcard is used to request that the Media Gateway create 
   a new Context.  The MGC shall not use partially specified ContextIDs 
   containing the CHOOSE wildcard. 
    
   The MGC may use the ALL wildcard to address all Contexts on the MG.  
   The null Context is not included when the ALL wildcard is used. 
    
     
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8.2     Transaction Application Programming Interface 
    
   Following is an Application Programming Interface (API) describing 
   the Transactions of the protocol.  This API is shown to illustrate 
   the Transactions and their parameters and is not intended to specify 
   implementation (e.g. via use of blocking function calls).  It will 
   describe the input parameters and return values expected to be used 
   by the various Transactions of the protocol from a very high level.  
   Transaction syntax and encodings are specified in later subsections. 
    
8.2.1   TransactionRequest 
    
   The TransactionRequest is invoked by the sender.  There is one 
   Transaction per request invocation.  A request contains one or more 
   Actions, each of which specifies its target Context and one or more 
   Commands per Context. 
    
   TransactionRequest(TransactionId { 
          ContextID {Command € Command},  
                        . . . 
          ContextID  {Command € Command } }) 
    
   The TransactionID parameter must specify a value for later 
   correlation with the TransactionReply or TransactionPending response 
   from the receiver.  
    
   The ContextID parameter must specify a value to pertain to all 
   Commands that follow up to either the next specification of a 
   ContextID parameter or the end of the TransactionRequest, whichever 
   comes first.  
    
   The Command parameter represents one of the Commands mentioned in 
   the "Command Details" subsection titled "Application Programming 
   Interface". 
    
8.2.2   TransactionReply 
    
   The TransactionReply is invoked by the receiver.  There is one reply 
   invocation per transaction.  A reply contains one or more Actions, 
   each of which must specify its target Context and one or more 
   Responses per Context. The TransactionReply is invoked by the 
   command responder when it has processed the TransactionRequest. 
    
   A TransactionRequest has been processed 
    
   ¹    when all commands in that TransactionRequest have been 
   processed, or 
    
   ¹    when an error is encountered in processing a non-optional 
   command in that TransactionRequest. 
    
   A command has been processed when all descriptors in that command 
   have been processed. 
    
     
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   A SignalsDescriptor is considered to have been processed when it has 
   been established that the descriptor is syntactically valid, the 
   requested signals are supported and they have been queued to be 
   played out. 
    
   An EventsDescriptor or EventBufferDescriptor is considered to have 
   been processed when it has been established that the descriptor is 
   syntactically valid, the requested events can be observed, any 
   embedded signals can be generated, any embedded events can be 
   detected, and the MG has been brought in a state in which the events 
   will be detected.  
     
   TransactionReply(TransactionID { 
        ContextID { Response € Response }, 
        . . . 
        ContextID { Response € Response } }) 
    
   The TransactionID parameter must be the same as that of the 
   corresponding TransactionRequest. 
    
   The ContextID parameter must specify a value to pertain to all 
   Responses for the action.  The ContextID may be specific, all or 
   null.  
    
   Each of the Response parameters represents a return value as 
   mentioned in section 7.2, or an error descriptor if the command 
   execution encountered an error. Commands after the point of failure 
   are not processed and, therefore, Responses are not issued for them.  
    
   An exception to this occurs if a command has been marked as optional 
   in the Transaction request. If the optional command  generates an 
   error, the transaction still continues to execute, so the Reply 
   would, in this case, have Responses after an Error. 
    
   If the receiver encounters an error in processing a ContextID, the 
   requested Action response will consist of the context ID and a 
   single error descriptor, 422 Syntax Error in Action. 
    
   If the receiver encounters an error such that it cannot determine a 
   legal Action, it will return a TransactionReply consisting of the 
   TransactionID and a single error descriptor, 422 Syntax Error in 
   Action. If the end of an action cannot be reliably determined but 
   one or more Commands can be parsed, it will process them and then 
   send 422 Syntax Error in Action as the last action for the 
   transaction.  If the receiver encounters an error such that is 
   cannot determine a legal Transaction, it will return a 
   TransactionReply with a null TransactionID and a single error 
   descriptor (403 Syntax Error in Transaction). 
     
   If the end of a transaction can not be reliably determined and one 
   or more Actions can be parsed, it will process them and then return 
   403 Syntax Error in Transaction as the last action reply for the 
   transaction.  If no Actions can be parsed, it will return 403 Syntax 
   Error in Transaction as the only reply 
     
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   If the terminationID cannot be reliably determined it will send 442 
   Syntax Error in Command as the action reply. 
    
   If the end of a command cannot be reliably determined it will return 
   442 Syntax Error in Command as the reply to the last action it can 
   parse. 
    
8.2.3   TransactionPending 
    
   The receiver invokes the TransactionPending.  A TransactionPending 
   indicates that the Transaction is actively being processed, but has 
   not been completed.  It is used to prevent the sender from assuming 
   the TransactionRequest was lost where the Transaction will take some 
   time to complete. 
    
   TransactionPending(TransactionID { } ) 
    
   The TransactionID parameter must be the same as that of the 
   corresponding TransactionRequest.  A property of root 
   (normalMGExecutionTime) is settable by the MGC to indicate the 
   interval within which the MGC expects a response to any transaction 
   from the MG.  Another property (normalMGCExecutionTime) is settable 
   by the MGC to indicate the interval within which the MG should 
   expect a response to any transaction from the MGC.  Senders may 
   receive more than one TransactionPending for a command.  If a 
   duplicate request is received when pending, the responder may send a 
   duplicate pending immediately, or continue waiting for its timer to 
   trigger another Transaction Pending. 
    
   A property of the root termination (MGOriginatedPendingLimit) is 
   settable by the MGC to indicate the number of TransactionPendings 
   that can be received from the MG. When the value expressed by this 
   property is exceeded, the MG has to stop the transaction processing 
   and send back a TransactionReply otherwise the MGC can assume the 
   Transaction to be in error. 
    
   Another property of the root termination (MGCOriginatedPendingLimit) 
   is settable by the MGC to indicate the number of TransactionPendings 
   that can be received from the MGC. When the value expressed by this 
   property is exceeded, the MGC has to stop the transaction processing 
   and send back a TransactionReply otherwise the MG can assume the 
   Transaction to be in error. 
    
   The xxxOriginatedPendingLimit (MGOriginatedPendingLimit or 
   MGCOriginatedPendingLimit) may be exceeded either because of long 
   command processing or due to an error (e.g. a command caused a 
   loop). In both cases the receiver of the original TransactionRequest 
   will issue a TransactionReply with an error descriptor as a response 
   parameter in correspondence with either the offending long command 
   or the command that caused the error. Further commands in the 
   transaction shall not be processed. Error 5xx  Number of 
   TransactionPendings Exceeded shall be used. 
    
     
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   Note-To prevent a situation where the xxxOriginatedPendingLimit 
   (MGOriginatedPendingLimit or MGCOriginatedPendingLimit) is exceeded 
   due to an error and the receiver of the original TransactionRequest 
   keeps sending TransactionPending, the receiver of the original 
   TransactionRequest should implement a management protection 
   mechanism in order to trigger the appropriate recovery actions. The 
   sender of the original TransactionRequest may keep track of the 
   number of received Pendings and initiate corrective actions 
    
8.3     Messages 
    
   Multiple Transactions can be concatenated into a Message.  Messages 
   have a header, which includes the identity of the sender. The 
   Message Identifier (MID) of a message is set to a provisioned name 
   (e.g. domain address/domain name/device name) of the entity 
   transmitting the message.  Domain name is a suggested default. An 
   H.248 entity (MG/MGC) must consistently use the same MID in all 
   messages it originates for the duration of control association with 
   the peer (MGC/MG). 
    
   Every Message contains a Version Number identifying the version of 
   the protocol the message conforms to.  Versions consist of one or 
   two digits, beginning with version 1 for the present version of the 
   protocol. 
    
   The transactions in a message are treated independently.  There is 
   no order implied, there is no application or protocol 
   acknowledgement of a message. A message is essentially a transport 
   mechanism.  For example, message X containing transaction requests 
   A, B, and C may be responded to with message Y containing replies to 
   A and C and message Z containing the reply to B. Likewise, message L 
   containing request D and message M containing request E may be 
   responded to with message  N containing replies to both D and E.  
    
    
9.      TRANSPORT 
    
   The transport mechanism for the protocol should allow the reliable 
   transport of transactions between an MGC and MG. The transport shall 
   remain independent of what particular commands are being sent and 
   shall be applicable to all application states.  There are several 
   transports defined for the protocol, which are defined in normative 
   Annexes to this document.  Additional Transports may be defined as 
   additional annexes in subsequent editions of this document, or in 
   separate documents.  For transport of the protocol over IP, MGCs 
   shall implement both TCP and UDP/ALF, an MG shall implement TCP or 
   UDP/ALF or both. 
    
   The MG is provisioned with a name or address (such as DNS name or IP 
   address) of a primary and zero or more secondary MGCs (see section 
   7.2.8) that is the address the MG uses to send messages to the MGC. 
   If TCP or UDP is used as the protocol transport and the port to 
   which the initial ServiceChange request is to be sent is not 
   otherwise known, that request should be sent to the default port 
     
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   number for the protocol.  This port number is 2944 for text-encoded 
   operation or 2945 for binary-encoded operation, for either UDP or 
   TCP.  The MGC receives the message containing the ServiceChange 
   request from the MG and can determine the MG's address from it.  As 
   described in section 7.2.8, either the MG or the MGC may supply an 
   address in the ServiceChangeAddress parameter to which subsequent 
   transaction requests must be addressed, but responses (including the 
   response to the initial ServiceChange request) must always be sent 
   back to the address which was the source of the corresponding 
   request. For example: in IP networks, this is the source address in 
   the IP header and the source port number in the TCP/UDP/STCP header. 
    
9.1     Ordering of Commands 
    
   This document does not mandate that the underlying transport 
   protocol guarantees the sequencing of transactions sent to an 
   entity.  This property tends to maximize the timeliness of actions, 
   but it has a few drawbacks.  For example: 
    
   ¦    Notify commands may be delayed and arrive at the MGC after the 
   transmission of a new command changing the EventsDescriptor 
    
   ¦    If a new command is transmitted before a previous one is 
   acknowledged, there is no guarantee that prior command will be 
   executed before the new one. 
    
   Media Gateway Controllers that want to guarantee consistent 
   operation of the Media Gateway may use the following rules.  These 
   rules are with respect to commands that are in different 
   transactions.  Commands that are in the same transaction are 
   executed in order (see section 8). 
    
   1.   When a Media Gateway handles several Terminations, commands 
   pertaining to the different Terminations may be sent in parallel, 
   for example following a model where each Termination (or group of 
   Terminations) is controlled by its own process or its own thread. 
    
   2.   On a Termination, there should normally be at most one 
   outstanding command (Add or Modify or Move), unless the outstanding 
   commands are in the same transaction.  However, a Subtract command 
   may be issued at any time.  In consequence, a Media Gateway may 
   sometimes receive a Modify command that applies to a previously 
   subtracted Termination.  Such commands should be ignored, and an 
   error code should be returned. 
    
   3.   For transport that do not guarantee in sequence delivery of 
   messages (ie. UDP), on a given Termination, there should normally be 
   at most one outstanding Notify command at any time. 
    
   4.   In some cases, an implicitly or explicitly wildcarded Subtract 
   command that applies to a group of Terminations may step in front of 
   a pending Add command.  The Media Gateway Controller should 
   individually delete all Terminations for which an Add command was 
   pending at the time of the global Subtract command.  Also, new Add 
     
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   commands for Terminations named by the wild-carding (or implied in a 
   Multiplex descriptor) should not be sent until the wild-carded 
   Subtract command is acknowledged. 
    
   5.   AuditValue and AuditCapability are not subject to any 
   sequencing. 
    
   6.   ServiceChange shall always be the first command sent by a MG as 
   defined by the restart procedure. Any other command or response must 
   be delivered after this ServiceChange command.  
    
   These rules do not affect the command responder, which should always 
   respond to commands. 
    
9.2     Protection against Restart Avalanche 
    
   In the event that a large number of Media Gateways are powered on 
   simultaneously and they were to all initiate a ServiceChange 
   transaction, the Media Gateway Controller would very likely be 
   swamped, leading to message losses and network congestion during the 
   critical period of service restoration. In order to prevent such 
   avalanches, the following behavior is suggested: 
    
   1.   When a Media Gateway is powered on, it should initiate a 
   restart timer to a random value, uniformly distributed between 0 and 
   a maximum waiting delay (MWD). Care should be taken to avoid 
   synchronicity of the random number generation between multiple Media 
   Gateways that would use the same algorithm. 
    
   2.   The Media Gateway should then wait for either the end of this 
   timer or the detection of a local user activity, such as for example 
   an off-hook transition on a residential Media Gateway. 
    
   3.   When the timer elapses, or when an activity is detected, the 
   Media Gateway should initiate the restart procedure. 
    
   The restart procedure simply requires the MG to guarantee that the 
   first message that the Media Gateway Controller sees from this MG is 
   a ServiceChange message informing the Media Gateway Controller about 
   the restart 
    
   Note - The value of MWD is a configuration parameter that depends on 
   the type of the Media Gateway. The following reasoning may be used 
   to determine the value of this delay on residential gateways. 
    
   Media Gateway Controllers are typically dimensioned to handle the 
   peak hour traffic load, during which, in average, 10% of the lines 
   will be busy, placing calls whose average duration is typically 3 
   minutes.  The processing of a call typically involves 5 to 6 Media 
   Gateway Controller transactions between each Media Gateway and the 
   Media Gateway Controller.  This simple calculation shows that the 
   Media Gateway Controller is expected to handle 5 to 6 transactions 
   for each Termination, every 30 minutes on average, or, to put it 
   otherwise, about one transaction per Termination every 5 to 6 
     
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   minutes on average.  This suggests that a reasonable value of MWD 
   for a residential gateway would be 10 to 12 minutes.  In the absence 
   of explicit configuration, residential gateways should adopt a value 
   of 600 seconds for MWD. 
    
   The same reasoning suggests that the value of MWD should be much 
   shorter for trunking gateways or for business gateways, because they 
   handle a large number of Terminations, and also because the usage 
   rate of these Terminations is much higher than 10% during the peak 
   busy hour, a typical value being 60%.  These Terminations, during 
   the peak hour, are this expected to contribute about one transaction 
   per minute to the Media Gateway Controller load. A reasonable 
   algorithm is to make the value of MWD per "trunk" Termination six 
   times shorter than the MWD per residential gateway, and also 
   inversely proportional to the number of Terminations that are being 
   restarted. For example MWD should be set to 2.5 seconds for a 
   gateway that handles a T1 line, or to 60 milliseconds for a gateway 
   that handles a T3 line. 
    
    
10.     SECURITY CONSIDERATIONS 
    
   This section covers security when using the protocol in an IP 
   environment. 
    
10.1    Protection of Protocol Connections 
    
   A security mechanism is clearly needed to prevent unauthorized 
   entities from using the protocol defined in this document for 
   setting up unauthorized calls or interfering with authorized calls.  
   The security mechanism for the protocol when transported over IP 
   networks is IPsec [RFC2401 to RFC2411].  
    
   The AH header [RFC2402] affords data origin authentication, 
   connectionless integrity and optional anti-replay protection of 
   messages passed between the MG and the MGC. The ESP header [RFC2406] 
   provides confidentiality of messages, if desired. For instance, the 
   ESP encryption service should be requested if the session 
   descriptions are used to carry session keys, as defined in SDP.  
    
   Implementations of the protocol defined in this document employing 
   the ESP header SHALL comply with section 5 of [RFC2406], which 
   defines a minimum set of algorithms for integrity checking and 
   encryption. Similarly, implementations employing the AH header SHALL 
   comply with section 5 of [RFC2402], which defines a minimum set of 
   algorithms for integrity checking using manual keys. 
    
   Implementations SHOULD use IKE [RFC2409] to permit more robust 
   keying options. Implementations employing IKE SHOULD support 
   authentication with RSA signatures and RSA public key encryption.  
    
     
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10.2    Interim AH scheme 
    
   Implementation of IPsec requires that the AH or ESP header be 
   inserted immediately after the IP header. This cannot be easily done 
   at the application level.  Therefore, this presents a deployment 
   problem for the protocol defined in this document where the 
   underlying network implementation does not support IPsec. 
      
   As an interim solution, an optional AH header is defined within the 
   H.248 protocol header. The header fields are exactly those of the 
   SPI, SEQUENCE NUMBER and DATA fields as defined in [RFC2402]. The 
   semantics of the header fields are the same as the "transport mode" 
   of [RFC2402], except for the calculation of the Integrity Check 
   value (ICV). In IPsec, the ICV is calculated over the entire IP 
   packet including the IP header. This prevents spoofing of the IP 
   addresses.  To retain the same functionality, the ICV calculation 
   should be performed across all the transactions (concatenated) in 
   the message prepended by a synthesized IP header consisting of a 32 
   bit source IP address, a 32 bit destination address and a 16 bit UDP 
   destination port encoded as 20 hex digits. When the interim AH 
   mechanism is employed when TCP is the transport Layer, the UDP Port 
   above becomes the TCP port, and all other operations are the same.  
    
   Implementations of the H.248 protocol SHALL implement IPsec where 
   the underlying operating system and the transport network supports 
   IPsec.  Implementations of the protocol using IPv4 SHALL implement 
   the interim AH scheme. However, this interim scheme SHALL NOT be 
   used when the underlying network layer supports IPsec. IPv6 
   implementations are assumed to support IPsec and SHALL NOT use the 
   interim AH scheme. 
    
   All implementations of the interim AH mechanism SHALL comply with 
   section 5 of [RFC2402] which defines a minimum set of algorithms for 
   integrity checking using manual keys.  
    
   The interim AH interim scheme does not provide protection against 
   eavesdropping; thus forbidding third parties from monitoring the 
   connections set up by a given termination. Also, it does not provide 
   protection against replay attacks.  These procedures do not 
   necessarily protect against denial of service attacks by misbehaving 
   MGs or misbehaving MGCs. However, they will provide an 
   identification of these misbehaving entities, which should then be 
   deprived of their authorization through maintenance procedures. 
    
10.3    Protection of Media Connections 
    
   The protocol allows the MGC to provide MGs with "session keys" that 
   can be used to encrypt the audio messages, protecting against 
   eavesdropping. 
    
   A specific problem of packet networks is "uncontrolled barge-in". 
   This attack can be performed by directing media packets to the IP 
   address and UDP port used by a connection. If no protection is 
     
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   implemented, the packets must be decompressed and the signals must 
   be played on the "line side". 
    
   A basic protection against this attack is to only accept packets 
   from known sources, checking for example that the IP source address 
   and UDP source port match the values announced in the Remote 
   Descriptor.  This has two inconveniences: it slows down connection 
   establishment and it can be fooled by source spoofing: 
    
   ¦    To enable the address-based protection, the MGC must obtain the 
   remote session description of the egress MG and pass it to the 
   ingress MG.  This requires at least one network roundtrip, and 
   leaves us with a dilemma: either allow the call to proceed without 
   waiting for the round trip to complete, and risk for example, 
   "clipping" a remote announcement, or wait for the full roundtrip and 
   settle for slower call-set-up procedures. 
    
   ¦    Source spoofing is only effective if the attacker can obtain 
   valid pairs of source destination addresses and ports, for example 
   by listening to a fraction of the traffic. To fight source spoofing, 
   one could try to control all access points to the network.  But this 
   is in practice very hard to achieve. 
    
   An alternative to checking the source address is to encrypt and 
   authenticate the packets, using a secret key that is conveyed during 
   the call set-up procedure. This will not slow down the call set-up, 
   and provides strong protection against address spoofing. 
    
    
11.      MG-MGC CONTROL INTERFACE 
   
   The control association between MG and MGC is initiated at MG cold 
   start, and announced by a ServiceChange message, but can be changed 
   by subsequent events, such as failures or manual service events.  
   While the protocol does not have an explicit mechanism to support 
   multiple MGCs controlling a physical MG, it has been designed to 
   support the multiple logical MG (within a single physical MG) that 
   can be associated with different MGCs. 
    
11.1    Multiple Virtual MGs 
    
   A physical Media Gateway may be partitioned into one or more Virtual 
   MGs.  A virtual MG consists of a set of statically partitioned 
   physical Terminations and/or sets of ephemeral Terminations.  A 
   physical Termination is controlled by one MGC.  The model does not 
   require that other resources be statically allocated, just 
   Terminations.  The mechanism for allocating Terminations to virtual 
   MGs is a management method outside the scope of the protocol.  Each 
   of the virtual MGs appears to the MGC as a complete MG client.  
    
   A physical MG may have only one network interface, which must be 
   shared across virtual MGs.  In such a case, the packet/cell side 
   Termination is shared.  It should be noted however, that in use, 
   such interfaces require an ephemeral instance of the Termination to 
     
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   be created per flow, and thus sharing the Termination is 
   straightforward.  This mechanism does lead to a complication, namely 
   that the MG must always know which of its controlling MGCs should be 
   notified if an event occurs on the interface. 
    
   In normal operation, the Virtual MG will be instructed by the MGC to 
   create network flows (if it is the originating side), or to expect 
   flow requests (if it is the terminating side), and no confusion will 
   arise.  However, if an unexpected event occurs, the Virtual MG must 
   know what to do with respect to the physical resources it is 
   controlling. 
    
   If recovering from the event requires manipulation of a physical 
   interface's state, only one MGC should do so.  These issues are 
   resolved by allowing any of the MGCs to create EventsDescriptors to 
   be notified of such events, but only one MGC can have read/write 
   access to the physical interface properties; all other MGCs have 
   read-only access.  The management mechanism is used to designate 
   which MGC has read/write capability, and is designated the Master 
   MGC. 
    
   Each virtual MG has its own Root Termination.  In most cases the 
   values for the properties of the Root Termination are independently 
   settable by each MGC.  Where there can only be one value, the 
   parameter is read-only to all but the Master MGC. 
   ServiceChange may only be applied to a Termination or set of 
   Terminations partitioned to the Virtual MG or created (in the case 
   of ephemeral Terminations) by that Virtual MG.   
    
11.2    Cold Start 
    
   A MG is pre-provisioned by a management mechanism outside the scope 
   of this protocol with a Primary and (optionally) an ordered list of 
   Secondary MGCs.  Upon a cold start of the MG, it will issue a 
   ServiceChange command with a "Restart" method, on the Root 
   Termination to its primary MGC.  If the MGC accepts the MG, it sends 
   a Transaction Reply not including a ServiceChangeMgcId parameter.  
   If the MGC does not accept the MG's registration, it sends a 
   Transaction Reply, providing the address of an alternate MGC to be 
   contacted by including a ServiceChangeMgcId parameter. 
    
   If the MG receives a Transaction Reply that includes a 
   ServiceChangeMgcId parameter, it sends a ServiceChange to the MGC 
   specified in the ServiceChangeMgcId. It continues this process until 
   it gets a controlling MGC to accept its registration, or it fails to 
   get a reply.  Upon failure to obtain a reply, either from the 
   Primary MGC, or a designated successor, the MG tries its pre-
   provisioned Secondary MGCs, in order.  If the MG is unable to  
   establish a control relationship with any MGC, it shall wait a 
   random amount of time as described in section 9.2 and then start 
   contacting its primary, and if necessary, its secondary MGCs again. 
    
   It is possible that the reply to a ServiceChange with Restart will 
   be lost, and a command will be received by the MG prior to the 
     
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   receipt of the ServiceChange response.  The MG shall issue error 505 
   “ Command Received before Restart Response. 
    
11.3    Negotiation of Protocol Version 
    
   The first ServiceChange command from an MG shall contain the version 
   number of the protocol supported by the MG in the 
   ServiceChangeVersion parameter. Upon receiving such a message, if 
   the MGC supports only a lower version, then the MGC shall send a 
   ServiceChangeReply with the lower version and thereafter all the 
   messages between MG and MGC shall conform to the lower version of 
   the protocol.  If the MG is unable to comply and it has established 
   a transport connection to the MGC, it should close that connection.  
   In any event, it should reject all subsequent requests from the MGC 
   with Error 406 Version Not supported.  
    
   If the MGC supports a higher version than the MG but is able to 
   support the lower version proposed by the MG, it shall send a 
   ServiceChangeReply with the lower version and thereafter all the 
   messages between MG and MGC shall conform to the lower version of 
   the protocol. If the MGC is unable to comply, it shall reject the 
   association, with Error 406 Version Not Supported. 
    
   Protocol version negotiation may also occur at "handoff" and 
   "failover" ServiceChanges. 
    
   When extending the protocol with new versions, the following rules 
   should be followed. 
    
   1.   Existing protocol elements, i.e., procedures, parameters, 
   descriptor, property,  values, should not be changed unless a 
   protocol error needs to be corrected or it becomes necessary to 
   change the operation of the service that is being supported by the 
   protocol. 
    
   2.   The semantics of a command, a parameter, descriptor, property, 
   value should not be changed. 
    
   3.   Established rules for formatting and encoding messages and 
   parameters should not be modified. 
    
   4.   When information elements are found to be obsolete they can be 
   marked as not used. However, the identifier for that information 
   element will be marked as reserved. In that way it can not be used 
   in future versions. 
    
11.4    Failure of an MG 
    
   If a MG fails, but is capable of sending a message to the MGC, it 
   sends a ServiceChange with an appropriate method (graceful or 
   forced) and specifies the Root TerminationID.  When it returns to 
   service, it sends a ServiceChange with a "Restart" method. 
    
     
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   Allowing the MGC to send duplicate messages to both MGs accommodates 
   pairs of MGs that are capable of redundant failover of one of the 
   MGs.  Only the Working MG shall accept or reject transactions.  Upon 
   failover, the Primary MG sends a ServiceChange command with a 
   "Failover" method and a "MG Impending Failure" reason.  The MGC then 
   uses the secondary MG as the active MG.  When the error condition is 
   repaired, the Working MG can send a "ServiceChange" with a "Restart" 
   method.  Redundant failover MGs with the current protocol definition 
   requires a reliable transport, and knowledge in the MGC of the 
   redundancy at the MG. 
    
11.5    Failure of an MGC 
    
   If the MG detects a failure of its controlling MGC, it attempts to 
   contact the next MGC on its pre-provisioned list.  It starts its 
   attempts at the beginning (Primary MGC), unless that was the MGC 
   that failed, in which case it starts at its first Secondary MGC.  It 
   sends a ServiceChange message with a "Failover" method and a " MGC 
   Impending Failure" reason. If the MG is unable to establish a 
   control relationship with any MGC, it shall wait a random amount of 
   time as described in section 9.2 and then start contacting its 
   primary, and if necessary, its secondary MGCs again. When contacting 
   its previously controlling MGC the MG sends the ServiceChange 
   message with ŸDisconnected÷ method.   
    
   In partial failure, or manual maintenance reasons, an MGC may wish 
   to direct its controlled MGs to use a different MGC.  To do so, it 
   sends a ServiceChange method to the MG with a "HandOff" method, and 
   its designated replacement in ServiceChangeMgcId. If "Handoff" is 
   supported the MG shall send a ServiceChange message with a "Handoff" 
   method and a "MGC directed change" reason to the designated MGC.  If 
   it fails to get a reply from the designated MGC,  the MG shall 
   behave as if its MGC failed, and start contacting secondary MGCs as 
   specified in the previous paragraph.  If the MG is unable to 
   establish a control relationship with any MGC, it shall wait a 
   random amount of time as described in section 9.2 and then start 
   contacting its primary, and if necessary, its secondary MGCs again. 
    
   No recommendation is made on how the MGCs involved in the Handoff 
   maintain state information; this is considered to be out of scope of 
   this recommendation. The MGC and MG may take the following steps 
   when Handoff occurs.  When the MGC initiates a HandOff, the handover 
   should be transparent to Operations on the Media Gateway.  
   Transactions can be executed in any order, and could be in progress 
   when the ServiceChange is executed.  Accordingly, commands in 
   progress continue, transaction replies are sent to the new MGC 
   (after a new control association is established), and the MG should 
   expect outstanding transaction replies from the new MGC.  No new 
   messages shall be sent to the new MGC until the control association 
   is established.  Repeated transaction requests shall be directed to 
   the new MGC.  The MG shall maintain state on all terminations and 
   contexts. 
    
     
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   It is possible that the MGC could be implemented in such a way that 
   a failed MGC is replaced by a working MGC where the identity of the 
   new MGC is the same as the failed one.  In such a case, 
   ServiceChangeMgcId would be specified with the previous value and 
   the MG shall behave as if the value was changed, and send a 
   ServiceChange message, as above. 
    
   Pairs of MGCs that are capable of redundant failover can notify the 
   controlled MGs of the failover by the above mechanism. 
 
12.     PACKAGE DEFINITION 
    
   The primary mechanism for extension is by means of Packages.  
   Packages define additional Properties that may occur on Terminations 
   and contexts and Events, Signals and Statistics that may occur on 
   Terminations.  
    
   Packages defined by IETF will appear in separate RFCs. 
    
   Packages defined by ITU-T may appear in the relevant recommendations 
   (e.g. as annexes). 
    
   1.   A public document or a standard forum document, which can be 
   referenced as the document that describes the package following the 
   guideline above, should be specified.   
    
   2.   The document shall specify the version of the Package that it 
   describes. 
    
   3.   The document should be available on a public web server and 
   should have a stable URL. The site should provide a mechanism to 
   provide comments and appropriate responses should be returned.  
    
12.1    Guidelines for defining packages 
    
   Packages define Properties, Events, Signals, and Statistics. 
    
   Packages may also define new error codes according to the guidelines 
   given in section 13.2. This is a matter of documentary convenience: 
   the package documentation is submitted to IANA in support of the 
   error code registration. If a package is modified, it is unnecessary 
   to provide IANA with a new document reference in support of the 
   error code unless the description of the error code itself is 
   modified.  
    
   Names of all such defined constructs shall consist of the PackageID 
   (which uniquely identifies the package) and the ID of the item 
   (which uniquely identifies the item in that package).  In the text 
   encoding the two shall be separated by a forward slash ("/") 
   character. Example: togen/playtone is the text encoding to refer to 
   the play tone signal in the tone generation package. 
    
   When packages are extended, the properties, events, signals and 
   statistics defined in the base package can be referred to using 
     
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   either the extended package name.  For example, if Package A defines 
   event e1, and Package B extends Package A, then B/e1 is an event for 
   a termination implementing Package B. By definition, the MG MUST 
   also implement the base Package, but it is optional to publish the 
   base package as an allowed interface.  If it does publish  A, then A 
   would be reported on the Package Descriptor in AuditValue as well as 
   B, and event A/e1 would be available on a termination.  If the MG 
   does not publish A, then only B/e1 would be available.  If published 
   through AuditValue, A/e1 and B/e1 are the same event.  
    
   For the purpose of improved interoperability and backward 
   compatibility, an MG MAY publish all Packages supported by its 
   Terminations, including base Packages from which extended Packages 
   are derived.  An exception to this is in cases where the base 
   packages are expressly designed to be extended by others, not 
   directly controlled, and may not have any function on their own or 
   be nonsensical on their own, in which case the MG SHOULD NOT publish 
   the base Packages. 
    
   A Package will contain the following sections: 
    
12.1.1  Package 
    
   Overall description of the package, specifying: 
    
   Package Name: only descriptive,  
    
   PackageID:  Is an identifier 
    
   Description:  
    
   Version:  
        A new version of a package can only add additional Properties, 
        Events, Signals, Statistics and new possible values for an 
        existing parameter described in the original package. No 
        deletions or modifications shall be allowed. A version is  an 
        integer in the range from 1 to 99. 
    
   Extends (Optional):  
        A package may extend an existing package. The version of the 
        original package must be specified. When a package extends 
        another package it shall only add additional Properties, 
        Events, Signals, Statistics and new possible values for an 
        existing parameter described in the original package. An 
        extended package shall not redefine or overload an identifier 
        defined in the original package and packages it may have
        extended (multiple levels of extension).  Hence, if package B 
        version 1 extends package A version 1, version 2 of B will not 
        be able to extend the A version 2 if A version 2 defines a name 
        already in B version 1. 
    
12.1.2  Properties 
    
   Properties defined by the package, specifying: 
     
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        Property Name: only descriptive. 
    
        PropertyID:  Is an identifier 
    
        Description: 
    
        Type: One of: 
                Boolean 
         
                String: UTF-8 string 
         
                Octet String: Octet String: A number of octets.  See 
                Annex A and B.3 for encoding 
              
                Integer: 4 byte signed integer 
         
                Double: 8 byte signed integer 
         
                Character: Unicode UTF-8 encoding of a single letter.  
                        Could be more than one octet. 
         
                Enumeration: One of a list of possible unique values 
                (See 12.3) 
              
                Sub-list: A list of several values from a list. The 
                type of sub-list should also be specified in the 
                package chosen from the types specified in this section 
                with the exception of sub-list, e.g., Type: sub“list of 
                enumeration.  The encoding of sub-lists is specified in 
                Annexes A and B. 
                 
        Possible Values: 
         
        Defined in:  
                Which H.248 descriptor the property is defined in.  
                LocalControl is for stream dependent properties. 
                TerminationState is for stream independent properties. 
                ContextAttribute is for properties which affect the 
                context as a whole ie. mixing properties. These are 
                expected to be the most common cases, but it is 
                possible for properties to be defined in other 
                descriptors. Context properties MUST be defined in the 
                ContextAttribute descriptor. 
         
        Characteristics: Read / Write or both, and (optionally), 
        global:  
                Indicates whether a property is read-only, or read-
                write, and if it is global.  If Global is omitted, the 
                property is not global.  If a property is declared as 
                global, the value of the property is shared by all 
                terminations realizing the package. If a context 
                property is declared as global the property is shared 
                by all contexts realizing the package. 
     
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12.1.3  Events 
    
   Events defined by the package, specifying: 
    
        Event name: only descriptive. 
    
        EventID:  Is an identifier 
    
        Description: 
    
        EventsDescriptor Parameters:  
             Parameters used by the MGC to configure the event, and 
             found in the EventsDescriptor.  See section 12.2. 
    
        ObservedEventsDescriptor Parameters:  
             Parameters returned to the MGC in  Notify requests and in 
             replies to command requests from the MGC that audit 
             ObservedEventsDescriptor, and found in the 
             ObservedEventsDescriptor.  See section 12.2. 
    
12.1.4  Signals 
    
   Signals defined by the package, specifying: 
    
        Signal Name: only descriptive. 
         
        SignalID:  Is an identifier. SignalID is used in a 
        SignalsDescriptor 
         
        Description 
         
        SignalType: One of: 
                        OO (On/Off)  
                        TO (TimeOut) 
                        BR (Brief) 
        Note: SignalType may be defined such that it is dependent on 
        the value of one or more parameters. Signals that would be 
        played with SignalType BR or TO should have a default duration. 
        The package has to define the default duration and signalType.  
         
        Duration: in hundredths of seconds 
         
        Additional Parameters: See section 12.2 
         
12.1.5  Statistics 
    
   Statistics defined by the package, specifying: 
        Statistic name: only descriptive. 
    
        StatisticID:  Is an identifier 
        StatisticID is used in a StatisticsDescriptor 
    
        Description 
     
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        Units: unit of measure, e.g. milliseconds, packets 
    
12.1.6  Procedures 
    
   Additional guidance on the use of the package. 
    
12.2    Guidelines to defining  Properties, Statistics and Parameters 
        to Events and Signals. 
  
   Parameter Name: only descriptive 
    
   ParameterID: Is an identifier. The textual ParameterID of parameters 
   to Events and Signals shall not start with "EPA" and "SPA", 
   respectively. The textual ParameterID shall also not be "ST", 
   "Stream", "SY", "SignalType", "DR", "Duration", "NC", 
   "NotifyCompletion", "KA", "Keepactive", "EB", "Embed", "DM" or 
   "DigitMap". 
    
   Type: One of: 
      Boolean 
         
      String: UTF-8 octet string 
         
      Octet String: Octet String: A number of octets.  See Annex A and 
      B.3 for encoding 
                 
      Integer: 4 octet signed integer 
       
      Double: 8 octet signed integer 
       
      Character: Unicode UTF-8 encoding of a single letter. Could be 
      more than one octet. 
       
      Enumeration: One of a list of possible unique values (See 12.3) 
       
      Sub-list: A list of several values from a list (not supported for 
      statistics). The type of sub-list should also be specified in the 
      package chosen from the types specified in this section with the 
      exception of sub-list, e.g., Type: sub “list of enumeration.  The 
      encoding of sub-lists is specified in Annexes 
    
   Possible values: 
    
   Description: 
         
12.3    Lists 
    
   Possible values for parameters include enumerations.  Enumerations 
   may be defined in a list.  It is recommended that the list be IANA 
   registered so that packages that extend the list can be defined 
   without concern for conflicting names. 
    
     
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12.4    Identifiers 
  
   Identifiers in text encoding shall be strings of up to 64 
   characters, containing no spaces, starting with an alphabetic 
   character and consisting of alphanumeric characters and / or digits, 
   and possibly including the special character underscore ("_"). 
   Identifiers in binary encoding are 2 octets long. 
   Both text and binary values shall be specified for each identifier, 
   including identifiers used as values in enumerated types. 
    
12.5    Package Registration 
    
   A package can be registered with IANA for interoperability reasons.  
   See section 14 for IANA considerations.  
    
    
13.     PROFILE DEFINITION 
    
   Profiles may be specified to further define how the H.248 protocol 
   is used and what functionality is supported by a MG. The profile 
   itself specifies what options associated with H.248 have been used. 
   For example: transport and packages used for an application.  
    
   A profile is identified by a name (IANA registered) and a Version. A 
   name shall be a string up to 64 characters long. Version shall be 1 
   to 99. 
    
   The profile itself is a document that indicates the options for a 
   particular application. There is no set format for this document. 
   The only mandatory element is that there should be a section 
   indicating the Name and Version and a summary of the profile. 
    
   Whilst the first two points below are the only mandatory sections, 
   the following points should be considered for inclusion: 
    
   ¹    Profile Identification: The name of the profile that is sent in 
   the service change command. 
    
   ¹    Summary: A description of what the profile is. 
    
   ¹    Naming Conventions: 
    
   MGC/MG Naming Conventions: Addressing associated with the names of 
   the MGC / MG. 
    
   Termination Names: The termination identity structure. 
    
   Digit Map Names: The names of any digit maps. 
    
   ¹    Topology Descriptor: Is the topology descriptor used by this 
   profile? 
    
   ¹    TimeStamps: Specifies whether timestamps will be used in the 
   ServiceChange and/or Notify commands. 
     
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   ¹    Transaction Timers: Specifies the values of the transaction 
   timers. 
    
   ¹    Transport: Specifies what H.248 transports are supported by the 
   profile. 
    
   ¹    Encoding: Specifies what encoding is supported by the profile.  
    
   ¹    Mandatory support of SDP and H.248 annex C information 
   elements: Specifies what SDP attributes and H.248 Annex C 
   information elements are to be supported. 
    
   ¹    Packages: Specifies the packages that are supported in this 
   profile. 
    
   Mandatory “ specifies the packages that shall be supported in this 
   profile. 
    
   Optional “ specifies the packages that may be supported in the 
   profile. 
    
   Package Provisioning Information “ specifies the values of 
   properties which are specified as provisioned. E.g. H.248 Annex K 
   Announcement Names & Number of Cycles. 
    
   ¹    Security: Specifies the security mechanisms used. 
    
   Procedures: Specifies the procedures that are associated with the 
   profile. 
    
    
14.      IANA CONSIDERATIONS 
    
14.1    Packages 
    
   The following considerations SHALL be met to register a package with 
   IANA: 
    
   1.   A unique string name, unique serial number and version number 
   is registered for each package.  The string name is used with text 
   encoding.  The serial number shall be used with binary encoding.  
   Serial Numbers 0x8000 to 0xffff are reserved for private use. Serial 
   number 0 is reserved. 
    
   2.   A contact name, email and postal addresses for that contact 
   shall be specified.  The contact information shall be updated by the 
   defining organization as necessary. 
    
   3.   A reference to a document that describes the package, which 
   should be public:  
    
   The document shall specify the version of the Package that it 
   describes. 
     
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   If the document is public, it should be located on a public web 
   server and should have a stable URL. The site should provide a 
   mechanism to provide comments and appropriate responses should be 
   returned.  
    
   4.   Packages registered by other than recognized standards bodies 
   shall have a minimum package name length of 8 characters 
    
   5.   All other package names are first come-first served if all 
   other conditions are met 
    
14.2    Error Codes 
    
   The following considerations SHALL be met to register an error code 
   with IANA: 
    
   1.   An error number and a one line (80 character maximum) string is 
   registered for each error. 
    
   2.   A complete description of the conditions under which the error 
   is detected shall be included in a publicly available document.  The 
   description shall be sufficiently clear to differentiate the error 
   from all other existing error codes.   
    
   3.   The document should be available on a public web server and 
   should have a stable URL.  
    
   4.   Error numbers registered by recognized standards bodies shall 
   have 3 or 4 character error numbers. 
    
   5.   Error numbers registered by all other organizations or 
   individuals shall have 4 character error numbers. 
    
   6.   An error number shall not be redefined, nor modified except by 
   the organization or individual that originally defined it, or their 
   successors or assigns. 
    
14.3    ServiceChange Reasons 
    
   The following considerations SHALL be met to register service change 
   reason with IANA: 
    
   1.   A one phrase, 80-character maximum, unique reason code is 
   registered for each reason. 
    
   2.   A complete description of the conditions under which the reason 
   is used is detected shall be included in a publicly available 
   document.  The description shall be sufficiently clear to 
   differentiate the reason from all other existing reasons.   
    
   3.   The document should be available on a public web server and 
   should have a stable URL.  
    
     
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14.4    Profiles 
    
   The following considerations SHALL be met to register a Profile with 
   IANA: 
    
   1.   A unique string name and version number is registered for each 
   profile.  
     
   2.   A contact name, email and postal addresses for that contact 
   shall be specified.  The contact information shall be updated by the 
   defining organization as necessary.  
    
   3.   Profiles registered by other than recognized standards bodies 
   shall have a minimum profile name length of 6 characters. 
    
   4.   Profile names containing a wildcard "*"on the end of their 
   names shall be accepted if the first 6 characters are fully 
   specified. It is assumed that the organisation that was issued with 
   the Profile name will manage the namespace associated with the 
   wildcard. IANA shall not issue other profiles names within "name*" 
   range. 
    
   5.   All other Profile names are first come-first served if all 
   other conditions are met. 
     
     
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ANNEX A BINARY ENCODING OF THE PROTOCOL (NORMATIVE) 
    
   This Annex specifies the syntax of messages using the notation 
   defined in ASN.1 [ITU-T Recommendation X.680 (1997): Information 
   Technology - Abstract Syntax Notation One (ASN.1) - Specification of 
   basic notation.]. Messages shall be encoded for transmission by 
   applying the basic encoding rules specified in [ITU-T Recommendation 
   X.690(1994) Information Technology - ASN.1  Encoding Rules: 
   Specification  of  Basic  Encoding Rules  (BER)].  
    
A.1     Coding of wildcards 
    
   The use of wildcards ALL and CHOOSE is allowed in the protocol.  
   This allows a MGC to partially specify Termination IDs and let the 
   MG choose from the values that conform to the partial specification.  
   Termination IDs may encode a hierarchy of names.  This hierarchy is 
   provisioned. For instance, a TerminationID may consist of a trunk 
   group, a trunk within the group and a circuit.  Wildcarding must be 
   possible at all levels.  The following paragraphs explain how this 
   is achieved. 
    
   The ASN.1 description uses octet strings of up to 8 octets in length 
   for Termination IDs.  This means that Termination IDs consist of at
   most 64 bits.  A fully specified Termination ID may be preceded by a 
   sequence of wildcarding fields.  A wildcarding field is one octet in 
   length.  Bit 7 (the most significant bit) of this octet specifies 
   what type of wildcarding is invoked:  if the bit value equals 1, 
   then the ALL wildcard is used; if the bit value if 0, then the 
   CHOOSE wildcard is used.  Bit 6 of the wildcarding field specifies 
   whether the wildcarding pertains to one level in the hierarchical 
   naming scheme (bit value 0) or to the level of the hierarchy 
   specified in the wildcarding field plus all lower levels (bit value 
   1).  Bits 0 through 5 of the wildcarding field specify the bit 
   position in the Termination ID at which the wildcarding starts. 
    
   We illustrate this scheme with some examples.  In these examples, 
   the most significant bit in a string of bits appears on the left 
   hand side. 
    
   Assume that Termination IDs are three octets long and that each 
   octet represents a level in a hierarchical naming scheme.  A valid 
   Termination ID is 
        00000001 00011110 01010101. 
    
   Addressing ALL names with prefix 00000001 00011110 is done as 
   follows: 
        wildcarding field: 10000111 
        Termination ID: 00000001 00011110 xxxxxxxx. 
    
   The values of the bits labeled "x" is irrelevant and shall be 
   ignored by the receiver. 
    
   Indicating to the receiver that is must choose a name with 00011110 
   as the second octet is done as follows: 
     
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        wildcarding fields: 00010111 followed by 00000111 
        Termination ID: xxxxxxxx 00011110 xxxxxxxx. 
    
   The first wildcard field indicates a CHOOSE wildcard for the level 
   in the naming hierarchy starting at bit 23, the highest level in our 
   assumed naming scheme.  The second wildcard field indicates a CHOOSE 
   wildcard for the level in the naming hierarchy starting at bit 7, 
   the lowest level in our assumed naming scheme. 
    
   Finally, a CHOOSE-wildcarded name with the highest level of the name 
   equal to 00000001 is specified as follows: 
        wildcard field: 01001111 
        Termination ID: 0000001 xxxxxxxx xxxxxxxx . 
    
   Bit value 1 at bit position 6 of the first octet of the wildcard 
   field indicates that the wildcarding pertains to the specified level 
   in the naming hierarchy and all lower levels. 
    
   Context IDs may also be wildcarded.  In the case of Context IDs, 
   however, specifying partial names is not allowed.  Context ID 0x0  
   SHALL be used to indicate the NULL Context, Context ID 0xFFFFFFFE 
   SHALL be used to indicate a CHOOSE wildcard, and Context ID 
   0xFFFFFFFF SHALL be used to indicate an ALL wildcard. 
    
   TerminationID 0xFFFFFFFFFFFFFFFF SHALL be used to indicate the ROOT 
   Termination. 
    
A.2     ASN.1 syntax specification 
    
   This section contains the ASN.1 specification of the H.248 protocol 
   syntax. 
    
   NOTE - In case a transport mechanism is used that employs 
   application level framing, the definition of Transaction below 
   changes.  Refer to the annex defining the transport mechanism for 
   the definition that applies in that case. 
    
   NOTE “ The ASN.1 specification below contains a clause defining 
   TerminationIDList as a sequence of TerminationIDs.  The length of 
   this sequence SHALL be one, except possibly when used in 
   contextAuditResult. 
    
   NOTE “ This syntax specification does not enforce all restrictions 
   on element inclusions and values.  Some additional restrictions are 
   stated in comments and other restrictions appear in the text of this 
   recommendation.  These additional restrictions are part of the 
   protocol even though not enforced by this specification. 
    
   NOTE “ The ASN.1 in this section uses OCTET STRING to encode values 
   for property parameter, signal parameter and event parameter values 
   and statistics. The actual types of these values vary and are 
   specified in Annex C or the relevant package definition. 
    
     
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   A value is first ASN.1 BER encoded based on it's type using the 
   table below.  The result of this ASN.1 BER encoding is then encoded 
   as an ASN.1 BER OCTET STRING, "double wrapping" the value. The 
   format specified in Annex C or the package relates to ASN.1 BER 
   encoding according to the following table: 
    
   Type Specified in Package      ASN.1 BER Type 
   String (UTF-8)                 IA5String 
   Integer (4 Octet)              INTEGER 
   Double (8 octet signed int)    INTEGER (Note 3) 
   Character (UTF-8, Note 1)      IA5String 
   Enumeration                    ENUM 
   Boolean                        BOOLEAN 
   Unsigned Integer (Note 2)      INTEGER (Note 3) 
   Octet (String)                 OCTET STRING 
    
   Note 1 : Can be more than one byte 
   Note 2 : Unsigned integer is referenced in Annex C 
   Note 3 : ASN.1 BER encoding of INTEGER does not imply the use of 4 
   bytes. 
    
   See 8.7 X.690 for definition of encoding of Octet String value. 
    
    
   MEDIA-GATEWAY-CONTROL DEFINITIONS AUTOMATIC TAGS::= 
   BEGIN 
    
    
   MegacoMessage ::= SEQUENCE 
   { 
        authHeader      AuthenticationHeader OPTIONAL, 
        mess                    Message 
   } 
    
   AuthenticationHeader ::= SEQUENCE 
   { 
        secParmIndex    SecurityParmIndex, 
        seqNum            SequenceNum, 
        ad              AuthData 
   } 
    
   SecurityParmIndex ::= OCTET STRING(SIZE(4)) 
    
   SequenceNum       ::= OCTET STRING(SIZE(4)) 
    
   AuthData          ::= OCTET STRING (SIZE (12..32)) 
    
   Message ::= SEQUENCE 
   { 
        version         INTEGER(0..99), 
   -- The version of the protocol defined here is equal to 2. 
        mId             MId,    -- Name/address of message originator 
        messageBody             CHOICE 
     
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        { 
                messageError    ErrorDescriptor, 
                transactions    SEQUENCE OF Transaction 
        }, 
        ... 
   } 
    
   MId ::= CHOICE 
   { 
        ip4Address                      IP4Address, 
        ip6Address                      IP6Address, 
        domainName                      DomainName, 
        deviceName                      PathName, 
        mtpAddress                      OCTET STRING(SIZE(2..4)), 
    -- Addressing structure of mtpAddress: 
    --                        0 
    --        |  PC        | NI | 
    --        24 - 14 bits    2 bits 
    -- Note: 14 bits is defined for international use. 
    -- Two national options exist where the point code is 16 or 24   
    -- bits. 
    -- To octet align the mtpAddress the MSBs shall be encoded as 0s. 
         ... 
   } 
    
   DomainName ::= SEQUENCE 
   { 
        name            IA5String, 
   -- The name starts with an alphanumeric digit followed by a 
   -- sequence of alphanumeric digits, hyphens and dots.  No two 
   -- dots shall occur consecutively. 
        portNumber      INTEGER(0..65535) OPTIONAL 
   } 
    
   IP4Address ::= SEQUENCE 
   { 
        address OCTET STRING (SIZE(4)), 
        portNumber      INTEGER(0..65535) OPTIONAL 
   } 
    
   IP6Address ::= SEQUENCE 
   { 
        address OCTET STRING (SIZE(16)), 
        portNumber      INTEGER(0..65535) OPTIONAL 
   } 
    
   PathName ::= IA5String(SIZE (1..64)) 
   -- See section A.3 
    
   Transaction ::= CHOICE 
   { 
        transactionRequest      TransactionRequest, 
        transactionPending      TransactionPending, 
        transactionReply        TransactionReply, 
     
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        transactionResponseAck  TransactionResponseAck, 
        -- use of response acks is dependent on underlying transport 
        ... 
   } 
    
   TransactionId ::= INTEGER(0..4294967295)  -- 32 bit unsigned integer 
    
   TransactionRequest ::= SEQUENCE 
   { 
        transactionId           TransactionId, 
        actions                 SEQUENCE OF ActionRequest, 
        ... 
   } 
    
   TransactionPending ::= SEQUENCE 
   { 
        transactionId           TransactionId, 
        ... 
   } 
    
   TransactionReply ::= SEQUENCE 
   { 
        transactionId           TransactionId, 
        immAckRequired          NULL OPTIONAL, 
        transactionResult       CHOICE 
        { 
             transactionError   ErrorDescriptor, 
             actionReplies      SEQUENCE OF ActionReply 
        }, 
        ... 
   } 
    
   TransactionResponseAck ::= SEQUENCE OF TransactionAck 
   TransactionAck ::= SEQUENCE 
   { 
        firstAck        TransactionId, 
        lastAck TransactionId OPTIONAL 
   } 
    
   ErrorDescriptor ::= SEQUENCE 
   { 
        errorCode       ErrorCode, 
        errorText       ErrorText OPTIONAL 
   } 
    
   ErrorCode ::= INTEGER(0..65535) 
   -- See section 13 for IANA considerations w.r.t. error codes 
    
   ErrorText ::= IA5String 
    
   ContextID ::= INTEGER(0..4294967295) 
    
   -- Context NULL Value: 0 
   -- Context CHOOSE Value: 4294967294 (0xFFFFFFFE)  
     
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   -- Context ALL Value: 4294967295 (0xFFFFFFFF) 
    
    
   ActionRequest ::= SEQUENCE 
   { 
        contextId                       ContextID, 
        contextRequest          ContextRequest OPTIONAL, 
        contextAttrAuditReq     ContextAttrAuditRequest OPTIONAL, 
        commandRequests SEQUENCE OF CommandRequest 
   } 
    
   ActionReply ::= SEQUENCE 
   { 
        contextId               ContextID, 
        errorDescriptor ErrorDescriptor OPTIONAL, 
        contextReply    ContextRequest OPTIONAL, 
        commandReply    SEQUENCE OF CommandReply 
   } 
    
   ContextRequest ::= SEQUENCE 
   { 
        priority        INTEGER(0..15) OPTIONAL, 
        emergency       BOOLEAN OPTIONAL, 
        topologyReq     SEQUENCE OF TopologyRequest OPTIONAL, 
        ..., 
        contextProp     SEQUENCE OF PropertyParm OPTIONAL 
        contextPackages         PackagesDescriptor OPTIONAL 
        ; ContextPackages only to be used in a reply to an audit 
   } 
    
   ContextAttrAuditRequest ::= SEQUENCE 
   { 
   topology     NULL OPTIONAL, 
        emergency       NULL OPTIONAL, 
        priority        NULL OPTIONAL, 
        ..., 
        contextPropAud     SEQUENCE OF IndAudPropertyParm OPTIONAL 
        contextAttrDescriptorCapAud                  NULL OPTIONAL, 
        contextPropCapAud  SEQUENCE OF IndAudPropertyParm OPTIONAL, 
        contextPackagesAud                           NULL OPTIONAL 
   } 
    
   CommandRequest ::= SEQUENCE 
   { 
        command         Command, 
        optional        NULL OPTIONAL, 
        wildcardReturn  NULL OPTIONAL, 
        ... 
   } 
    
   Command ::= CHOICE 
   { 
        addReq                  AmmRequest, 
        moveReq                 AmmRequest, 
     
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        modReq                  AmmRequest, 
        -- Add, Move, Modify requests have the same parameters 
        subtractReq             SubtractRequest, 
        auditCapRequest         AuditRequest, 
        auditValueRequest       AuditRequest, 
        notifyReq               NotifyRequest, 
        serviceChangeReq        ServiceChangeRequest, 
        ... 
   } 
    
   CommandReply ::= CHOICE 
   { 
        addReply                AmmsReply, 
        moveReply               AmmsReply, 
        modReply                AmmsReply, 
        subtractReply           AmmsReply, 
        -- Add, Move, Modify, Subtract replies have the same parameters 
        auditCapReply           AuditReply, 
        auditValueReply         AuditReply, 
        notifyReply             NotifyReply, 
        serviceChangeReply      ServiceChangeReply, 
        ... 
   } 
    
   TopologyRequest ::= SEQUENCE 
   { 
        terminationFrom         TerminationID, 
        terminationTo           TerminationID, 
        topologyDirection       ENUMERATED 
        { 
                bothway(0), 
                isolate(1), 
                oneway(2) 
    
        }, 
        ..., 
        streamID                StreamID OPTIONAL 
   } 
    
   AmmRequest ::= SEQUENCE 
   { 
        terminationID           TerminationIDList, 
        descriptors             SEQUENCE OF     AmmDescriptor, 
        -- At most one descriptor of each type (see AmmDescriptor) 
        -- allowed in the sequence. 
        ... 
   } 
    
   AmmDescriptor ::= CHOICE 
   { 
        mediaDescriptor                 MediaDescriptor, 
        modemDescriptor                 ModemDescriptor, 
        muxDescriptor                   MuxDescriptor, 
        eventsDescriptor                EventsDescriptor, 
     
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        eventBufferDescriptor           EventBufferDescriptor, 
        signalsDescriptor               SignalsDescriptor, 
        digitMapDescriptor              DigitMapDescriptor, 
        auditDescriptor                 AuditDescriptor, 
        ... 
   } 
    
    
   AmmsReply ::= SEQUENCE 
   { 
        terminationID           TerminationIDList, 
        terminationAudit        TerminationAudit OPTIONAL, 
        ... 
   } 
    
   SubtractRequest ::= SEQUENCE 
   { 
        terminationID           TerminationIDList, 
        auditDescriptor         AuditDescriptor OPTIONAL, 
        ... 
   } 
    
   AuditRequest ::= SEQUENCE 
   { 
        terminationID           TerminationID, 
        auditDescriptor         AuditDescriptor, 
        ... 
   } 
    
   AuditReply ::= CHOICE 
   { 
        contextAuditResult      TerminationIDList, 
        error                   ErrorDescriptor, 
        auditResult             AuditResult, 
        ... 
   } 
    
   AuditResult ::= SEQUENCE 
   { 
        terminationID           TerminationID, 
        terminationAuditResult  TerminationAudit 
   } 
    
    
    
   TerminationAudit ::= SEQUENCE OF AuditReturnParameter 
    
   AuditReturnParameter ::= CHOICE 
   { 
        errorDescriptor                 ErrorDescriptor, 
        mediaDescriptor                 MediaDescriptor, 
        modemDescriptor                 ModemDescriptor, 
        muxDescriptor                   MuxDescriptor, 
        eventsDescriptor                EventsDescriptor, 
     
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        eventBufferDescriptor           EventBufferDescriptor, 
        signalsDescriptor               SignalsDescriptor, 
        digitMapDescriptor              DigitMapDescriptor, 
        observedEventsDescriptor        ObservedEventsDescriptor, 
        statisticsDescriptor            StatisticsDescriptor, 
        packagesDescriptor              PackagesDescriptor, 
        emptyDescriptors                AuditDescriptor, 
        ... 
   } 
    
   AuditDescriptor ::= SEQUENCE 
   { 
        auditToken      BIT STRING 
        { 
                muxToken(0), modemToken(1), mediaToken(2), 
                eventsToken(3), signalsToken(4), 
                digitMapToken(5), statsToken(6), 
                observedEventsToken(7), 
                packagesToken(8), eventBufferToken(9) 
        } OPTIONAL, 
        ..., 
        auditPropertyToken SEQUENCE OF IndAuditParameter OPTIONAL, 
   } 
    
   IndAuditParameter ::= CHOICE 
   { 
        indaudmediaDescriptor           IndAudMediaDescriptor, 
        indaudmodemDescriptor           IndAudModemDescriptor, 
        indaudeventsDescriptor          IndAudEventsDescriptor, 
        indaudeventBufferDescriptor     IndAudEventBufferDescriptor, 
        indaudsignalsDescriptor         IndAudSignalsDescriptor, 
        indauddigitMapDescriptor      IndAudDigitMapDescriptor, 
        indaudstatisticsDescriptor    IndAudStatisticsDescriptor, 
        indaudpackagesDescriptor      IndAudPackagesDescriptor, 
   ... 
   } 
    
   IndAudMediaDescriptor ::= SEQUENCE 
   { 
         
        termStateDescr  IndAudTerminationStateDescriptor OPTIONAL, 
        streams CHOICE 
        { 
                oneStream       IndAudStreamParms, 
                multiStream     SEQUENCE OF IndAudStreamDescriptor 
        } OPTIONAL, 
        ... 
   } 
    
   IndAudStreamDescriptor ::= SEQUENCE 
   { 
        streamID                StreamID, 
        streamParms             IndAudStreamParms 
   } 
     
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   IndAudStreamParms ::= SEQUENCE 
   { 
        localControlDescriptor  IndAudLocalControlDescriptor OPTIONAL, 
        localDescriptor         IndAudLocalRemoteDescriptor OPTIONAL, 
        remoteDescriptor        IndAudLocalRemoteDescriptor OPTIONAL, 
        ... 
   } 
    
   IndAudLocalControlDescriptor ::= SEQUENCE 
   { 
        streamMode      NULL OPTIONAL, 
        reserveValue    NULL OPTIONAL, 
        reserveGroup    NULL OPTIONAL, 
        propertyParms   SEQUENCE OF IndAudPropertyParm OPTIONAL, 
        ... 
   } 
    
   IndAudPropertyParm ::= SEQUENCE 
   { 
        name            PkgdName, 
        ... 
   } 
    
   IndAudLocalRemoteDescriptor ::= SEQUENCE 
   { 
        propGroupID INTEGER(0..65535) OPTIONAL, 
        propGrps        IndAudPropertyGroup, 
        ... 
   } 
    
   IndAudPropertyGroup ::= SEQUENCE OF IndAudPropertyParm 
    
   IndAudTerminationStateDescriptor ::= SEQUENCE  
   { 
        propertyParms           SEQUENCE OF IndAudPropertyParm, 
        eventBufferControl      NULL OPTIONAL, 
        serviceState            NULL OPTIONAL, 
        ... 
   } 
    
   IndAudEventsDescriptor ::= SEQUENCE 
   { 
        requestID               RequestID OPTIONAL, 
        pkgdName                PkgdName, 
        streamID                StreamID OPTIONAL, 
        ... 
   } 
    
   IndAudEventBufferDescriptor ::= SEQUENCE 
   { 
        eventName               PkgdName, 
        streamID                StreamID OPTIONAL, 
        ... 
     
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   } 
    
   IndAudSignalsDescriptor ::=CHOICE 
   { 
        signal                  IndAudSignal, 
        seqSigList              IndAudSeqSigList, 
        ... 
   } 
    
   IndAudSeqSigList ::= SEQUENCE 
   { 
        id              INTEGER(0..65535), 
        signalList      IndAudSignal OPTIONAL 
   } 
    
   IndAudSignal ::= SEQUENCE 
   { 
        signalName              PkgdName, 
        streamID                StreamID OPTIONAL, 
        ... 
   } 
    
   IndAudModemDescriptor ::= SEQUENCE 
   { 
        mtl                     NULL,  
        mpl                     IndAudPropertyParm, 
        nonStandardData         NULL OPTIONAL 
   } 
    
   IndAudDigitMapDescriptor ::= SEQUENCE 
   { 
        digitMapName            DigitMapName OPTIONAL 
   } 
    
   IndAudStatisticsDescriptor ::= SEQUENCE  
   { 
        statName                PkgdName 
   } 
    
   IndAudPackagesDescriptor ::= SEQUENCE 
   { 
        packageName             Name, 
        packageVersion  INTEGER(0..99), 
        ... 
   } 
    
   NotifyRequest ::= SEQUENCE 
   { 
        terminationID                   TerminationIDList, 
        observedEventsDescriptor        ObservedEventsDescriptor, 
        errorDescriptor                 ErrorDescriptor OPTIONAL, 
        ... 
   } 
    
     
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   NotifyReply ::= SEQUENCE 
   { 
        terminationID                   TerminationIDList, 
        errorDescriptor                 ErrorDescriptor OPTIONAL, 
        ... 
   } 
    
   ObservedEventsDescriptor ::= SEQUENCE 
   { 
        requestId                       RequestID, 
        observedEventLst                SEQUENCE OF ObservedEvent 
   } 
    
   ObservedEvent ::= SEQUENCE 
   { 
        eventName                       EventName, 
        streamID                        StreamID OPTIONAL, 
        eventParList                    SEQUENCE OF EventParameter, 
        timeNotation                    TimeNotation OPTIONAL, 
        ... 
   } 
    
   EventName ::= PkgdName 
    
   EventParameter ::= SEQUENCE 
   { 
        eventParameterName              Name, 
        value                           Value, 
   -- For use of extraInfo see the comment related to PropertyParm 
        extraInfo CHOICE 
        { 
                relation        Relation, 
                range           BOOLEAN, 
                sublist BOOLEAN 
        } OPTIONAL, 
        ... 
   } 
    
   ServiceChangeRequest ::= SEQUENCE 
   { 
        terminationID                   TerminationIDList, 
        serviceChangeParms              ServiceChangeParm, 
        ... 
   } 
    
   ServiceChangeReply ::= SEQUENCE 
   { 
        terminationID                   TerminationIDList, 
        serviceChangeResult             ServiceChangeResult, 
        ... 
   } 
    
   -- For ServiceChangeResult, no parameters are mandatory.  Hence the 
   -- distinction between ServiceChangeParm and ServiceChangeResParm. 
     
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   ServiceChangeResult ::= CHOICE 
   { 
        errorDescriptor                 ErrorDescriptor, 
        serviceChangeResParms           ServiceChangeResParm 
   } 
    
   WildcardField ::= OCTET STRING(SIZE(1)) 
    
   TerminationID ::= SEQUENCE 
   { 
        wildcard        SEQUENCE OF WildcardField,  
        id              OCTET STRING(SIZE(1..8)), 
        ... 
   } 
   -- See Section A.1 for explanation of wildcarding mechanism. 
   -- Termination ID 0xFFFFFFFFFFFFFFFF indicates the ROOT Termination. 
    
   TerminationIDList ::= SEQUENCE OF TerminationID 
    
   MediaDescriptor ::= SEQUENCE 
   { 
         
        termStateDescr  TerminationStateDescriptor OPTIONAL, 
        streams         CHOICE 
        { 
                oneStream       StreamParms, 
                multiStream     SEQUENCE OF StreamDescriptor 
        } OPTIONAL, 
        ... 
   } 
    
   StreamDescriptor ::= SEQUENCE 
   { 
        streamID                        StreamID, 
        streamParms                     StreamParms 
   } 
    
   StreamParms ::= SEQUENCE 
   { 
        localControlDescriptor         LocalControlDescriptor OPTIONAL, 
        localDescriptor                 LocalRemoteDescriptor OPTIONAL, 
        remoteDescriptor                LocalRemoteDescriptor OPTIONAL, 
        ... 
   } 
    
   LocalControlDescriptor ::= SEQUENCE 
   { 
        streamMode      StreamMode OPTIONAL, 
        reserveValue    BOOLEAN OPTIONAL, 
        reserveGroup    BOOLEAN OPTIONAL, 
        propertyParms   SEQUENCE OF PropertyParm, 
        ... 
   } 
     
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   StreamMode ::= ENUMERATED  
   { 
        sendOnly(0), 
        recvOnly(1), 
        sendRecv(2), 
        inactive(3), 
        loopBack(4), 
                ... 
   } 
    
   -- In PropertyParm, value is a SEQUENCE OF octet string.  When sent 
   -- by an MGC the interpretation is as follows: 
   -- empty sequence means CHOOSE 
   -- one element sequence specifies value 
   -- If the sublist field is not selected, a longer sequence means 
   -- "choose one of the values" (i.e. value1 OR value2 OR ...) 
   -- If the sublist field is selected, 
   -- a sequence with more than one element encodes the value of a 
   -- list-valued property (i.e. value1 AND value2 AND ...). 
   -- The relation field may only be selected if the value sequence 
   -- has length 1.  It indicates that the MG has to choose a value 
   -- for the property. E.g., x > 3 (using the greaterThan 
   -- value for relation) instructs the MG to choose any value larger 
   -- than 3 for property x. 
   -- The range field may only be selected if the value sequence 
   -- has length 2.  It indicates that the MG has to choose a value 
   -- in the range between the first octet in the value sequence and 
   -- the trailing octet in the value sequence, including the 
   -- boundary values. 
   -- When sent by the MG, only responses to an AuditCapability request 
   -- may contain multiple values, a range, or a relation field. 
    
   PropertyParm ::= SEQUENCE 
   { 
        name            PkgdName, 
        value           SEQUENCE OF OCTET STRING, 
        extraInfo       CHOICE 
        { 
                relation        Relation, 
                range           BOOLEAN, 
                sublist BOOLEAN 
        } OPTIONAL, 
        ... 
   } 
    
   Name ::= OCTET STRING(SIZE(2)) 
    
   PkgdName ::= OCTET STRING(SIZE(4)) 
   -- represents Package Name (2 octets) plus Property, Event, 
   -- Signal Names or Statistics ID. (2 octets) 
   -- To wildcard a package use 0xFFFF for first two octets, choose 
   -- is not allowed. To reference native property tag specified in 
   -- Annex C, use 0x0000 as first two octets. 
     
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   -- To wildcard a Property, Event, Signal, or Statistics ID, use  
   -- 0xFFFF for last two octets, choose is not allowed. 
   -- Wildcarding of Package Name is permitted only if Property, Event, 
   -- Signal, or Statistics ID is also wildcarded. 
    
    
   Relation ::= ENUMERATED 
   { 
        greaterThan(0), 
        smallerThan(1), 
        unequalTo(2), 
        ... 
   } 
    
   LocalRemoteDescriptor ::= SEQUENCE 
   { 
        propGrps        SEQUENCE OF PropertyGroup, 
        ... 
   } 
    
   PropertyGroup ::= SEQUENCE OF PropertyParm 
    
   TerminationStateDescriptor ::= SEQUENCE  
   { 
        propertyParms       SEQUENCE OF PropertyParm, 
        eventBufferControl        EventBufferControl OPTIONAL, 
        serviceState        ServiceState OPTIONAL, 
        ... 
   } 
    
   EventBufferControl ::= ENUMERATED 
   { 
        off(0), 
        lockStep(1), 
        ... 
   } 
    
   ServiceState ::= ENUMERATED 
   { 
        test(0), 
        outOfSvc(1), 
        inSvc(2), 
         ... 
   } 
    
   MuxDescriptor   ::= SEQUENCE 
   { 
        muxType                 MuxType, 
        termList        SEQUENCE OF TerminationID, 
        nonStandardData NonStandardData OPTIONAL, 
        ... 
   } 
    
   MuxType ::= ENUMERATED 
     
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   { 
        h221(0), 
        h223(1), 
        h226(2), 
        v76(3), 
        ... 
   } 
    
   StreamID ::= INTEGER(0..65535)  -- 16 bit unsigned integer 
    
   EventsDescriptor ::= SEQUENCE 
   { 
        requestID               RequestID OPTIONAL, 
        -- RequestID must be present if eventList 
        -- is non empty, 
        eventList               SEQUENCE OF RequestedEvent, 
        ... 
   } 
    
   RequestedEvent ::= SEQUENCE 
   { 
        pkgdName        PkgdName, 
        streamID                StreamID OPTIONAL, 
        eventAction     RequestedActions OPTIONAL, 
        evParList       SEQUENCE OF EventParameter, 
        ... 
   } 
    
   RequestedActions ::= SEQUENCE 
   { 
        keepActive                      BOOLEAN OPTIONAL, 
        eventDM                 EventDM OPTIONAL, 
        secondEvent             SecondEventsDescriptor OPTIONAL, 
        signalsDescriptor       SignalsDescriptor OPTIONAL, 
        ... 
   } 
    
    
   EventDM ::= CHOICE 
   {    digitMapName    DigitMapName, 
        digitMapValue   DigitMapValue 
   } 
    
   SecondEventsDescriptor ::= SEQUENCE 
   { 
        requestID               RequestID OPTIONAL, 
        eventList               SEQUENCE OF SecondRequestedEvent, 
        ... 
   } 
    
   SecondRequestedEvent ::= SEQUENCE 
   { 
        pkgdName                PkgdName, 
        streamID                StreamID OPTIONAL, 
     
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        eventAction             SecondRequestedActions OPTIONAL, 
        evParList               SEQUENCE OF EventParameter, 
        ... 
   } 
    
   SecondRequestedActions ::= SEQUENCE 
   { 
        keepActive                      BOOLEAN OPTIONAL, 
        eventDM                 EventDM OPTIONAL, 
        signalsDescriptor       SignalsDescriptor OPTIONAL, 
        ... 
   } 
    
   EventBufferDescriptor ::= SEQUENCE OF EventSpec 
    
   EventSpec ::= SEQUENCE 
   { 
        eventName               EventName, 
        streamID                StreamID OPTIONAL, 
        eventParList    SEQUENCE OF EventParameter, 
        ... 
   } 
    
    
   SignalsDescriptor ::= SEQUENCE OF SignalRequest 
    
   SignalRequest ::=CHOICE 
   { 
        signal          Signal, 
        seqSigList              SeqSigList, 
        ... 
   } 
    
   SeqSigList ::= SEQUENCE 
   { 
        id              INTEGER(0..65535), 
        signalList      SEQUENCE OF Signal 
   } 
    
   Signal ::= SEQUENCE 
   { 
        signalName              SignalName, 
        streamID                StreamID OPTIONAL, 
        sigType                 SignalType OPTIONAL, 
        duration                INTEGER (0..65535) OPTIONAL, 
        notifyCompletion        NotifyCompletion OPTIONAL, 
        keepActive              BOOLEAN OPTIONAL, 
        sigParList              SEQUENCE OF SigParameter, 
        ... 
   } 
    
   SignalType ::= ENUMERATED 
   { 
        brief(0), 
     
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        onOff(1), 
        timeOut(2), 
        ... 
   } 
    
   SignalName ::= PkgdName 
    
   NotifyCompletion ::= BIT STRING 
   { 
        onTimeOut(0), onInterruptByEvent(1), 
        onInterruptByNewSignalDescr(2), otherReason(3) 
   } 
    
   SigParameter ::= SEQUENCE 
   { 
        sigParameterName                Name, 
        value                           Value, 
   -- For use of extraInfo see the comment related to PropertyParm 
        extraInfo CHOICE 
        { 
                relation        Relation, 
                range           BOOLEAN, 
                sublist BOOLEAN 
        } OPTIONAL, 
        ... 
   } 
    
   -- For an AuditCapReply with all events, the RequestID SHALL be ALL. 
   -- ALL is represented by 0xffffffff. 
    
   RequestID ::= INTEGER(0..4294967295)   -- 32 bit unsigned integer 
    
   ModemDescriptor ::= SEQUENCE 
   { 
        mtl     SEQUENCE OF ModemType,  
        mpl     SEQUENCE OF PropertyParm, 
        nonStandardData NonStandardData OPTIONAL 
   } 
    
   ModemType ::= ENUMERATED 
   { 
        v18(0), 
        v22(1), 
        v22bis(2), 
        v32(3), 
        v32bis(4), 
        v34(5), 
        v90(6), 
        v91(7), 
        synchISDN(8), 
        ... 
   } 
    
   DigitMapDescriptor ::= SEQUENCE 
     
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   { 
        digitMapName    DigitMapName    OPTIONAL, 
        digitMapValue   DigitMapValue   OPTIONAL 
   } 
    
   DigitMapName ::= Name 
    
   DigitMapValue ::= SEQUENCE 
   { 
        startTimer              INTEGER(0..99) OPTIONAL, 
        shortTimer              INTEGER(0..99) OPTIONAL, 
        longTimer               INTEGER(0..99) OPTIONAL, 
        digitMapBody    IA5String, 
        -- See Section A.3 for explanation of digit map syntax 
        ... 
   } 
    
   ServiceChangeParm ::= SEQUENCE 
   { 
        serviceChangeMethod     ServiceChangeMethod, 
        serviceChangeAddress    ServiceChangeAddress OPTIONAL, 
        serviceChangeVersion    INTEGER(0..99) OPTIONAL, 
        serviceChangeProfile    ServiceChangeProfile OPTIONAL, 
        serviceChangeReason     Value,  
   -- A serviceChangeReason consists of a numeric reason code 
   -- and an optional text description. 
   -- The serviceChangeReason SHALL be a string consisting of  
   -- a decimal reason code, optionally followed by a single  
   -- space character and a textual description string. 
   -- This string is first ASN.1 BER encoded as an IA5String. 
   -- The result of this ASN.1 BER encoding is then encoded as 
   -- an ASN.1 BER OCTET STRING, "double wrapping" the value 
   -- as was done for package elements. 
        serviceChangeDelay      INTEGER(0..4294967295) OPTIONAL, 
                                    -- 32 bit unsigned integer 
        serviceChangeMgcId      MId OPTIONAL, 
        timeStamp                       TimeNotation OPTIONAL, 
        nonStandardData         NonStandardData OPTIONAL, 
        ..., 
        serviceChangeInfo       AuditDescriptor OPTIONAL 
   } 
    
   ServiceChangeAddress ::= CHOICE 
   { 
        portNumber      INTEGER(0..65535), -- TCP/UDP port number 
        ip4Address      IP4Address, 
        ip6Address      IP6Address, 
        domainName      DomainName, 
        deviceName      PathName, 
        mtpAddress      OCTET STRING(SIZE(2..4)), 
        ... 
   } 
    
   ServiceChangeResParm ::= SEQUENCE 
     
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   { 
        serviceChangeMgcId      MId OPTIONAL, 
        serviceChangeAddress    ServiceChangeAddress OPTIONAL, 
        serviceChangeVersion    INTEGER(0..99) OPTIONAL, 
        serviceChangeProfile    ServiceChangeProfile OPTIONAL, 
        timestamp               TimeNotation OPTIONAL, 
        ... 
   } 
    
   ServiceChangeMethod ::= ENUMERATED 
   { 
        failover(0), 
        forced(1), 
        graceful(2), 
        restart(3), 
        disconnected(4), 
        handOff(5), 
        ... 
   } 
    
   ServiceChangeProfile ::= SEQUENCE 
   { 
        profileName     IA5String(SIZE (1..67)),         
        -- 64 for name, 1 for /, 2 for version to match ABNF 
   } 
    
   PackagesDescriptor ::= SEQUENCE OF PackagesItem 
    
   PackagesItem ::= SEQUENCE 
   { 
        packageName             Name, 
        packageVersion  INTEGER(0..99), 
        ... 
   } 
    
   StatisticsDescriptor ::= SEQUENCE OF StatisticsParameter 
    
   StatisticsParameter ::= SEQUENCE 
   { 
        statName                PkgdName, 
        statValue               Value OPTIONAL 
   } 
    
   NonStandardData ::= SEQUENCE 
   { 
        nonStandardIdentifier   NonStandardIdentifier, 
        data                            OCTET STRING 
   } 
    
   NonStandardIdentifier                ::= CHOICE 
   { 
        object                  OBJECT IDENTIFIER, 
        h221NonStandard         H221NonStandard, 
        experimental            IA5String(SIZE(8)),  
     
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    -- first two characters should be "X-" or "X+" 
        ... 
   } 
    
   H221NonStandard ::= SEQUENCE 
   {    t35CountryCode1   INTEGER(0..255), 
        t35CountryCode2   INTEGER(0..255), -- country, as per T.35 
        t35Extension      INTEGER(0..255),       -- assigned nationally 
        manufacturerCode  INTEGER(0..65535), -- assigned nationally 
        ... 
   } 
    
   TimeNotation ::= SEQUENCE 
   { 
        date            IA5String(SIZE(8)),  -- yyyymmdd format 
        time            IA5String(SIZE(8))  -- hhmmssss format 
   } 
    
   Value ::= SEQUENCE OF OCTET STRING 
    
    
   END 
    
    
A.3     Digit maps and path names 
    
   From a syntactic viewpoint, digit maps are strings with syntactic 
   restrictions imposed upon them.  The syntax of valid digit maps is 
   specified in ABNF [RFC 2234].  The syntax for digit maps presented 
   in this section is for illustrative purposes only. The definition of 
   digitMap in Annex B takes precedence in the case of differences 
   between the two. 
    
   digitMap = (digitString / LWSP "(" LWSP digitStringList LWSP ")" 
        LWSP) 
   digitStringList = digitString *( LWSP "|" LWSP digitString ) 
   digitString = 1*(digitStringElement) 
   digitStringElement = digitPosition [DOT] 
   digitPosition = digitMapLetter / digitMapRange 
   digitMapRange = ("x" / (LWSP "[" LWSP digitLetter LWSP "]" LWSP)) 
   digitLetter = *((DIGIT "-" DIGIT) /digitMapLetter) 
   digitMapLetter = DIGIT              ;digits 0-9 
                / %x41-4B / %x61-6B    ;a-k and A-K 
                / "L"   / "S"          ;Inter-event timers 
                                       ;(long, short) 
                / "Z"                  ;Long duration event 
   DOT = %x2E ; "." 
   LWSP = *(WSP / COMMENT / EOL) 
   WSP = SP / HTAB 
   COMMENT = ";" *(SafeChar / RestChar / WSP) EOL 
   EOL = (CR [LF]) / LF 
   SP = %x20 
   HTAB = %x09 
   CR = %x0D 
     
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   LF = %x0A 
   SafeChar = DIGIT / ALPHA / "+" / "-" / "&" / "!" / "_" / "/" / 
        "'" / "?" / "@" / "^" / "`" / "~" / "*" / "$" / "\" / 
        "(" / ")" / "%" / "." 
   RestChar = ";" / "[" / "]" / "{" / "}" / ":" / "," / "#" / 
                "<" / ">" / "=" / %x22 
   DIGIT = %x30-39                      ; digits 0 through 9 
   ALPHA = %x41-5A / %x61-7A    ; A-Z, a-z 
   A path name is also a string with syntactic restrictions imposed 
   upon it.  The ABNF production defining it is copied from Annex B. 
    
   ; Total length of pathNAME must not exceed 64 chars. 
   pathNAME = ["*"] NAME *("/" / "*"/ ALPHA / DIGIT /"_" / "$" )  
              ["@" pathDomainName ] 
    
   ; ABNF allows two or more consecutive "." although it is meaningless  
   ; in a path domain name.  
   pathDomainName       = (ALPHA / DIGIT / "*" )  
                          *63(ALPHA / DIGIT / "-" / "*" / ".") 
    
   NAME = ALPHA *63(ALPHA / DIGIT / "_" ) 
     
     
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ANNEX B TEXT ENCODING OF THE PROTOCOL (NORMATIVE) 
    
B.1     Coding of wildcards 
    
   In a text encoding of the protocol, while TerminationIDs are 
   arbitrary, by judicious choice of names, the wildcard character, "*" 
   may be made more useful.  When the wildcard character is 
   encountered, it will "match" all TerminationIDs having the same 
   previous and following characters (if appropriate).  For example, if 
   there were TerminationIDs of R13/3/1, R13/3/2 and R13/3/3, the 
   TerminationID R13/3/* would match all of them.  There are some 
   circumstances where ALL Terminations must be referred to.  The 
   TerminationID "*" suffices, and is referred to as ALL. The CHOOSE 
   TerminationID "$" may be used to signal to the MG that it has to 
   create an ephemeral Termination or select an idle physical 
   Termination. 
    
B.2     ABNF specification 
    
   The protocol syntax is presented in ABNF according to RFC2234. 
   Note  “ This syntax specification does not enforce all restrictions 
   on element inclusions and values.  Some additional restrictions are 
   stated in comments and other restrictions appear in the text of this 
   recommendation.  These additional restrictions are part of the 
   protocol even though not enforced by this specification. 
   Note - The syntax is context-dependent. For example, "Add" can be 
   the AddToken or a NAME depending on the context in which it occurs. 
   EVERYTHING IN THE ABNF AND TEXT ENCODING IS CASE INSENSITIVE. This 
   includes TerminationIDs, digitmap Ids etc. THE SDP IS CASE SENSITIVE 
   AS PER RFC2327. 
    
    
   ; NOTE -- The ABNF in this section uses the VALUE construct (or  
   ; lists of VALUE constructs) to encode various package element  
   ; values (properties,signal parameters, etc.).  The types of these  
   ; values vary and are specified the relevant package definition.   
   ; Several such types are described in section 12.2. 
   ; 
   ; The ABNF specification for VALUE allows a quotedString form or a 
   ; collection of SafeChars.  The encoding of package element values  
   ; into ABNF VALUES is specified below.  If a type's encoding allows  
   ; characters other than SafeChars, the quotedString form MUST be  
   ; used for all values of that type, even for specific values that  
   ; consist only of SafeChars. 
   ; 
   ; String:  A string MUST use the quotedString form of VALUE and can 
   ; contain anything allowable in the quotedString form. 
   ; 
   ; Integer, Double, and Unsigned Integer:  Decimal values can be  
   ; encoded using characters 0-9.  Hexadecimal values must be prefixed  
   ; with '0x'and can use characters 0-9,a-f,A-F.  An octal format is  
   ; not supported.Negative integers start with '-' and MUST be  
   ; Decimal.  The SafeChar form of VALUE MUST be used. 
   ;  
     
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   ; Character:  A UTF-8 encoding of a single letter surrounded by  
   ; double quotes. 
   ; 
   ; Enumeration:  An enumeration MUST use the SafeChar form of VALUE 
   ; and can contain anything allowable in the SafeChar form. 
   ; 
   ; Boolean:  Boolean values are encoded as "on" and "off" and are 
   ; case insensitive.  The SafeChar form of VALUE MUST be used. 
   ; 
   ; Future types:  Any defined types MUST fit within 
   ; the ANBF specification of VALUE.  Specifically, if a type's  
   ; encoding allows characters other than SafeChars, the quotedString  
   ; form MUST be used for all values of that type, even for specific  
   ; values that consist only of SafeChars.  
   ; 
   ; Note that there is no way to use the double quote character within 
   ; a value. 
   ; 
   ; Note that SDP disallows whitespace at the beginning of a line,  
   ; Megaco ABNF allows whitespace before the beginning of the SDP in  
   ; the Local/Remote descriptor.  Parsers should accept whitespace  
   ; between the LBRKT following the Local/Remote token and the  
   ; beginning of the SDP. 
    
   megacoMessage        = LWSP [authenticationHeader SEP ] message  
    
   authenticationHeader = AuthToken EQUAL SecurityParmIndex COLON  
                          SequenceNum COLON AuthData  
                           
   SecurityParmIndex    = "0x" 8(HEXDIG) 
   SequenceNum          = "0x" 8(HEXDIG) 
   AuthData             = "0x" 24*64(HEXDIG) 
    
   message            = MegacopToken SLASH Version SEP mId SEP 
   messageBody 
   ; The version of the protocol defined here is equal to 2. 
                         
   messageBody          = ( errorDescriptor / transactionList ) 
    
   transactionList      = 1*( transactionRequest / transactionReply /  
                          transactionPending / transactionResponseAck ) 
   ;Use of resopnse acks is dependent on underlying transport 
    
   transactionPending   = PendingToken EQUAL TransactionID LBRKT RBRKT 
    
   transactionResponseAck = ResponseAckToken LBRKT transactionAck 
                                        *(COMMA transactionAck) RBRKT 
   transactionAck = transactionID / (transactionID Ÿ-Ÿ transactionID) 
    
   transactionRequest   = TransToken EQUAL TransactionID LBRKT 
                          actionRequest *(COMMA actionRequest) RBRKT 
    
   actionRequest        = CtxToken EQUAL ContextID LBRKT (( 
                          contextRequest [COMMA  commandRequestList])  
     
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                          / commandRequestList) RBRKT 
    
   contextRequest          = ((contextProperties [COMMA contextAudit]) 
                           / contextAudit) 
    
   contextProperties    = contextProperty *(COMMA contextProperty) 
    
   ; at-most-once 
   contextProperty      = (topologyDescriptor / priority / 
   EmergencyToken / contextAttrDescriptor / packagesDescriptor) 
    
   contextAudit    = ContextAuditToken LBRKT  
                          contextAuditProperties *(COMMA  
                          contextAuditProperties) RBRKT 
    
   ; at-most-once 
   contextAuditProperties = ( TopologyToken / EmergencyToken /  
                              PriorityToken /  
   IndAudcontextAttrDescriptor ContextAttrDescriptorCapAud/ 
   IndAudContextAttrCap / ContextAttrPackages) 
   IndAudcontextAttrDescriptor 
                         = ContextAudValToken LBRKT pkgdName RBRKT 
   IndAudContextAttrCap  = ContextAudCapToken LBRKT pkgdName RBRKT 
   ContextAttrPackages   = PackagesToken 
   ContextAttrDescriptorCapAud = ContextAudDescriptorToken 
    
   ; "O-" indicates an optional command 
   ; "W-" indicates an wildcarded response to a command  
   commandRequestList= ["O-"] ["W-"] commandRequest * 
                                  (COMMA ["O-"] ["W-"]commandRequest) 
    
   commandRequest     = ( ammRequest / subtractRequest / auditRequest /  
                           notifyRequest / serviceChangeRequest)  
    
   transactionReply     = ReplyToken EQUAL TransactionID LBRKT  
                           [ ImmAckRequiredToken COMMA]                       
                           ( errorDescriptor / actionReplyList ) RBRKT  
                           
   actionReplyList      = actionReply *(COMMA actionReply )  
    
   actionReply          = CtxToken EQUAL ContextID LBRKT  
                          ( errorDescriptor / commandReply ) RBRKT 
    
   commandReply     = (( contextProperties [COMMA commandReplyList] ) /  
                           commandReplyList ) 
    
    
   commandReplyList     = commandReplys *(COMMA commandReplys ) 
    
   commandReplys      = (serviceChangeReply / auditReply / ammsReply /  
                           notifyReply ) 
    
   ;Add Move and Modify have the same request parameters 
   ammRequest           = (AddToken / MoveToken / ModifyToken ) EQUAL  
     
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                          TerminationID [LBRKT ammParameter *(COMMA  
                          ammParameter) RBRKT] 
    
   ;at-most-once 
   ammParameter         = (mediaDescriptor / modemDescriptor /  
                           muxDescriptor / eventsDescriptor /  
                           signalsDescriptor / digitMapDescriptor / 
                           eventBufferDescriptor / auditDescriptor) 
    
   ammsReply            = (AddToken / MoveToken / ModifyToken /  
                           SubtractToken ) EQUAL TerminationID [ LBRKT  
                           terminationAudit RBRKT ] 
                            
   subtractRequest      =  SubtractToken EQUAL TerminationID  
                           [ LBRKT auditDescriptor RBRKT] 
    
   auditRequest         = (AuditValueToken / AuditCapToken )EQUAL 
                           TerminationID LBRKT auditDescriptor RBRKT 
    
   auditReply           = (AuditValueToken / AuditCapToken )  
                          ( contextTerminationAudit  / auditOther)  
    
   auditOther           = EQUAL TerminationID [LBRKT  
                          terminationAudit RBRKT] 
    
   terminationAudit = auditReturnParameter *(COMMA 
                        auditReturnParameter)  
    
   contextTerminationAudit = EQUAL CtxToken ( terminationIDList /  
                          LBRKT errorDescriptor RBRKT ) 
    
   auditReturnParameter = (mediaDescriptor / modemDescriptor /   
                           muxDescriptor / eventsDescriptor /  
                           signalsDescriptor / digitMapDescriptor /  
                           observedEventsDescriptor /  
                           eventBufferDescriptor / 
                           statisticsDescriptor / packagesDescriptor /  
                           errorDescriptor / auditItem) 
    
   auditDescriptor      = AuditToken LBRKT [ auditItem  
                          *(COMMA auditItem) ] RBRKT 
    
   notifyRequest        = NotifyToken EQUAL TerminationID  
                          LBRKT ( observedEventsDescriptor  
                                [ COMMA errorDescriptor ] ) RBRKT 
    
   notifyReply          = NotifyToken EQUAL TerminationID  
                          [ LBRKT errorDescriptor RBRKT ] 
    
   serviceChangeRequest = ServiceChangeToken EQUAL TerminationID 
                          LBRKT serviceChangeDescriptor RBRKT  
    
   serviceChangeReply   = ServiceChangeToken EQUAL TerminationID 
                          [LBRKT (errorDescriptor /  
     
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                          serviceChangeReplyDescriptor) RBRKT] 
                           
   errorDescriptor   = ErrorToken EQUAL ErrorCode 
                       LBRKT [quotedString] RBRKT 
    
   ErrorCode            = 1*4(DIGIT) ; could be extended 
    
   TransactionID        = UINT32 
    
   mId                  = (( domainAddress / domainName )  
                          [":" portNumber]) / mtpAddress / deviceName 
    
   ; ABNF allows two or more consecutive "." although it is meaningless  
   ; in a domain name.  
   domainName           = "<" (ALPHA / DIGIT) *63(ALPHA / DIGIT / "-" /  
                          ".") ">" 
   deviceName           = pathNAME 
    
   ;The values 0x0, 0xFFFFFFFE and 0xFFFFFFFF are reserved. 
   ContextID            = (UINT32 / "*" / "-" / "$") 
    
   domainAddress        = "[" (IPv4address / IPv6address) "]" 
   ;RFC2373 contains the definition of IP6Addresses. 
   IPv6address          = hexpart [ ":" IPv4address ] 
   IPv4address          = V4hex DOT V4hex DOT V4hex DOT V4hex 
   V4hex                = 1*3(DIGIT) ; "0".."255" 
   ; this production, while occurring in RFC2373, is not referenced 
   ; IPv6prefix           = hexpart SLASH 1*2DIGIT 
   hexpart          = hexseq "::" [ hexseq ] / "::" [ hexseq ] / hexseq 
   hexseq               = hex4 *( ":" hex4) 
   hex4                 = 1*4HEXDIG 
    
   portNumber           = UINT16 
    
   ; Addressing structure of mtpAddress: 
   ; 25 - 15            0 
   ;    |  PC        | NI | 
   ;    24 - 14 bits    2 bits 
   ; Note: 14 bits is defined for international use. 
   ; Two national options exist where the point code is 16 or 24 bits. 
   ; To octet align the mtpAddress the MSBs shall be encoded as 0s.  
   ; An octet shall be represented by 2 hex digits. 
    
   mtpAddress           = MTPToken LBRKT 4*8 (HEXDIG) RBRKT 
    
   terminationIDList    = LBRKT TerminationID *(COMMA TerminationID) 
   RBRKT 
    
   ; Total length of pathNAME must not exceed 64 chars. 
   pathNAME        = ["*"] NAME *("/" / "*"/ ALPHA / DIGIT /"_" / "$" )  
                          ["@" pathDomainName ] 
    
   ; ABNF allows two or more consecutive "." although it is meaningless  
   ; in a path domain name.  
     
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   pathDomainName       = (ALPHA / DIGIT / "*" )  
                          *63(ALPHA / DIGIT / "-" / "*" / ".") 
                           
   TerminationID        = "ROOT" / pathNAME / "$" / "*" 
    
   mediaDescriptor = MediaToken LBRKT mediaParm *(COMMA mediaParm)  
                        RBRKT 
    
   ; at-most-once per item 
   ; using either streamParms or streamDescriptors but not both 
   mediaParm            = (streamParm / streamDescriptor /  
                           terminationStateDescriptor) 
    
   ; at-most-once 
   streamParm           = ( localDescriptor / remoteDescriptor /  
                           localControlDescriptor ) 
    
   streamDescriptor     = StreamToken EQUAL StreamID LBRKT streamParm  
                          *(COMMA streamParm) RBRKT 
    
   localControlDescriptor = LocalControlToken LBRKT localParm  
                            *(COMMA localParm) RBRKT 
    
   ; at-most-once per item except for propertyParm 
   localParm          = ( streamMode / propertyParm / reservedValueMode 
                            / reservedGroupMode ) 
    
   reservedValueMode       = ReservedValueToken EQUAL ( "ON" / "OFF" ) 
   reservedGroupMode       = ReservedGroupToken EQUAL ( "ON" / "OFF" ) 
    
   streamMode           = ModeToken EQUAL streamModes 
    
   streamModes          = (SendonlyToken / RecvonlyToken / 
   SendrecvToken /  
                          InactiveToken / LoopbackToken ) 
    
   propertyParm         = pkgdName parmValue 
   parmValue            = (EQUAL alternativeValue/ INEQUAL VALUE) 
   alternativeValue     = ( VALUE  
                                / LSBRKT VALUE *(COMMA VALUE) RSBRKT  
                            ; sublist (i.e. A AND B AND ...) 
                                / LBRKT VALUE *(COMMA VALUE) RBRKT 
                                 ; alternatives (i.e. A OR B OR ...) 
      
                                /  LSBRKT VALUE COLON VALUE RSBRKT ) 
                                 ; range 
                          
    
   INEQUAL              = LWSP (">" / "<" / "#" ) LWSP 
   LSBRKT               = LWSP "[" LWSP 
   RSBRKT               = LWSP "]" LWSP 
    
   ; Note “ The octet zero is not among the permitted characters in 
   octet string. As the current definition is 
     
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   ; limited to SDP, and a zero octet would not be a legal character in 
   SDP, this is not a concern. 
   localDescriptor      = LocalToken LBRKT octetString RBRKT 
    
   remoteDescriptor     = RemoteToken LBRKT octetString RBRKT 
    
   eventBufferDescriptor= EventBufferToken [ LBRKT eventSpec 
                          *( COMMA eventSpec) RBRKT ]  
    
   eventSpec            = pkgdName [ LBRKT eventSpecParameter 
                            *(COMMA eventSpecParameter) RBRKT ] 
   eventSpecParameter   = (eventStream / eventOther) 
    
   eventBufferControl     = BufferToken EQUAL ( "OFF" / LockStepToken ) 
    
   terminationStateDescriptor = TerminationStateToken LBRKT  
             terminationStateParm *( COMMA terminationStateParm ) RBRKT 
    
   ; at-most-once per item except for propertyParm 
   terminationStateParm =(propertyParm / serviceStates /  
                                eventBufferControl ) 
    
   serviceStates        = ServiceStatesToken EQUAL ( TestToken / 
                          OutOfSvcToken / InSvcToken ) 
    
   muxDescriptor        = MuxToken EQUAL MuxType  terminationIDList 
    
   MuxType             = ( H221Token / H223Token / H226Token / V76Token 
                           / extensionParameter ) 
    
   StreamID             = UINT16 
   pkgdName    = (PackageName SLASH ItemID) ;specific item 
                    / (PackageName SLASH "*") ;all items in package 
                    / ("*" SLASH "*") ; all items supported by the MG 
   PackageName          = NAME 
   ItemID               = NAME 
    
   eventsDescriptor  = EventsToken [ EQUAL RequestID LBRKT  
                       requestedEvent *( COMMA requestedEvent ) RBRKT ] 
    
   requestedEvent       = pkgdName [ LBRKT eventParameter 
                          *( COMMA eventParameter ) RBRKT ] 
    
   ; at-most-once each of KeepActiveToken , eventDM and eventStream 
   ;at most one of either embedWithSig or embedNoSig but not both 
   ;KeepActiveToken and embedWithSig must not both be present 
   eventParameter    = ( embedWithSig / embedNoSig / KeepActiveToken  
                        /eventDM / eventStream / eventOther ) 
    
   embedWithSig      = EmbedToken LBRKT signalsDescriptor 
                        [COMMA embedFirst ] RBRKT 
   embedNoSig        = EmbedToken LBRKT embedFirst RBRKT 
    
   ; at-most-once of each 
     
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   embedFirst = EventsToken [ EQUAL RequestID LBRKT 
             secondRequestedEvent *(COMMA secondRequestedEvent) RBRKT ] 
    
   secondRequestedEvent = pkgdName [ LBRKT secondEventParameter 
                          *( COMMA secondEventParameter ) RBRKT ] 
    
   ; at-most-once each of embedSig , KeepActiveToken, eventDM or 
   ; eventStream 
   ; KeepActiveToken and embedSig must not both be present 
   secondEventParameter = ( embedSig / KeepActiveToken / eventDM /  
                            eventStream / eventOther ) 
    
   embedSig  = EmbedToken LBRKT signalsDescriptor RBRKT 
    
   eventStream          = StreamToken EQUAL StreamID 
    
   eventOther           = eventParameterName parmValue 
    
   eventParameterName   = NAME 
    
   eventDM              = DigitMapToken EQUAL(( digitMapName ) /  
                          (LBRKT digitMapValue RBRKT ))  
    
   signalsDescriptor    = SignalsToken LBRKT [ signalParm  
                          *(COMMA signalParm)] RBRKT 
    
   signalParm           = signalList / signalRequest 
    
   signalRequest        = signalName [ LBRKT sigParameter  
                          *(COMMA sigParameter) RBRKT ] 
    
   signalList           = SignalListToken EQUAL signalListId LBRKT  
                          signalListParm *(COMMA signalListParm) RBRKT 
                           
   signalListId         = UINT16 
    
   ;exactly once signalType, at most once duration and every signal 
   ;parameter 
   signalListParm       = signalRequest 
    
   signalName           = pkgdName 
   ;at-most-once sigStream, at-most-once sigSignalType, 
   ;at-most-once sigDuration, every signalParameterName at most once 
   sigParameter  = sigStream / sigSignalType / sigDuration / sigOther 
                   / notifyCompletion / KeepActiveToken 
   sigStream            = StreamToken EQUAL StreamID 
   sigOther             = sigParameterName parmValue 
   sigParameterName     = NAME 
   sigSignalType        = SignalTypeToken EQUAL signalType 
   signalType           = (OnOffToken / TimeOutToken / BriefToken) 
   sigDuration          = DurationToken EQUAL UINT16 
   notifyCompletion     = NotifyCompletionToken EQUAL (LBRKT 
                 notificationReason *(COMMA notificationReason) RBRKT) 
    
     
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   notificationReason   = ( TimeOutToken / InterruptByEventToken 
                                / InterruptByNewSignalsDescrToken 
                                / OtherReasonToken ) 
    
   observedEventsDescriptor = ObservedEventsToken EQUAL RequestID 
                      LBRKT observedEvent *(COMMA observedEvent) RBRKT 
    
   ;time per event, because it might be buffered 
   observedEvent        = [ TimeStamp LWSP COLON] LWSP  
                          pkgdName [ LBRKT observedEventParameter 
                          *(COMMA observedEventParameter) RBRKT ] 
    
   ;at-most-once eventStream, every eventParameterName at most once 
   observedEventParameter = eventStream / eventOther 
    
   ; For an AuditCapReply with all events, the RequestID should be ALL. 
   RequestID            = ( UINT32 / "*" ) 
    
   modemDescriptor      = ModemToken (( EQUAL modemType) /  
                          (LSBRKT modemType *(COMMA modemType) RSBRKT)) 
                          [ LBRKT propertyParm  
                         *(COMMA propertyParm) RBRKT ]  
    
   ; at-most-once except for extensionParameter 
   modemType            = (V32bisToken / V22bisToken / V18Token /  
                           V22Token / V32Token / V34Token / V90Token /  
                        V91Token / SynchISDNToken / extensionParameter) 
    
   digitMapDescriptor   = DigitMapToken EQUAL  
                          ( ( LBRKT digitMapValue RBRKT ) 
                       / (digitMapName [ LBRKT digitMapValue RBRKT ]) ) 
   digitMapName       = NAME 
   digitMapValue      = ["T" COLON Timer COMMA] ["S" COLON Timer COMMA] 
                          ["L" COLON Timer COMMA]     
   digitMap  
   Timer                = 1*2DIGIT 
   digitMap = (digitString / LWSP "(" LWSP digitStringList LWSP ")" 
                LWSP) 
   digitStringList      = digitString *( LWSP "|" LWSP digitString ) 
   digitString          = 1*(digitStringElement) 
   digitStringElement   = digitPosition [DOT] 
   digitPosition        = digitMapLetter / digitMapRange 
   digitMapRange    = ("x" / (LWSP "[" LWSP digitLetter LWSP "]" LWSP)) 
   digitLetter          = *((DIGIT "-" DIGIT ) / digitMapLetter) 
   digitMapLetter       = DIGIT   ;Basic event symbols 
                 / %x41-4B / %x61-6B ; a-k, A-K 
                 / "L" / "S"   ;Inter-event timers (long, short) 
                 / "Z"         ;Long duration modifier 
    
   ;at-most-once, and DigitMapToken and PackagesToken are not allowed 
   ;in AuditCapabilities command 
   auditItem            = ( MuxToken / ModemToken / MediaToken /  
                           SignalsToken / EventBufferToken / 
                           DigitMapToken / StatsToken / EventsToken / 
     
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                           ObservedEventsToken / PackagesToken / 
                           indAudterminationAudit) 
    
   indAudterminationAudit   = indAudauditReturnParameter  
                                *(COMMA indAudauditReturnParameter)  
    
   indAudauditReturnParameter = (indAudmediaDescriptor /  
                                indAudmodemDescriptor /   
                                indAudmuxDescriptor /  
                                indAudeventsDescriptor /  
                                indAudsignalsDescriptor /  
                                indAuddigitMapDescriptor /  
                                indAudeventBufferDescriptor / 
                                indAudstatisticsDescriptor /  
                                indAudpackagesDescriptor) 
    
    
   indAudmediaDescriptor   = MediaToken LBRKT indAudmediaParm RBRKT 
    
   ; at-most-once per item 
   ; and either streamParm or streamDescriptor but not both 
   indAudmediaParm            = (indAudstreamParm /      
                                indAudstreamDescriptor /                         
                                indAudterminationStateDescriptor) 
    
   ; at-most-once 
   indAudstreamParm           = ( indAudlocalDescriptor / 
                                 indAudremoteDescriptor /  
                                 indAudlocalControlDescriptor ) 
    
   indAudstreamDescriptor     = StreamToken EQUAL StreamID  
                                LBRKT indAudstreamParmRBRKT 
    
   indAudlocalControlDescriptor = LocalControlToken LBRKT  
                                        indAudlocalParm RBRKT 
    
   ; at-most-once per item 
   indAudlocalParm            = ( ModeToken / pkgdName / 
                                ReservedValueToken / 
                                ReservedGroupToken ) 
    
   ; to audit groups a v= line should separate the SDP. Property values 
   ; shall be set to "?" 
   indAudlocalDescriptor      = LocalToken LBRKT octetString RBRKT 
   indAudremoteDescriptor     = RemoteToken LBRKT octetString RBRKT 
    
   indAudterminationStateDescriptor = TerminationStateToken LBRKT  
                                indAudterminationStateParm RBRKT 
    
   ; at-most-once per item 
   indAudterminationStateParm =(pkgdName / ServiceStatesToken / 
                                BufferToken) 
    
   indAudeventBufferDescriptor= EventBufferToken LBRKT indAudeventSpec 
     
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                                RBRKT  
    
   indAudeventSpec = pkgdName [ LBRKT indAudeventSpecParameter RBRKT ] 
   indAudeventSpecParameter   = (eventStream / eventParameterName) 
    
   indAudeventsDescriptor     = EventsToken EQUAL RequestID LBRKT  
                                        indAudrequestedEvent RBRKT 
    
   indAudrequestedEvent       = pkgdName 
    
   indAudsignalsDescriptor    = SignalsToken LBRKT [ indAudsignalParm ] 
                                RBRKT 
    
   indAudsignalParm           = indAudsignalList / indAudsignalRequest 
    
   indAudsignalRequest        = signalName 
   indAudsignalList = SignalListToken EQUAL signalListId LBRKT  
                      indAudsignalListParm RBRKT 
    
   indAudmodemDescriptor      = ModemToken ( EQUAL modemType ) 
    
   indAuddigitMapDescriptor   = DigitMapToken EQUAL (digitMapName ) 
    
   indAudstatisticsDescriptor = StatsToken LBRKT pkgdName RBRKT 
    
   indAudpackagesDescriptor   = PackagesToken LBRKT packagesItem RBRKT 
    
    
   serviceChangeDescriptor = ServicesToken LBRKT serviceChangeParm  
                            *(COMMA serviceChangeParm) RBRKT 
    
   ;at most one of either serviceChangeAddress or serviceChangeMgcId 
   ; but not both 
   ;serviceChangeMethod and serviceChangeReason are REQUIRED 
   serviceChangeParm    = (serviceChangeMethod / serviceChangeReason / 
                          serviceChangeDelay / serviceChangeAddress /   
                         serviceChangeProfile / extension / TimeStamp / 
                          serviceChangeMgcId / serviceChangeVersion / 
                         auditItem) 
                         
   serviceChangeReplyDescriptor = ServicesToken LBRKT 
                       servChgReplyParm *(COMMA servChgReplyParm) RBRKT 
    
   ;at-most-once. Version is REQUIRED on first ServiceChange response 
   ;at most one of either serviceChangeAddress or serviceChangeMgcId 
   ; but not both 
   servChgReplyParm     = (serviceChangeAddress / serviceChangeMgcId / 
                          serviceChangeProfile / serviceChangeVersion /     
                          TimeStamp) 
   serviceChangeMethod  = MethodToken EQUAL (FailoverToken /  
                          ForcedToken / GracefulToken / RestartToken /  
                          DisconnectedToken / HandOffToken /  
                          extensionParameter)  
   ; A serviceChangeReason consists of a numeric reason code 
     
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   ; and an optional text description. 
   ; A serviceChangeReason MUST be encoded using the quotedString  
   ; form of VALUE. 
   ; The quotedString SHALL contain a decimal reason code, 
   ; optionally followed by a single space character and a  
   ; textual description string. 
   serviceChangeReason  = ReasonToken  EQUAL VALUE 
   serviceChangeDelay   = DelayToken   EQUAL UINT32 
   serviceChangeAddress = ServiceChangeAddressToken EQUAL ( mId /  
                             portNumber ) 
   serviceChangeMgcId   = MgcIdToken   EQUAL mId 
   serviceChangeProfile = ProfileToken EQUAL NAME SLASH Version 
   serviceChangeVersion = VersionToken EQUAL Version 
   extension            = extensionParameter parmValue 
    
   packagesDescriptor   = PackagesToken LBRKT packagesItem   
                          *(COMMA packagesItem) RBRKT 
    
   Version              = 1*2(DIGIT) 
   packagesItem         = NAME "-" UINT16 
    
   TimeStamp            = Date "T" Time ; per ISO 8601:1988  
   ; Date = yyyymmdd 
   Date                 = 8(DIGIT) 
   ; Time = hhmmssss 
   Time                 = 8(DIGIT) 
   statisticsDescriptor = StatsToken LBRKT statisticsParameter 
                         *(COMMA statisticsParameter ) RBRKT 
    
   ;at-most-once per item  
   statisticsParameter  = pkgdName [EQUAL VALUE]  
    
   topologyDescriptor   = TopologyToken LBRKT topologyTriple 
                                *(COMMA topologyTriple) RBRKT 
   topologyTriple = terminationA COMMA terminationB COMMA  
                                topologyDirection [COMMA eventStream ] 
   terminationA         = TerminationID 
   terminationB         = TerminationID 
   topologyDirection    = BothwayToken / IsolateToken / OnewayToken 
    
   contextAttrDescriptor   = ContextAttrToken LBRKT propertyParm 
                                 *(COMMA propertyParm) RBRKT 
    
   priority             = PriorityToken EQUAL UINT16 
    
   extensionParameter   = "X"  ("-" / "+") 1*6(ALPHA / DIGIT) 
    
   ; octetString is used to describe SDP defined in RFC2327. 
   ; Caution should be taken if CRLF in RFC2327 is used. 
   ; To be safe, use EOL in this ABNF. 
   ; Whenever "}" appears in SDP, it is escaped by "\", e.g., "\}" 
   octetString          = *(nonEscapeChar) 
   nonEscapeChar        = ( "\}" / %x01-7C / %x7E-FF ) 
   ;Note “ The double-quote character is not allowed in quotedString. 
     
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   quotedString         = DQUOTE *(SafeChar / RestChar/ WSP) DQUOTE 
    
   UINT16               = 1*5(DIGIT)  ; %x0-FFFF  
   UINT32               = 1*10(DIGIT) ; %x0-FFFFFFFF  
    
   NAME                 = ALPHA *63(ALPHA / DIGIT / "_" ) 
   VALUE                = quotedString / 1*(SafeChar) 
   SafeChar             = DIGIT / ALPHA / "+" / "-" / "&" /  
                          "!" / "_" / "/" / "'" / "?" / "@" /  
                          "^" / "`" / "~" / "*" / "$" / "\" /  
                          "(" / ")" / "%" / "|" / "." 
    
   EQUAL                = LWSP %x3D LWSP ; "=" 
   COLON                = %x3A           ; ":" 
   LBRKT                = LWSP %x7B LWSP ; "{" 
   RBRKT                = LWSP %x7D LWSP ; "}" 
   COMMA                = LWSP %x2C LWSP ; "," 
   DOT                  = %x2E           ; "." 
   SLASH                = %x2F           ; "/" 
   ALPHA                = %x41-5A / %x61-7A ; A-Z / a-z 
   DIGIT                = %x30-39         ; 0-9 
   DQUOTE               = %x22            ; " (Double Quote) 
   HEXDIG               = ( DIGIT / "A" / "B" / "C" / "D" / "E" / "F" ) 
   SP                   = %x20        ; space 
   HTAB                 = %x09        ; horizontal tab 
   CR                   = %x0D        ; Carriage return 
   LF                   = %x0A        ; linefeed 
   LWSP                 = *( WSP / COMMENT / EOL ) 
   EOL                  = (CR [LF] / LF ) 
   WSP                  = SP / HTAB ; white space 
   SEP                  = ( WSP / EOL / COMMENT) LWSP 
   COMMENT              = ";" *(SafeChar/ RestChar / WSP / %x22) EOL 
   RestChar           = ";" / "[" / "]" / "{" / "}" / ":" / "," / "#" /  
                          "<" / ">" / "="  
    
    
    
   ; New Tokens added to sigParameter must take the format of SPA* 
   ; * may be of any form ie. SPAM 
   ; New Tokens added to eventParameter must take the form of EPA* 
   ; * may be of any form ie. EPAD 
    
   AddToken                   = ("Add"                   / "A") 
   AuditToken                 = ("Audit"                 / "AT") 
   AuditCapToken              = ("AuditCapability"       / "AC") 
   AuditValueToken            = ("AuditValue"            / "AV") 
   AuthToken                  = ("Authentication"        / "AU") 
   BothwayToken               = ("Bothway"               / "BW") 
   BriefToken                 = ("Brief"                 / "BR") 
   BufferToken                = ("Buffer"                / "BF") 
   CtxToken                   = ("Context"               / "C") 
   ContextAttrToken           = ("ContextAttr"           / "CT") 
   ContextAudCapToken         = ("ContextAudCap"         / "CC") 
   ContextAudDescriptorToken  = ("ContextAudDes"         / "CD") 
     
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   ContextAuditToken          = ("ContextAudit"          / "CA") 
    
   ContextAudValToken         = ("ContextAudVal"         / "CV") 
   DigitMapToken              = ("DigitMap"              / "DM") 
   DisconnectedToken          = ("Disconnected"          / "DC") 
   DelayToken                 = ("Delay"                 / "DL") 
   DurationToken              = ("Duration"              / "DR") 
   EmbedToken                 = ("Embed"                 / "EM") 
   EmergencyToken             = ("Emergency"             / "EG") 
   ErrorToken                 = ("Error"                 / "ER") 
   EventBufferToken           = ("EventBuffer"           / "EB") 
   EventsToken                = ("Events"                / "E") 
   FailoverToken              = ("Failover"              / "FL") 
   ForcedToken                = ("Forced"                / "FO") 
   GracefulToken              = ("Graceful"              / "GR") 
   H221Token                  = ("H221" ) 
   H223Token                  = ("H223" ) 
   H226Token                  = ("H226" ) 
   HandOffToken               = ("HandOff"               / "HO") 
   ImmAckRequiredToken        = ("ImmAckRequired"        / "IA") 
   InactiveToken              = ("Inactive"              / "IN") 
   IsolateToken               = ("Isolate"               / "IS") 
   InSvcToken                 = ("InService"             / "IV") 
   InterruptByEventToken      = ("IntByEvent"            / "IBE") 
   InterruptByNewSignalsDescrToken 
                              = ("IntBySigDescr"         / "IBS") 
   KeepActiveToken            = ("KeepActive"            / "KA") 
   LocalToken                 = ("Local"                 / "L") 
   LocalControlToken          = ("LocalControl"          / "O") 
   LockStepToken              = ("LockStep"              / "SP") 
   LoopbackToken              = ("Loopback"              / "LB") 
   MediaToken                 = ("Media"                 / "M") 
   MegacopToken               = ("MEGACO"                / "!") 
   MethodToken                = ("Method"                / "MT") 
   MgcIdToken                 = ("MgcIdToTry"            / "MG") 
   ModeToken                  = ("Mode"                  / "MO") 
   ModifyToken                = ("Modify"                / "MF") 
   ModemToken                 = ("Modem"                 / "MD") 
   MoveToken                  = ("Move"                  / "MV") 
   MTPToken                   = ("MTP") 
   MuxToken                   = ("Mux"                   / "MX") 
   NotifyToken                = ("Notify"                / "N") 
   NotifyCompletionToken      = ("NotifyCompletion"      / "NC") 
   ObservedEventsToken        = ("ObservedEvents"        / "OE") 
   OnewayToken                = ("Oneway"                / "OW") 
   OnOffToken                 = ("OnOff"                 / "OO") 
   OtherReasonToken           = ("OtherReason"           / "OR") 
   OutOfSvcToken              = ("OutOfService"          / "OS") 
   PackagesToken              = ("Packages"              / "PG") 
   PendingToken               = ("Pending"               / "PN") 
   PriorityToken              = ("Priority"              / "PR") 
   ProfileToken               = ("Profile"               / "PF") 
   ReasonToken                = ("Reason"                / "RE") 
   RecvonlyToken              = ("ReceiveOnly"           / "RC") 
     
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   ReplyToken                 = ("Reply"                 / "P") 
   RestartToken               = ("Restart"               / "RS") 
   RemoteToken                = ("Remote"                / "R") 
   ReservedGroupToken         = ("ReservedGroup"         / "RG") 
   ReservedValueToken         = ("ReservedValue"         / "RV") 
   SendonlyToken              = ("SendOnly"              / "SO") 
   SendrecvToken              = ("SendReceive"           / "SR") 
   ServicesToken              = ("Services"              / "SV") 
   ServiceStatesToken         = ("ServiceStates"         / "SI") 
   ServiceChangeToken         = ("ServiceChange"         / "SC") 
   ServiceChangeAddressToken  = ("ServiceChangeAddress"  / "AD") 
   SignalListToken            = ("SignalList"            / "SL") 
   SignalsToken               = ("Signals"               / "SG") 
   SignalTypeToken            = ("SignalType"            / "SY") 
   StatsToken                 = ("Statistics"            / "SA") 
   StreamToken                = ("Stream"                / "ST") 
   SubtractToken              = ("Subtract"              / "S") 
   SynchISDNToken             = ("SynchISDN"             / "SN") 
   TerminationStateToken      = ("TerminationState"      / "TS") 
   TestToken                  = ("Test"                  / "TE") 
   TimeOutToken               = ("TimeOut"               / "TO") 
   TopologyToken              = ("Topology"              / "TP") 
   TransToken                 = ("Transaction"           / "T") 
   ResponseAckToken           = ("TransactionResponseAck" / "K") 
   V18Token                   = ("V18") 
   V22Token                   = ("V22") 
   V22bisToken                = ("V22b") 
   V32Token                   = ("V32") 
   V32bisToken                = ("V32b") 
   V34Token                   = ("V34") 
   V76Token                   = ("V76") 
   V90Token                   = ("V90") 
   V91Token                   = ("V91") 
   VersionToken               = ("Version"               /   "V") 
    
B.3     Hexadecimal octet coding 
    
   Hexadecimal octet coding is a means for representing a string of 
   octets as a string of hexadecimal digits, with two digits 
   representing each octet. This octet encoding should be used when 
   encoding octet strings in the text version of the protocol. 
    
   For each octet, the 8-bit sequence is encoded as two hexadecimal 
   digits. Bit 0 is the first transmitted; bit 7 is the last. 
    
   Bits 7-4 are encoded as the first hexadecimal digit, with Bit 7 as 
   MSB and Bit 4 as LSB. Bits 3-0 are encoded as the second hexadecimal 
   digit, with Bit 3 as MSB and Bit 0 as LSB. 
    
     
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   Examples: 
    
   Octet bit pattern                   Hexadecimal coding 
   00011011                            D8 
   11100100                            27 
   10000011 10100010 11001000 00001001 C1451390 
    
B.4     Hexadecimal octet sequence 
    
   A hexadecimal octet sequence is an even number of hexadecimal 
   digits, terminated by a <CR> character.   
    
     
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ANNEX C TAGS FOR MEDIA STREAM PROPERTIES (NORMATIVE) 
    
   Parameters for Local, Remote and LocalControl descriptors are 
   specified as tag-value pairs if binary encoding is used for the 
   protocol.  This annex contains the property names (PropertyID), the 
   tags (Property Tag), type of the property (Type) and the values 
   (Value).Values presented in the Value field when the field contains 
   references shall be regarded as "information". The reference 
   contains the normative values.  If a value field does not contain a 
   reference then the values in that field can be considered as 
   "normative". 
    
   Tags are given as hexadecimal numbers in this annex. When setting 
   the value of a property, a MGC may underspecify the value according 
   to one of the mechanisms specified in section 7.1.1. 
    
   It is optional to support the properties in this Annex or any of its 
   sub-sections. For example 3 properties from C.3 and five properties 
   from C.8 may be implemented only. 
    
   For type "enumeration" the value is represented by the value in 
   brackets, e.g., Send(0), Receive(1). Annex C properties with the 
   types "N bits" or "M Octets" should be treated as Octet Strings when 
   encoding the protocol. Properties with "N bit integer" shall be 
   treated as an integers. "String" shall be treated as an IA5String 
   when encoding the protocol. 
    
   When a type is smaller than one octet, the value shall be stored in 
   the low-order bits of an octet string of size 1.   
    
C.1     General Media Attributes 
    
   PropertyID   PropertyTag    Type         Value 
                                              
   Media        1001           Enumeration  Audio(0), Video(1) 
                                             ,Data(2), 
                                               
   Transmission 1002           Enumeration  Send(0), Receive(1), 
   mode                                      Send&Receive(2) 
                                              
   Number of    1003           Unsigned     0-255 
   Channels                     Integer 
                                 
   Sampling     1004           Unsigned     0-2^32 
   rate                         Integer 
                                 
   Bitrate      1005           Integer      (0..4294967295)Note “ 
                                             units of 100 bit/s 
                                              
   ACodec       1006           Octet        Audio Codec 
                                String       Type:Reference: ITU-T Rec. 
                                             Q.765.5 Non-ITU codecs are 
                                             defined with the 
     
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                                             appropriate standards 
                                             organisation under a 
                                             defined Organizational 
                                             Identitifier. 
                                              
   Samplepp     1007           Unsigned     Maximum samples or frames 
                                Integer      per packet: 0-65535 
                                              
   Silencesupp  1008           BOOLEAN      Silence Suppression: 
                                             True/false 
                                              
   Encrypttype  1009           Octet        Ref.: rec. H.245 
                                string 
                                 
   Encryptkey   100A           Octet        Encryption key 
                                string       Ref.: rec. H.235 
                                SIZE(0..655
                                35) 
   Echocanc     100B                        Not Used. See H.248 E.13 
                                             for an example of possible 
                                             Echo Control properties. 
                                              
   Gain         100C           Unsigned     Gain in db: 0-65535 
                                Integer 
                                 
   Jitterbuff   100D           Unsigned     Jitter buffer size in ms: 
                                Integer      0-65535 
                                              
   PropDelay    100E           Unsigned     Propagation Delay: 
                                Integer      0..65535 
                                             Maximum propagation delay 
                                             in milliseconds for the 
                                             bearer connection between 
                                             two  media gateways. The 
                                             maximum delay will be 
                                             dependent on the bearer 
                                             technology. 
                                              
   RTPpayload   100F           integer      Payload type in RTP 
                                             Profile for Audio and 
                                             Video Conferences with 
                                             Minimal Control 
                                             Ref.: RFC 1890 
    
    
    
     
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C.2     Mux Properties 
    
   PropertyID PropertyTag    Type    Value 
                                       
   H.221      2001           Octet   Ref.: rec. H.245, 
                              string  H222LogicalChannelParameters 
                                       
   H223       2002           Octet   Ref.: rec. H.245, 
                              string  H223LogicalChannelParameters 
                                       
   V76        2003           Octet   Ref.: rec. H.245, 
                              String  V76LogicalChannelParameters 
                                       
   H2250      2004           Octet   Ref.: rec. H.245, 
                              String  H2250LogicalChannelParameters 
    
    
C.3     General bearer properties 
    
   PropertyID PropertyTag Type        Value 
                                        
   Mediatx    3001        Enumeration Media Transport Type:  
                                       TDM Circuit(0), ATM(1), FR(2), 
                                       Ipv4(3), Ipv6(4), € 
                                        
   BIR        3002        4 OCTET     Value depends on transport 
                                       technology 
                                        
   NSAP       3003        1-20 OCTETS See NSAP 
                                       Reference: ITU X.213 Annex A 
    
    
C.4     General ATM properties 
    
   PropertyID PropertyTag Type            Value 
                                            
   AESA       4001        20 OCTETS       ATM End System Address 
                                            
   VPVC       4002        4 OCTETS, 1st   VPCI/VCI.   
                           Least           Ref. : ITU Rec. Q.2931 
                           Significant 2 
                           OCTETS VPCI, 
                           2nd 2 OCTETS 
                           VCI 
                            
   SC         4003        Enumeration     Service Category: CBR(0), 
                                           nrt-VBR1(1), nrt-VBR2(2), 
                                           nrt-VBR3(3), rt-VBR1(4), rt-
                                           VBR2(5), rt-VBR3(6), 
                                           UBR1(7), UBR2(8), ABR(9). 
                                           Ref: ATM Forum UNI 4.0 
                                            
   BCOB       4004        5 bit integer   Broadband Bearer Class: 
     
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                                           Ref: ITU Rec. Q.2961.2 
                                            
   BBTC       4005        7 bit integer   Broadband Transfer 
                                           Capability: 
                                           Reference: ITU Rec. Q.2961 
                                            
   ATC        4006        Enumeration     I.371 ATM Traffic Capability 
                                           Reference: ITU Rec. I.371: 
                                           DBR(0), SBR1(1), SBR2(2), 
                                           SBR3(3), ABT/IT(4), 
                                           ABT/DT(5), ABR(6) 
                                            
   STC        4007        2 bits          Susceptibility to clipping: 
                                           Reference: ITU Rec. Q.2931 
                                           00      Susceptible 
                                           01      Not-susceptible 
                                            
   UPCC       4008        2 bits          User Plane Connection 
                                           configuration: 
                                           Reference: ITU 
                                           Recommendation Q.2931 
                                           00      Pt-to-pt,  
                                           01      Pt-to-mpt 
                                            
   PCR0       4009        24 bit integer  Peak Cell Rate (For CLP=0) 
                                           Reference: ITU Rec. Q.2931 
                                            
   SCR0       400A        24 bit integer  Sustainable Cell Rate (For 
                                           CLP=0) 
                                           Reference: ITU Rec. Q.2961 
                                            
   MBS0       400B        24 bit integer  Maximum Burst Size (For 
                                           CLP=0) 
                                           Reference: ITU Rec. Q.2961 
                                            
   PCR1       400C        24 bit integer  Peak Cell Rate (For CLP=0+1) 
                                           Reference: ITU Rec. Q.2931 
                                            
   SCR1       400D        24 bit integer  Sustainable Cell Rate (For 
                                           CLP=0+1) 
                                           Reference: ITU Rec. Q.2961 
                                            
   MBS1       400E        24 bit integer  Maximum Burst Size (For 
                                           CLP=0+1) 
                                           Reference: ITU Rec. Q.2961 
                                            
   BEI        400F        Boolean         Best Effort Indicator.  
                                           Ref.:  ATM Forum UNI 4.0 
                                           Value 1 indicates that BEI 
                                           is to be included in the ATM 
                                           signaling; value 0 indicates 
                                           that BEI is not to be 
                                           included in the ATM 
     
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                                           signaling. 
                                            
   TI         4010        Boolean         Tagging Indicator.   
                                           Ref.: ITU REc. Q.2961 
                                           Value 0 indicates that 
                                           tagging is not allowed; 
                                           value 1 indicates that 
                                           tagging is requested. 
                                            
   FD         4011        Boolean         Frame Discard.   
                                           Ref.:  ATM Forum UNI 4.0 
                                           Value 0 indicates that no 
                                           frame discard is allowed; 
                                           value 1 indicates that frame 
                                           discard is allowed. 
                                            
   A2PCDV     4012        24 bit integer  Acceptable 2-point CDV.  
                                           Ref.:  ITU Rec. Q.2965.2 
                                            
   C2PCDV     4013        24 bit integer  Cumulative 2-point CDV.  
                                           Ref.:  ITU Rec. Q.2965.2 
                                            
   APPCDV     4014        24 bit integer  Acceptable P-P CDV.   
                                           Ref.: ATM Forum UNI 4.0 
                                            
   CPPCDV     4015        24 bit integer  Cumulative P-P CDV.   
                                           Ref.: ATM Forum UNI 4.0 
                                            
   ACLR       4016        8 bit integer   Acceptable Cell Loss Ratio.  
                                           Ref.: ITU Rec. Q.2965.2, ATM 
                                           Forum UNI 4.0 
                                            
   MEETD      4017        16 bit integer  Maximum End-to-end transit 
                                           delay.   
                                           Ref.: ITU Rec. Q.2965.2, ATM 
                                           Forum UNI 4.0 
                                            
   CEETD      4018        16 bit integer  Cumulative End-to-end 
                                           transit delay.   
                                           Ref.: ITU Rec. Q.2965.2, ATM 
                                           Forum UNI 4.0 
                                            
   QosClass   4019        Integer 0-5     Qos Class 
                                           Reference: ITU 
                                           Recommendation Q.2965.1 
                                            
                                            Qos    Meaning 
                                            0      Default QoS 
                                            1      Stringent 
                                            2      Tolerant 
     
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                                            2      Tolerant 
                                            3      Bi-level 
                                            4      Unbounded 
                                            5      Stringent Bi-level 
                                                                                                
   AALtype    401A        1 OCTET         AAL Type 
                                           Reference: ITU Rec. Q.2931 
                                           00000000    AAL for voice 
                                           00000001    AAL type 1 
                                           00000010    AAL type 2 
                                           00000011    AAL type 3/4 
                                           00000101    AAL type 5 
                                           00010000    user defined AAL 
                         
                         
C.5     Frame Relay 
    
   PropertyID       PropertyTag    Type        Value 
                                                  
   DLCI             5001           Unsigned    Data link connection 
                                    Integer     id 
                                                  
   CID              5002           Unsigned    sub-channel id. 
                                    Integer 
                                     
   SID/Noiselevel   5003           Unsigned    silence insertion 
                                    Integer     descriptor  
                                                  
   Primary Payload  5004           Unsigned    Primary Payload 
   type                             Integer     TypeCovers FAX and 
                                                 codecs 
     
    
C.6     IP 
    
   PropertyID PropertyTag Type                Value 
                                                
   IPv4       6001        32 BITS Ipv4Address Ipv4Address: 
                                               Reference: IETF RFC791 
                                                
   IPv6       6002        128 BITS            IPv6 Address: 
                                               Reference: IETF RFC2460 
                                                
   Port       6003        unsigned integer    0-65535 
                                                
   Porttype   6004        enumerated          TCP(0), UDP(1), SCTP(2) 
    
    
C.7     ATM AAL2 
    
   PropertyID PropertyTag Type                  Value 
                                                   
   AESA       7001        20 OCTETS             AAL2 service endpoint 
     
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                                                  address as defined in 
                                                  ITU Rec. Q.2630.1 
                                                  ESEA 
                                                  NSEA 
                                                   
   BIR        See C.3     4 OCTETS              Served user generated 
                                                  reference as defined 
                                                  in ITU Rec. Q.2630.1 
                                                  SUGR 
                                                   
   ALC        7002        12 OCTETS             AAL2 link 
                                                  characteristics as 
                                                  defined in ITU Rec. 
                                                  Q.2630.1 
                                                  max/average CPS-SDU 
                                                  bitrate,  
                                                  max/average CPS-SDU 
                                                  size 
                                                   
   SSCS       7003        I.366.2: audio (8     Service specific 
                           OCTETS) multirate (3  convergence sublayer 
                           OCTETS) or I.366.1:   information as 
                           SAR-assured (14       defined in ITU Rec. 
                           OCTETS)/unassured (7  Q.2630.1 and used in 
                           OCTETS)               I.366.1 and I.366.2 
                                                  I.366.2: 
                                                  audio/multirate 
                                                  I.366.1:  
                                                  SAR-assured/unassured 
                                                   
   SUT        7004        1..254 octets         Served user transport 
                                                  parameter as defined 
                                                  in ITU Rec. Q.2630.1 
                                                   
   TCI        7005        BOOLEAN               Test connection 
                                                  indicator as defined 
                                                  in ITU Rec. Q.2630.1 
                                                   
   Timer_CU   7006        32 bit integer        Timer-CU 
                                                  Milliseconds to hold 
                                                  partially filled cell 
                                                  before sending. 
                                                   
   MaxCPSSDU  7007        8 bit integer         Maximum Common Part 
                                                  Sublayer Service Data 
                                                  Unit  
                                                  Ref ITU Rec. Q.2630.1  
                                                   
   CID        7008        8 bits                subchannel id, 0-255 
                                                  Ref.: Rec. I.363.2 
    
    
     
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C.8     ATM AAL1 
    
   PropertyID PropertyTag  Type       Value 
                                        
   BIR        See Table    4-29       GIT (Generic Identifier 
              C.3          OCTETS     Transport) 
                                       Ref.: Recommendation Q.2941.1 
                                        
   AAL1ST     8001         1 OCTET    AAL1 Subtype: 
                                       Reference: ITU Rec. Q.2931 
                                        00000000 Null 
                                        00000001 voiceband signal 
                                                 transport on 64kbit/s 
                                        00000010 circuit transport 
                                        00000100 high-quality audio 
                                                 signal transport 
                                        00000101 video signal 
                                                 transport 
                                                                                          
   CBRR       8002         1 OCTET    CBR Rate 
                                       Reference: ITU Rec. Q.2931 
                                       00000001           64 kbit/s 
                                       00000100       1544 kbit/s 
                                       00000101       6312 kbit/s 
                                       00000110      32064 kbit/s 
                                       00000111      44736 kbit/s 
                                       00001000      97728 kbit/s 
                                       00010000        2048 kbit/s 
                                       00010001        8448 kbit/s 
                                       00010010      34368 kbit/s 
                                       00010011    139264 kbit/s 
                                       01000000      n x 64 kbit/s 
                                       01000001        n * 8 kbit/s 
                                        
   MULT       See Table               Multiplier, or n x 64k/8k/300 
              C.9                     Reference: ITU Rec. Q.2931 
                                        
    SCRI      8003         1 OCTET    Source Clock Frequency Recovery 
                                       Method: 
                                       Reference: ITU Rec. Q.2931 
                                       00000000    NULL 
                                       00000001    SRTS 
                                       00000010    ACM 
                                        
   ECM        8004         1 OCTET    Error Correction Method: 
                                       Reference: ITU Rec. Q.2931 
                                       00000000    Null 
                                       00000001    FEC-LOSS 
                                       00000010    FEC-DELAY 
                                        
   SDTB       8005         16 bit     Structured Data Transfer 
                           integer    Blocksize: 
                                       Reference: ITU Rec. I.363.1 
     
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                                       Block size of SDT CBR service 
                                        
   PFCI       8006         8 bit      Partially filled cells 
                           integer    indentifier: 
                                       Reference: ITU Rec. I.363.1 
                                       1-47 
    
    
C.9     Bearer Capabilities 
    
   The table entries referencing ITU-T Recommendation Q.931 refer to 
   the encoding in the bearer capability information element of Q.931, 
   not to the low layer information element. 
    
   PropertyID    PropertyTag Type     Value 
                                        
   TMR           9001        1 OCTET  Transmission Medium Requirement 
                                       (Q.763)Reference: ITU Rec. Q.763 
                                       Bit 8 7 6 5 4 3 2 1 
                                       00000000 - speech 
                                       00000001 - spare 
                                       00000010 - 64 kbit/s 
                                       unrestricted 
                                       00000011 - 3.1 kHz audio 
                                       00000100 - reserved for 
                                       alternate speech (service 2)/64 
                                       kbit/s unrestricted (service 1)  
                                       00000101 “ reserved for 
                                       alternate 64 kbit/s unrestricted 
                                       (service 1)/speech (service 2)  
                                       00000110 - 64 kbit/s preferred 
                                       00000111 - 2 õ 64 kbit/s 
                                       unrestricted 
                                       00001000 - 384 kbit/s 
                                       unrestricted 
                                       00001001 - 1536 kbit/s 
                                       unrestricted 
                                       00001010 - 1920 kbit/s 
                                       unrestricted 
                                       00001011 through 00001111- spare 
                                       00010000 - 3 õ 64 kbit/s 
                                       unrestr. 
                                       00010001 - 4 õ 64 kbit/s 
                                       unrestr. 
                                       00010010 -  5 õ 64 kbit/s 
                                       unrestr. 
                                       00010011 spare 
                                       00010100 - 7 õ 64 kbit/s 
                                       unrestr. 
                                       00010101 - 8 õ 64 kbit/s 
                                       unrestr. 
                                       00010110 - 9 õ 64 kbit/s 
                                       unrestr. 
     
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                                       00010111 - 10 õ 64 kbit/s 
                                       unrestr. 
                                       00011000 - 11 õ 64 kbit/s 
                                       unrestr. 
                                       00011001 - 12 õ 64 kbit/s 
                                       unrestr. 
                                       00011010 - 13 õ 64 kbit/s 
                                       unrestr. 
                                       00011011 - 14 õ 64 kbit/s 
                                       unrestr. 
                                       00011100 “ 15 õ 64 kbit/s 
                                       unrestr. 
                                       00011101 “ 16 õ 64 kbit/s 
                                       unrestr. 
                                       00011110 “ 17 õ 64 kbit/s 
                                       unrestr. 
                                       00011111 “ 18 õ 64 kbit/s 
                                       unrestr. 
                                       00100000 “ 19 õ 64 kbit/s 
                                       unrestr. 
                                       00100001 “ 20 õ 64 kbit/s 
                                       unrestr. 
                                       00100010 “ 21 õ 64 kbit/s 
                                       unrestr. 
                                       00100011 “ 22 õ 64 kbit/s 
                                       unrestr. 
                                       00100100 - 23õ 64 kbit/s 
                                       unrestr. 
                                       00100101 “ spare 
                                       00100110 “ 25 õ 64 kbit/s 
                                       unrestr. 
                                       00100111 “ 26 õ 64 kbit/s 
                                       unrestr. 
                                       00101000 “ 27 õ 64 kbit/s 
                                       unrestr. 
                                       00101001 “ 28 õ 64 kbit/s 
                                       unrestr. 
                                       00101010 “ 29 õ 64 kbit/s 
                                       unrestr. 
                                       00101011 through 11111111 Spare 
                                        
   TMRSR         9002        1 OCTET  Transmission Medium Requirement 
                                       Subrate 
                                       0 “ unspecified 
                                       1 “ 8kbit/s 
                                       2 “ 16kbit/s 
                                       3 “ 32kbit/s 
                                        
   Contcheck     9003        BOOLEAN  Continuity Check 
                                       Reference: ITU Recommendation 
                                       Q.763 
                                       0 “ Not required on this circuit 
                                       1 “ Required on this circuit 
     
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   ITC           9004        5 BITS   Information Transfer 
                                       CapabilityReference: ITU Rec. 
                                       Q.763 
                                       Bits 5 4 3 2 1 
                                       00000 “ Speech 
                                       01000 -Unrestricted digital 
                                       information 
                                       01001- Restricted digital 
                                       information 
                                       10000 3.1 kHz audio 
                                       10001 - Unrestricted digital 
                                       information with 
                                       tones/announcements 
                                       11000 -Video 
                                       All other values are reserved. 
                                        
   TransMode     9005        2 BITS   Transfer Mode 
                                       Reference: ITU Rec. Q.931 
                                       Bit 2 1 
                                       00 “ Circuit mode 
                                       10 “ Packet mode 
                                        
   TransRate     9006        5 BITS   Transfer Rate 
                                       Reference: ITU Rec. Q.931 
                                       Bit 5 4 3 2 1 
                                       00000 “ This code shall be used 
                                       for packet mode calls 
                                       10000 - 64 kbit/s 
                                       10001 - 2 x 64 kbit/s 
                                       10011 -384 kbit/s 
                                       10101 -1536 kbit/s 
                                       10111 -1920 kbit/s 
                                       11000 - Multirate (64 kbit/s 
                                       base rate) 
                                        
   MULT          9007        7 BITS   Rate Multiplier: 
                                       Reference: ITU Rec. Q.931 
                                       Any value from 2 to n (maximum 
                                       number of B-channels) 
                                        
   layer1prot    9008        5 BITS   User Information Layer 1 
                                       Protocol 
                                       Reference: ITU Rec. Q.931 
                                       Bits 5 4 3 2 1 
                                       00001 “ CCITT standardized rate 
                                       adaption V.110 and X.30.  
                                       00010 - Rec. G.711  u-law 
                                       00011 - Rec. G.711 A-law 
                                       00100 “ Rec. G.721 32 kbit/s 
                                       ADPCM and Rec. I.460. 
                                       00101 - Recs. H.221 and H.242 
                                       00110 “ Recs. H.223 and H.245 
     
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                                       00111 “ Non-ITU-T standardized 
                                       rate adaption.   
                                       01000 “ ITU-T standardized rate 
                                       adaption V.120.  
                                       01001 “ CCITT standardized rate 
                                       adaption X.31 HDLC flag 
                                       stuffing.  All other values are 
                                       reserved. 
                                        
   syncasync     9009        BOOLEAN  Synchronous/Asynchronous 
                                       Reference: ITU Rec. Q.931 
                                       0 “ Synchronous data 
                                       1 - Asynchronous data 
                                        
   negotiation   900A        BOOLEAN  Negotiation 
                                       Reference: ITU Rec. Q.931 
                                       0 - In-band negotiation possible 
                                       1 - In-band negotiation not 
                                       possible 
                                        
   Userrate      900B        5 BITS   User Rate 
                                       Reference: ITU Rec. Q.931 
                                       Bits 5 4 3 2 1 
                                       00000 - Rate is indicated by E-
                                       bits specified in Rec. I.460  or 
                                       may be negotiated in-band 
                                       00001 - 0.6 kbit/s 
                                       Recommendations V.6  and X.1 
                                       00010 - 1.2 kbit/s Rec. V.6 
                                       00011 - 2.4 kbit/s Recs. V.6 and 
                                       X.1 
                                       00100 - 3.6 kbit/s Rec. V.600101 
                                       - 4.8 kbit/s Recs. V.6 and X.1 
                                       00110 - 7.2 kbit/s Rec. V.6 
                                       00111 - 8 kbit/s Rec. I.460 
                                       01000 - 9.6 kbit/s Recs. V.6 and 
                                       X.1 
                                       01001 - 14.4 kbit/s Rec. V.6 
                                       01010 “ 16 kbit/s Rec. I.460 
                                       01011 “ 19.2 kbit/s Rec. V.6 
                                       01100 - 32 kbit/s Rec. I.460 
                                       01101 “ 38.4 kbit/s Rec. V.110 
                                       01110 - 48 kbit/s 
                                       Recommendations V.6 and X.1 
                                       01111 “ 56 kbit/s Rec. V.6 
                                       10010 “ 57.6 kbit/s Rec. V.14 
                                       extended 
                                       10011 “ 28.8 kbit/s Rec. V.110 
                                       10100 “ 24 kbit/s Rec. V.110 
                                       10101 - 0.1345 kbit/s Rec. X.1 
                                       10110 - 0.100 kbit/s Rec. X.1 
                                       10111 - 0.075/1.2 kbit/s 
                                       Recommendations V.6 and X.1 
     
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                                       11000 - 1.2/0.075 kbit/s 
                                       Recommendations V.6 and X.1 
                                       11001 - 0.050 kbit/s 
                                       Recommendations V.6 and X.1 
                                       11010 - 0.075 kbit/s 
                                       Recommendations V.6 and X.1 
                                       11011 - 0.110 kbit/s 
                                       Recommendations V.6 and X.1 
                                       11100 - 0.150 kbit/s 
                                       Recommendations V.6 and X.1 
                                       11101 - 0.200 kbit/s 
                                       Recommendations V.6 and X.1 
                                       11110 - 0.300 kbit/s 
                                       Recommendations V.6 and X.1 
                                       11111 “ 12 kbit/s Rec. V.6 
                                       All other values are reserved. 
                                        
   INTRATE       900C        2 BITS   Intermediate Rate 
                                       Reference: ITU Rec. Q.931 
                                       Bit 2 1 
                                       00 - Not used 
                                       01 “ 8 kbit/s 
                                       10 - 16 kbit/s 
                                       11 - 32 kbit/s 
                                        
   nictx         900D        BOOLEAN  Network Independent Clock (NIC) 
                                       on transmission 
                                       Reference: ITU Rec. Q.931 
                                       0 - Not required to send data 
                                       with network independent clock 
                                       1 - Required to send data with 
                                       network independent clock 
                                        
   nicrx         900E        BOOLEAN  Network independent clock (NIC) 
                                       on reception 
                                       Reference: ITU Rec. Q.931 
                                       0 - Cannot accept data with 
                                       network independent clock (i.e. 
                                       sender does not support this 
                                       optional procedure) 
                                       1 - Can accept data with network 
                                       independent clock (i.e. sender 
                                       does support this optional 
                                       procedure) 
                                        
   flowconttx    900F        BOOLEAN  Flow Control on transmission 
                                       (Tx) 
                                       Reference: ITU Rec. Q.931 
                                       0 - Not required to send data 
                                       with flow control mechanism 
                                       1 - Required to send data with 
                                       flow control mechanism 
                                        
     
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   flowcontrx    9010        BOOLEAN  Flow control on reception (Rx) 
                                       Reference: ITU Rec. Q.931 
                                       0 - Cannot accept data with flow 
                                       control mechanism (i.e. sender 
                                       does not support this optional 
                                       procedure) 
                                       1 - Can accept data with flow 
                                       control mechanism (i.e. sender 
                                       does support this optional 
                                       procedure) 
                                        
   rateadapthdr  9011        BOOLEAN  Rate adaption header/no header 
                                       Reference: ITU Rec. Q.931 
                                       0 - Rate adaption header not 
                                       included 
                                       1 - Rate adaption header 
                                       included 
                                        
   multiframe    9012        BOOLEAN  Multiple frame establishment 
                                       support in data link 
                                       Reference: ITU Rec. Q.931 
                                       0 - Multiple frame establishment 
                                       not supported. Only UI frames 
                                       allowed. 
                                       1 - Multiple frame establishment 
                                       supported 
                                        
   OPMODE        9013        BOOLEAN  Mode of operation 
                                       Reference: ITU Rec. Q.931 
                                       0 Bit transparent mode of 
                                       operation 
                                       1 Protocol sensitive mode of 
                                       operation 
                                        
   llidnegot     9014        BOOLEAN  Logical link identifier 
                                       negotiation 
                                       Reference: ITU Rec. Q.931 
                                       0 Default, LLI = 256 only 
                                       1 Full protocol negotiation 
                                        
   assign        9015        BOOLEAN  Assignor/assignee 
                                       Reference: ITU Rec. Q.931 
                                       0 Message originator is ŸDefault 
                                       assignee÷ 
                                       1 Message originator is 
                                       ŸAssignor only÷ 
                                        
   inbandneg     9016        BOOLEAN  In-band/out-band negotiation 
                                       Reference: ITU Rec. Q.931 
                                       0 - Negotiation is done with 
                                       USER INFORMATION messages on a 
                                       temporary signalling connection 
                                       1 - Negotiation is done in-band 
     
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                                       using logical link zero 
                                        
   stopbits      9017        2 BITS   Number of stop bits 
                                       Reference: ITU Rec. Q.931 
                                       Bits 2 1 
                                       00 - Not used 
                                       01 - 1 bit 
                                       10 - 1.5 bits 
                                       11 - 2 bits 
                                        
   databits      9018        2 BIT    Number of data bits excluding 
                                       parity Bit if present 
                                       Reference: ITU Rec. Q.931 
                                       Bit 2 1 
                                       00 - Not used 
                                       01 -5 bits 
                                       10 - 7 bits 
                                       11 - 8 bits 
                                        
   parity        9019        3 BIT    Parity information 
                                       Reference: ITU Rec. Q.931 (1998) 
                                       Bit 3 3 (sic) 1 
                                       000 “ Odd 
                                       010 - Even 
                                       011 -None 
                                       100 - Forced to 0 
                                       101 - Forced to 1 
                                       All other values are reserved. 
                                        
   duplexmode    901A        BOOLEAN  Mode duplex 
                                       Reference: ITU Rec. Q.931 
                                       0 - Half duplex 
                                       1 - Full duplex 
   modem         901B        6 BIT    Modem Type 
                                       Reference: ITU Rec. Q.931 
                                       Bits 6 5 4 3 2 1 
                                       000000 through 000101 National 
                                       Use 
                                       010001 “ Recommendation V.21 
                                       010010 “ Recommendation V.22 
                                       010011 - Recommendation V.22 bis 
                                       010100 - Recommendation V.23 
                                       010101 - Recommendation V.26 
                                       011001 - Recommendation V.26 bis 
                                       010111 - Recommendation V.26 ter 
                                       011000 - RecommendationV.27 
                                       011001 - Recommendation V.27 bis 
                                       011010 - Recommendation V.27 ter 
                                       011011 “ Recommendation V.29 
                                       011101 “ Recommendation V.32 
                                       011110 “ Recommendation V.34 
                                       100000 through 101111 National 
                                       Use 
     
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                                       110000 through 111111 User 
                                       Specified 
                                        
   layer2prot    901C        5 BIT    User information layer 2 
                                       protocol 
                                       Reference: ITU Rec. Q.931 
                                       Bit 5 4 3 2 1 
                                       00010 - Rec. Q.921/I.441 [3] 
                                       00110 - Rec. X.25 [5], link 
                                       layer 
                                       01100 “ LAN logical link control 
                                       (ISO/IEC 8802-2) 
                                       All other values are reserved. 
                                        
   layer3prot    901D        5 BIT    User information layer 3 
                                       protocol 
                                       Reference: ITU Rec. Q.931 
                                       Bit 5 4 3 2 1 
                                       00010 - Rec. Q.931/I.451 
                                       00110 - Rec. X.25, packet layer 
                                       01011 “ ISO/IEC TR 9577 
                                       (Protocol identification in the 
                                       network layer) 
                                       All other values are reserved. 
                                        
   addlayer3prot 901E        OCTET    Additional User Information 
                                       layer 3 protocol 
                                       Reference: ITU Rec. Q.931Bits 
                                       4321 4321 
                                       1100 1100 - Internet Protocol 
                                       (RFC 791) (ISO/IEC TR 9577) 
                                       1100 1111 - Point-to-point 
                                       Protocol (RFC 1661) 
   DialledN      901F        30       Dialled Number 
                              OCTETS 
                               
   DiallingN     9020        30       Dialling Number 
                              OCTETS 
   ECHOCI        9021                 Not Used. See H.248 E.13 for an 
                                       example of possible Echo Control 
                                       properties. 
                                        
   NCI           9022        1 OCTET  Nature of Connection Indicators 
                                       Reference: ITU Rec. Q.763 
                                       Bits 8 7 6 5 4 3 2 1 
                                       Bits 2 1 Satellite Indicator 
                                       0 0  no satellite circuit in the 
                                       connection 
                                       0 1  one satellite circuit in 
                                       the connection 
                                       1 0  two satellite circuits in 
                                       the connection 
                                       1 1  spare 
     
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                                       Bits 4 3 Continuity check 
                                       indicator 
                                       0 0  continuity check not 
                                       required 
                                       0 1  continuity check required 
                                       on this circuit 
                                       1 0  continuity check performed 
                                       on a previous circuit 
                                       1 1  spare 
                                       Bits 5 Echo control device 
                                       indicator  
                                       0  outgoing echo control device 
                                       not included 
                                       1   outgoing echo control device 
                                       included 
                                       Bits 8 7 6 Spare 
                                        
   USI           9023        OCTET    User Service Information 
                              STRING   Reference ITU Recommendation 
                                       Q.763 Section 3.57 
    
    
C.10    AAL5 Properties 
    
   PropertyID PropertyTag  Type      Value 
                                       
   FMSDU      A001         32 bit    Forward Maximum CPCS-SDU Size: 
                           integer   Reference: ITU Rec. Q.2931 
                                      Maximum CPCS-SDU size sent in the 
                                      direction from the calling user 
                                      to the called user. 
                                       
   BMSDU      A002         32 bit    Backwards Maximum CPCS-SDU Size 
                           integer   Reference: ITU Rec. Q.2931 
                                      Maximum CPCS-SDU size sent in the 
                                      direction from the called user to 
                                      the calling user. 
                                       
   SSCS       See table    See table See table C.7 
              C.7          C.7       Additional values: VPI/VCI 
    
    
C.11    SDP Equivalents 
    
   PropertyID PropertyTag Type   Value 
                                   
   SDP_V      B001        STRING Protocol Version 
                                  Reference: IETF RFC2327 
                                   
   SDP_O      B002        STRING Owner/creator and session ID 
                                  Ref.: RFC2327 
                                   
   SDP_S      B003        STRING Sesson name 
     
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                                  Ref.: RFC2327 
                                   
   SDP_I      B004        STRING Session identifier 
                                  Ref.: RFC2327 
                                   
   SDP_U      B005        STRING URI of descriptor 
                                  Ref.: RFC2327 
                                   
   SDC_E      B006        STRING email address 
                                  Ref.: RFC2327 
                                   
   SDP_P      B007        STRING phone number 
                                  Ref.: RFC2327 
                                   
   SDP_C      B008        STRING Connection information 
                                  Reference: IETF RFC2327 
                                   
   SDP_B      B009        STRING Bandwidth Information 
                                  Reference: IETF RFC2327 
                                   
   SDP_Z      B00A        STRING time zone adjustment 
                                  Ref.: RFC2327 
                                   
   SDP_K      B00B        STRING Encryption Key 
                                  Reference: IETF RFC2327 
                                   
   SDP_A      B00C        STRING Zero or more session attributes 
                                  Reference: IETF RFC2327 
                                   
   SDP_T      B00D        STRING Active Session Time 
                                  Reference: IETF RFC2327 
                                   
   SDP_R      B00E        STRING Zero or more repeat times 
                                  Reference: IETF RFC2327 
                                   
   SDP_M      B00F        STRING Media name and transport 
                                  addressReference: IETF RFC2327 
    
    
C.12    H.245 
    
   PropertyID PropertyTag Type     Value 
                                     
   OLC        C001        octet    The value of H.245 
                           string   OpenLogicalChannel structure. 
                                    Reference: ITU Recommendation H.245 
                                     
   OLCack     C002        octet    The value of H.245 
                           string   OpenLogicalChannelAck structure. 
                                    Reference: ITU Recommendation H.245 
                                     
   OLCcnf     C003        octet    The value of H.245 
                           string   OpenLogicalChannelConfirm 
     
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                                    structure. 
                                    Reference: ITU Recommendation H.245 
                                     
   OLCrej     C004        octet    The value of H.245 
                           string   OpenLogicalChannelReject structure. 
                                    Reference: ITU Recommendation H.245 
                                     
   CLC        C005        octet    The value of H.245 
                           string   CloseLogicalChannel structure. 
                                    Reference: ITU Recommendation H.245 
                                     
   CLCack     C006        octet    The value of H.245 
                           string   CloseLogicalChannelAck structure. 
                                    Reference: ITU Recommendation H.245 
    
    
     
     
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ANNEX D TRANSPORT OVER IP (NORMATIVE) 
    
D.1     Transport over IP/UDP using Application Level Framing 
    
   Protocol messages defined in this document may be transmitted over 
   UDP.  When no port is provided by the peer (see section 7.2.8), 
   commands should be sent to the default port number, 2944 for text-
   encoded operation or 2945 for binary-encoded operation.  Responses 
   must be sent to the address and port from which the corresponding 
   commands were sent. 
    
   ALF is a set of techniques that allow an application, as opposed to 
   a stack, to affect how messages are sent to the other side. A 
   typical ALF technique is to allow an application to change the order 
   of messages sent when there is a queue AFTER it has queued them.  
   There is no formal specification for ALF. The procedures in Annex 
   D.1 contain a minimum suggested set of ALF behaviors 
   Implementors using IP/UDP with ALF should be aware of the 
   restrictions of the MTU on the maximum message size. 
    
D.1.1   Providing At-Most-Once Functionality 
    
   Messages, being carried over UDP, may be subject to losses. In the 
   absence of a timely response, commands are repeated. Most commands 
   are not idempotent.  The state of the MG would become unpredictable 
   if, for example, Add commands were executed several times.  The 
   transmission procedures shall thus provide an "At- Most-Once" 
   functionality. 
    
   Peer protocol entities are expected to keep in memory a list of the 
   responses that they sent to recent transactions and a list of the 
   transactions that are currently outstanding. The transaction 
   identifier of each incoming message is compared to the transaction 
   identifiers of the recent responses sent to the same MId. If a match 
   is found, the entity does not execute the transaction, but simply 
   repeats the response. If no match is found, the message will be 
   compared to the list of currently outstanding transactions. If a 
   match is found in that list, indicating a duplicate transaction, the 
   entity does not execute the transaction (see section D.1.4 for 
   procedures on sending TransactionPending). 
    
   The procedure uses a long timer value, noted LONG-TIMER in the 
   following.  The timer should be set larger than the maximum duration 
   of a transaction, which should take into account the maximum number 
   of repetitions, the maximum value of the repetition timer and the 
   maximum propagation delay of a packet in the network.  A suggested 
   value is 30 seconds. 
    
   The copy of the responses may be destroyed either LONG-TIMER seconds 
   after the response is issued, or when the entity receives a 
   confirmation that the response has been received, through the 
   "Response Acknowledgement parameter". For transactions that are 
   acknowledged through this parameter, the entity shall keep a copy of 
   the transaction-id for LONG-TIMER seconds after the response is 
     
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   issued, in order to detect and ignore duplicate copies of the 
   transaction request that could be produced by the network. 
    
D.1.2   Transaction identifiers and three-way handshake 
    
D.1.2.1 Transaction identifiers 
    
   Transaction identifiers are 32 bit integer numbers.  A Media Gateway 
   Controller may decide to use a specific number space for each of the 
   MGs that they manage, or to use the same number space for all MGs 
   that belong to some arbitrary group.  MGCs may decide to share the 
   load of managing a large MG between several independent processes.  
   These processes will share the same transaction number space.  There 
   are multiple possible implementations of this sharing, such as 
   having a centralized allocation of transaction identifiers, or pre-
   allocating non-overlapping ranges of identifiers to different 
   processes.  The implementations shall guarantee that unique 
   transaction identifiers are allocated to all transactions that 
   originate from a logical MGC (identical mId). MGs can simply detect 
   duplicate transactions by looking at the transaction identifier and 
   mId only. 
    
D.1.2.2 Three-way handshake 
    
   The TransactionResponse Acknowledgement parameter can be found in 
   any message. It carries a set of "confirmed transaction-id ranges". 
   Entities may choose to delete the copies of the responses to 
   transactions whose id is included in "confirmed transaction-id 
   ranges" received in the transaction response messages. They should 
   silently discard further commands when the transaction-id falls 
   within these ranges. 
    
   The "confirmed transaction-id ranges" values shall not be used if 
   more than LONG-TIMER seconds have elapsed since the MG issued its 
   last response to that MGC, or when a MG resumes operation.  In this 
   situation, transactions should be accepted and processed, without 
   any test on the transaction.id. 
    
   Messages that carry the "Transaction Response Acknowledgement" 
   parameter may be transmitted in any order.  The entity shall retain 
   the "confirmed transaction-id ranges" receivedfor LONG-TIMER 
   seconds. 
    
   In the binary encoding, if only the firstAck is present in a 
   response acknowledgement (see Annex A.2), only one transaction is 
   acknowledged.  If both firstAck and lastAck are present, then the 
   range of transactions from firstAck to lastAck is acknowledged.  In 
   the text encoding, a horizontal dash is used to indicate a range of 
   transactions being acknowledged (see Annex B.2). 
    
D.1.3   Computing retransmission timers 
    
   It is the responsibility of the requesting entity to provide 
   suitable time outs for all outstanding transactions, and to retry 
     
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   transactions when time outs have been exceeded. Furthermore, when 
   repeated transactions fail to be acknowledged, it is the 
   responsibility of the requesting entity to seek redundant services 
   and/or clear existing or pending connections. 
    
   The specification purposely avoids specifying any value for the 
   retransmission timers. These values are typically network dependent. 
   The retransmission timers should normally estimate the timer value 
   by measuring the time spent between the sending of a command and the 
   return of a response. Implementations SHALL ensure that the 
   algorithm used to calculate retransmission timing performs an 
   exponentially increasing backoff of the retransmission timeout for 
   each retransmission or repetition after the first one. 
    
   Note - One possibility is to use the algorithm implemented in TCP-
   IP, which uses two variables: 
    
   ¦    The average acknowledgement delay, AAD, estimated through an 
   exponentially smoothed average of the observed delays. 
    
   ¦    The average deviation, ADEV, estimated through an exponentially 
   smoothed average of the absolute value of the difference between the 
   observed delay and the current average.  The retransmission timer, 
   in TCP, is set to the sum of the average delay plus N times the 
   average deviation. The maximum value of the timer should however be 
   bounded for the protocol defined in this document, in order to 
   guarantee that no repeated packet would be received by the gateways 
   after LONG-TIMER seconds.  A suggested maximum value is 4 seconds. 
    
   After any retransmission, the entity SHOULD do the following:  
    
   ¦    It should double the estimated value of the average delay, AAD 
    
   ¦    It should compute a random value, uniformly distributed between 
   0.5 AAD and AAD 
    
   ¦    It should set the retransmission timer to the sum of that 
   random value and N times the average deviation. 
    
   This procedure has two effects. Because it includes an exponentially 
   increasing component, it will automatically slow down the stream of 
   messages in case of congestion. Because it includes a random 
   component, it will break the potential synchronization between 
   notifications triggered by the same external event. 
    
D.1.4   Provisional responses 
    
   Executing some transactions may require a long time. Long execution 
   times may interact with the timer based retransmission procedure. 
   This may result either in an inordinate number of retransmissions, 
   or in timer values that become too long to be efficient. Entities 
   that can predict that a transaction will require a long execution 
   time may send a provisional response, "Transaction Pending".  They 
     
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   SHOULD send this response if they receive a repetition of a 
   transaction that is still being executed. 
    
   Entities that receive a Transaction Pending shall switch to a 
   different repetition timer for repeating requests.  The root 
   termination has a property (ProvisionalResponseTimerValue), which 
   can be set to the requested maximum number of milliseconds between 
   receipt of a command and transmission of the TransactionPending 
   response.  Upon receipt of a final response following receipt of 
   provisional responses, an immediate confirmation shall be sent, and 
   normal repetition timers shall be used thereafter.  An entity that 
   sends a provisional response, SHALL include the immAckRequired field 
   in the ensuing final response, indicating that an immediate 
   confirmation is expected.  Receipt of a Transaction Pending after 
   receipt of a reply shall be ignored. 
    
D.1.5   Repeating Requests, Responses and Acknowledgements 
    
   The protocol is organized as a set of transactions, each of which is 
   composed request and a response, commonly referred to as an 
   acknowledgement.  The protocol messages, being carried over UDP, may 
   be subject to losses. In the absence of a timely response, 
   transactions are repeated. Entities are expected to keep in memory a 
   list of the responses that they sent to recent transactions, i.e. a 
   list of all the responses they sent over the last LONG-TIMER 
   seconds, and a list of the transactions that are currently being 
   executed. 
    
   The repetition mechanism is used to guard against three types of 
   possible errors: 
    
   ¦    transmission errors, when for example a packet is lost due to 
   noise on a line or congestion in a queue; 
    
   ¦    component failure, when for example an interface to a entity 
   becomes unavailable; 
    
   ¦    entity failure, when for example an entire entity become 
   unavailable. 
    
   The entities should be able to derive from the past history an 
   estimate of the packet loss rate due to transmission errors.  In a 
   properly configured system, this loss rate should be kept very low, 
   typically less than 1%.  If a Media Gateway Controller or a Media 
   Gateway has to repeat a message more than a few times, it is very 
   legitimate to assume that something else than a transmission error 
   is occurring.  For example, given a loss rate of 1%, the probability 
   that five consecutive transmission attempts fail is 1 in 100 
   billion, an event that should occur less than once every 10 days for 
   a Media Gateway Controller that processes 1 000 transactions per 
   second. (Indeed, the number of repetition that is considered 
   excessive should be a function of the prevailing packet loss rate.) 
   We should note that the "suspicion threshold", which we will call 
     
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   "Max1", is normally lower than the "disconnection threshold", which 
   should be set to a larger value. 
    
   A classic retransmission algorithm would simply count the number of 
   successive repetitions, and conclude that the association is broken 
   after retransmitting the packet an excessive number of times 
   (typically between 7 and 11 times.) In order to account for the 
   possibility of an undetected or in.progress "failover", we modify 
   the classic algorithm so that if the Media Gateway receives a valid 
   ServiceChange message announcing a failover, it will start 
   transmitting outstanding commands to that new MGC.  Responses to 
   commands are still transmitted to the source address of the command. 
    
   In order to automatically adapt to network load, this document 
   specifies exponentially increasing timers.  If the initial timer is 
   set to 200 milliseconds, the loss of a fifth retransmission will be 
   detected after about 6 seconds.  This is probably an acceptable 
   waiting delay to detect a failover.   The repetitions should 
   continue after that delay not only in order to perhaps overcome a 
   transient connectivity problem, but also in order to allow some more 
   time for the execution of a failover - waiting a total delay of 30 
   seconds is probably acceptable. 
    
   It is, however, important that the maximum delay of retransmissions 
   be bounded.  Prior to any retransmission, it is checked that the 
   time elapsed since the sending of the initial datagram is no greater 
   than T-MAX. If more than T-MAX time has elapsed, the MG concludes 
   that the MGC has failed, and it begins its recovery process as 
   described in section 11.5. If. the MG retries the current MGC it 
   shall use a ServiceChange with ServiceChangeMethod set to 
   Disconnected so that the new MGC will be aware that the MG lost one 
   or more transactions.  The value T-MAX is related to the LONG-TIMER 
   value: the LONG-TIMER value is obtained by adding to T-MAX the 
   maximum propagation delay in the network. 
    
D.2      Using TCP 
    
   Protocol messages as defined in this document may be transmitted 
   over TCP.  When no port is specified by the other side (see section 
   7.2.8), the commands should be sent to the default port. The defined 
   protocol has messages as the unit of transfer, while TCP is a 
   stream-oriented protocol.  TPKT, according to RFC1006 SHALL be used 
   to delineate messages within the TCP stream. 
    
   In a transaction-oriented protocol, there are still ways for 
   transaction requests or responses to be lost.  As such, it is 
   recommended that entities using TCP transport implement application 
   level timers for each request and each response, similar to those 
   specified for application level framing over UDP. 
    
D.2.1   Providing the At-Most-Once functionality 
    
   Messages, being carried over TCP, are not subject to transport 
   losses, but loss of a transaction request or its reply may 
     
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   nonetheless be noted in real implementations. In the absence of a 
   timely response, commands are repeated. Most commands are not 
   idempotent.  The state of the MG would become unpredictable if, for 
   example, Add commands were executed several times.   
    
   To guard against such losses, it is recommended that entities follow 
   the procedures in section D.1.1 
    
D.2.2   Transaction identifiers and three way handshake 
    
   For the same reasons, it is possible that transaction replies may be 
   lost even with a reliable delivery protocol such as TCP.  It is 
   recommended that entities follow the procedures in section D.1.2.2. 
    
D.2.3   Computing retransmission timers 
    
   With reliable delivery, the incidence of loss of a transaction 
   request or reply is expected to be very low.  Therefore, only simple 
   timer mechanisms are required. Exponential back-off algorithms 
   should not be necessary, although they could be employed where, as 
   in an MGC, the code to do so is already required, since MGCs must 
   implement ALF/UDP as well as TCP. 
    
D.2.4   Provisional responses 
    
   As with UDP, executing some transactions may require a long time. 
   Entities that can predict that a transaction will require a long 
   execution time may send a provisional response, "Transaction 
   Pending". They should send this response if they receive a 
   repetition of a transaction that is still being executed. 
    
   Entities that receive a Transaction Pending shall switch to a longer 
   repetition timer for that transaction. 
    
   Entities shall retain Transactions and replies until they are 
   confirmed.  The basic procedure of section D.1.4 should be followed, 
   but simple timer values should be sufficient. There is no need to 
   send an immediate confirmation upon receipt of a final response. 
    
D.2.5   Ordering of commands 
    
   TCP provides ordered delivery of transactions.  No special 
   procedures are required.  It should be noted that ALF/UDP allows 
   sending entity to modify its behavior under congestion, and in 
   particular, could reorder transactions when congestion is 
   encountered.  TCP could not achieve the same results. 
     
     
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ANNEX E BASIC PACKAGES (NORMATIVE) 
    
   This Annex contains definitions of some packages for use with 
   Recommendation H.248. 
    
E.1     Generic 
    
   PackageID: g (0x0001) 
   Version: 1 
   Extends: None 
    
   Description: 
   Generic package for commonly encountered items 
    
E.1.1   Properties 
    
   None 
    
E.1.2   Events 
    
   Cause 
   EventID: cause (0x0001) 
    
   Generic error event 
    
   ObservedEvents Descriptor Parameters: 
    
      General Cause 
    
         ParameterID: Generalcause (0x0001) 
          
         This parameter groups the failures into six groups, which the 
         MGC may act upon. 
          
         Possible values: Enumerated, 
            "NR" Normal Release (0x0001) 
            "UR" Unavailable Resources (0x0002) 
            "FT" Failure, Temporary (0x0003) 
            "FP" Failure, Permanent (0x0004) 
            "IW" Interworking Error (0x0005) 
            "UN" Unsupported (0x0006) 
       
      Failure Cause 
         ParameterID: Failurecause (0x0002) 
          
         Possible Values: OCTET STRING 
          
         Description: The Release Cause is the value generated by the  
         Released equipment, i.e. a released network connection.   
         The concerned value is defined in the appropriate bearer 
         control protocol. 
    
   Signal Completion 
   EventID: sc (0x0002) 
     
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   Indicates termination of one or more signals for which the 
   notifyCompletion parameter was set to "ON".  For further procedural 
   description, see sections 7.1.11, 7.1.17, and 7.2.7. 
    
   ObservedEvents Descriptor parameters: 
    
      Signal Identity 
    
         ParameterID:  SigID (0x0001) 
         
         This parameter identifies the signals which have terminated. 
         
         Type: list 
         
        Possible values: a list of signals and/or sequential signal 
        lists which have terminated.  A signal outside of a sequential 
        signal list shall be identified using the pkgdName syntax 
        without wildcarding.  An individual signal inside of a 
        sequential signal list shall be identified using the sequential 
        signal list syntax with the correct signal list identifier, 
        enclosing the name of the specific signal which terminated in 
        pkgdName syntax. 
    
      Termination Method 
       
        ParameterID:  Meth (0x0002) 
         
        Indicates the means by which the signal terminated. 
         
        Type: enumeration 
         
        Possible values: 
           "TO" (0x0001) Signal timed out or otherwise completed on its 
                          own 
           "EV" (0x0002) Interrupted by event 
           "SD" (0x0003) Halted by new Signals Descriptor 
           "NC" (0x0004) Not completed, other cause 
    
      Signal List ID 
       
        ParameterID:  SLID (0x0003) 
         
        Indicates to which signal list a signal belongs. The SignalList 
                ID is only returned in cases where the signal resides 
                in a signal list. 
         
        Type: integer 
         
        Possible values: Any integer 
    
E.1.3   Signals 
    
   None 
     
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E.1.4   Statistics 
    
   None 
    
    
E.2     Base Root Package 
    
   Base Root Package 
   PackageID: root (0x0002) 
   Version: 2 
   Extends: None 
    
   Description: 
   This package defines Gateway wide properties. 
    
E.2.1   Properties 
    
   MaxNrOfContexts 
      PropertyID: maxNumberOfContexts (0x0001) 
       
      The value of this property gives the maximum number of contexts 
      that can exist at any time.  The NULL context is not included in 
      this number. 
       
      Type: Double 
       
      Possible values: 1 and up 
       
      Defined in: TerminationState 
       
      Characteristics: read only 
    
   MaxTerminationsPerContext 
      PropertyID: maxTerminationsPerContext (0x0002) 
       
      The maximum number of allowed terminations in a context, see 
      section 6.1 
       
      Type: Integer 
       
      Possible Values: any integer 
       
      Defined In: TerminationState 
       
      Characteristics: read only 
    
   normalMGExecutionTime 
      PropertyId: normalMGExecutionTime (0x0003) 
       
      Settable by the MGC to indicate the interval within which the MGC 
      expects a response to any transaction from the MG (exclusive of 
      network delay) 
       
     
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      Type: Integer 
       
      Possible Values: any integer, represents milliseconds 
       
      Defined in: TerminationState 
       
      Characteristics: read / write 
    
   normalMGCExecutionTime 
      PropertyId: normalMGCExecutionTime (0x0004) 
       
      Settable by the MGC to indicate the interval within which the MG 
      should expects a response to any transaction from the MGC 
      (exclusive of network delay) 
       
      Type: Integer 
       
      Possible Values: any integer, represents milliseconds 
       
      Defined in: TerminationState 
       
      Characteristics: read / write 
    
   MGProvisionalResponseTimerValue 
      PropertyId: MGProvisionalResponseTimerValue (0x0005) 
       
      Indicates the time within which the MGC should expect a Pending 
      Response from the MG if a Transaction cannot be completed.  
      Initially set to normalMGExecutionTime, plus network delay, but 
      may be lowered. 
       
      Type: Integer 
       
      Possible Values: any integer, represents milliseconds 
       
      Defined in: TerminationState 
       
      Characteristics: read / write  
    
   MGCProvisionalResponseTimerValue 
      PropertyId: MGCProvisionalResponseTimerValue (0x0006) 
       
      Indicates the time within which the MG should expect a Pending 
      Response from the MGC if a Transaction cannot be completed.  
      Initially set to normalMGCExecutionTime, plus network delay, but 
      may be lowered. 
       
      Type: Integer 
       
      Possible Values: any integer, represents milliseconds 
       
      Defined in: TerminationState 
       
      Characteristics: read / write 
     
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   MGCOriginatedPendingLimit 
      PropertyId: MGCOriginatedPendingLimit (0x0005) 
       
      Indicates the number of TransactionPendings that can be received 
      from the MGC. Once this limit is exceeded the MGC should issue a 
      TransactionReply with error code 5xx Number of 
      TransactionPendings Exceeded, otherwise the MG can assume the 
      Transaction to be in error. 
       
      Type: Integer 
       
      Possible Values: any integer 
       
      Defined in: TerminationState 
       
      Characteristics: Read/Write 
         
   MGOriginatedPendingLimit  
      PropertyId: MGOriginatedPendingLimit (0x0006) 
       
      Indicates the number of TransactionPendings that can be received 
      from the MG. Once this limit is exceeded the MG should issue a 
      TransactionReply with error code 5xx Number of 
      TransactionPendings Exceeded, otherwise the MGC can assume the 
      Transaction to be in error.  
       
      Type: Integer 
       
      Possible Values: any integer 
       
      Defined in: TerminationState  
       
      Characteristics: Read/Write 
    
E.2.2   Events 
    
   None 
    
E.2.3   Signals 
    
   None 
    
E.2.4   Statistics 
    
   None 
    
E.2.5   Procedures 
    
   None 
    
     
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E.3     Tone Generator Package 
    
   PackageID: tonegen (0x0003) 
   Version: 1 
   Extends: None 
    
   Description: 
   This package defines signals to generate audio tones. This package 
   does not specify parameter values. It is intended to be extendable. 
   Generally, tones are defined as an individual signal with a 
   parameter, ind, representing "interdigit" time delay, and a tone id 
   to be used with playtones.  A tone id should be kept consistent with 
   any tone generation for the same tone. MGs are expected to be 
   provisioned with the characteristics of appropriate tones for the 
   country in which the MG is located.  
    
E.3.1   Properties 
    
   None 
    
E.3.2   Events 
    
   None 
    
E.3.3   Signals 
    
   Play tone 
      SignalID: pt (0x0001) 
       
      Plays audio tone over an audio channel 
       
      Signal Type: Brief 
       
      Duration: Provisioned 
       
      Additional Parameters: 
         Tone id list 
            ParameterID: tl (0x0001) 
             
            Type: list of tone ids.  
             
            List of tones to be played in sequence. The list  SHALL 
            contain one or more tone ids. 
            
         Inter signal duration 
            ParameterID: ind (0x0002) 
             
            Type: integer.  
             
            Timeout between two consecutive tones in milliseconds 
    
   No tone ids are specified in this package. Packages that extend this 
   package can add possible values for tone id as well as adding 
   individual tone signals 
     
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E.3.4   Statistics 
    
   None 
    
E.3.5   Procedures 
    
   None 
    
    
E.4     Tone Detection Package 
    
   PackageID: tonedet (0x0004) 
   Version: 1 
   Extends: None 
    
   This Package defines events for audio tone detection. Tones are 
   selected by name (tone id). MGs are expected to be provisioned with 
   the characteristics of appropriate tones for the country in which 
   the MG is located.  
    
   This package does not specify parameter values. It is intended to be 
   extendable.  
    
E.4.1   Properties 
    
   None 
    
E.4.2   Events 
    
   Start tone detected 
    
      EventID: std, 0x0001 
       
      Detects the start of a tone. The characteristics of positive tone 
      detection is implementation dependent. 
       
      EventsDescriptor parameters: 
         
         Tone id list 
            ParameterID: tl (0x0001) 
             
            Type:  list of tone ids 
             
            Possible values: The only tone id defined in this package 
            is "wild card" which is "*" in text encoding and 0x0000 in 
            binary. Extensions to this package would add possible 
            values for tone id. If tl is "wild card", any tone id is 
            detected 
         
      ObservedEventsDescriptor parameters: 
         
         Tone id  
            ParameterID: tid (0x0003) 
     
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            Type: Enumeration 
             
            Possible values: "wildcard" as defined above is the only 
            value defined in this package. Extensions to this package 
            would add additional possible values for tone id 
    
   End tone detected 
    
      EventID: etd, 0x0002 
       
      Detects the end of a tone. 
       
      EventDescriptor parameters: 
       
         Tone id list 
            ParameterID: tl (0x0001) 
             
            Type: enumeration or list of enumerated types 
             
            Possible values: No possible values are specified in this 
            package. Extensions to this package would add possible 
            values for tone id 
       
      ObservedEventsDescriptor parameters: 
       
         Tone id 
            ParameterID: tid (0x0003) 
             
            Type: Enumeration 
             
            Possible values: "wildcard" as defined above is the only 
            value defined in this package. Extensions to this package 
            would add possible values for tone id 
          
         Duration 
            ParameterId: dur (0x0002) 
             
            Type: integer, in milliseconds 
             
            This parameter contains the duration of the tone from first 
            detection until it stopped. 
       
   Long tone detected 
    
      EventID: ltd, 0x0003 
       
      Detects that a tone has been playing for at least a certain 
      amount of time 
       
      EventDescriptor parameters: 
       
         Tone id list 
            ParameterID: tl (0x0001) 
     
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            Type: enumeration or list 
             
            Possible values: "wildcard" as defined above is the only 
            value defined in this package. Extensions to this package 
            would add possible values for tone id 
          
         Duration 
            ParameterID: dur (0x0002) 
             
            Type: integer, duration to test against 
             
            Possible values: any legal integer, expressed in 
            milliseconds 
          
      ObservedEventsDescriptor parameters: 
          
         Tone id  
            ParameterID: tid (0x0003) 
             
            Possible values: No possible values are specified in this 
            package. Extensions to this package would add possible 
            values for tone id 
    
E.4.3   Signals 
    
   None 
    
E.4.4   Statistics 
    
   None 
    
E.4.5   Procedures 
    
   None 
    
    
E.5     Basic DTMF Generator Package 
    
   PackageID: dg (0x0005) 
   Version: 1 
   Extends: tonegen version 1 
    
   This package defines the basic DTMF tones as signals and extends the 
   allowed values of parameter tl of playtone in tonegen.  
    
E.5.1   Properties 
    
   None 
    
E.5.2   Events 
    
   None 
    
     
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E.5.3   Signals 
    
   dtmf character 0 
    
      SignalID: d0 (0x0010) 
       
      Generate DTMF 0 tone. The physical characteristic of DTMF 0 is 
      defined in the gateway.  
       
      Signal Type: Brief 
       
      Duration: Provisioned 
       
      Additional Parameters: 
      None  
    
   Additional Values: 
      d0 (0x0010) is defined as a toneid for playtone 
       
      The other dtmf characters are specified in exactly the same way. 
      A table with all signal names and signal IDs is included.  Note 
      that each dtmf character is defined as both a signal and a 
      toneid, thus extending the basic tone generation package.  Also 
      note that dtmf SignalIds are different from the names used in a 
      digit map. 
       
         Signal Name            Signal ID/tone id 
         dtmf character 0       d0 (0x0010) 
         dtmf character 1       d1 (0x0011) 
         dtmf character 2       d2 (0x0012) 
         dtmf character 3       d3 (0x0013) 
         dtmf character 4       d4 (0x0014) 
         dtmf character 5       d5 (0x0015) 
         dtmf character 6       d6 (0x0016) 
         dtmf character 7       d7 (0x0017) 
         dtmf character 8       d8 (0x0018) 
         dtmf character 9       d9 (0x0019) 
         dtmf character *       ds (0x0020) 
         dtmf character #       do (0x0021) 
         dtmf character A       da (0x001a) 
         dtmf character B       db (0x001b) 
         dtmf character C       dc (0x001c) 
         dtmf character D       dd (0x001d) 
    
E.5.4   Statistics 
    
   None 
    
E.5.5   Procedures 
    
   None 
    
    
     
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E.6     DTMF detection Package 
    
   PackageID: dd (0x0006) 
   Version: 1 
   Extends: tonedet version 1 
    
   This package defines the basic DTMF tones detection. This Package 
   extends the possible values of tone id in the "start tone detected" 
   "end tone detected" and "long tone detected" events. 
    
   Additional tone id values are all tone ids described in package dg 
   (basic DTMF generator package).  
    
   The following table maps DTMF events to digit map symbols as 
   described in section 7.1.14. 
       
         DTMF       Event Symbol 
                  
         d0                  "0" 
         d1                  "1" 
         d2                  "2" 
         d3                  "3" 
         d4                  "4" 
         d5                  "5" 
         d6                  "6" 
         d7                  "7" 
         d8                  "8" 
         d9                  "9" 
         da           "A" or "a" 
         db           "B" or "b" 
         dc           "C" or "c" 
         dd           "D" or "d" 
         ds           "E" or "e" 
         do           "F" or "f" 
    
    
E.6.1   Properties 
    
   None 
    
E.6.2   Events 
    
   DTMF digits 
    
      EventIds are defined with the same names as the SignalIds defined 
      in the table found in section E.5.3 
    
   DigitMap Completion Event 
    
      EventID: ce, 0x0004 
    
      Generated when a digit map completes as described in section 
      7.1.14. 
     
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      EventsDescriptor parameters: None. 
    
      ObservedEventsDescriptor parameters: 
    
         DigitString 
    
            ParameterID: ds (0x0001) 
    
            Type: string of digit map symbols (possibly empty) returned 
            as a quotedString 
    
            Possible values: a sequence of the characters "0" through 
            "9", "A" through "F", and the long duration modifier "Z". 
    
            Description: the portion of the current dial string as 
            described in section 7.1.14 which matched part or all of an 
            alternative event sequence specified in the digit map. 
    
         Termination Method 
    
            ParameterID:    Meth (0x0003) 
    
            Type: enumeration 
    
            Possible values: 
               "UM" (0x0001) Unambiguous match 
               "PM" (0x0002) Partial match, completion by timer expiry 
                              or unmatched event 
               "FM" (0x0003) Full match, completion by timer expiry or 
                              unmatched event 
       
            Description: indicates the reason for generation of the 
            event.  See the procedures in section 7.1.14. 
    
E.6.3   Signals 
    
   None 
    
E.6.4   Statistics 
    
   None 
    
E.6.5   Procedures 
    
   Digit map processing is activated only if an events descriptor is 
   activated that contains a digit map completion event as defined in 
   Section E.6.2 and that digit map completion event contains an 
   eventDM field in the requested actions as defined in Section 7.1.9.  
   Other parameters such as KeepActive or embedded events of signals 
   descriptors may also be present in the events descriptor and do not 
   affect the activation of digit map processing. 
    
    
     
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E.7     Call Progress Tones Generator Package 
    
   PackageID: cg, 0x0007 
   Version: 1 
   Extends: tonegen version 1 
    
   This package defines the basic call progress tones as signals and 
   extends the allowed values of the tl parameter of playtone in 
   tonegen .  
    
E.7.1   Properties 
    
   None 
    
E.7.2   Events 
    
   None 
    
E.7.3   Signals 
    
   Dial Tone 
      SignaID: dt (0x0030) 
    
      Generate dial tone. The physical characteristic of dial tone is 
      available in the gateway. 
    
      Signal Type: Timeout 
    
      Duration: Provisioned 
    
      Additional Parameters: 
         None  
    
      Additional Values 
         dt (0x0030) is defined as a tone id for playtone 
    
         The other tones of this package are defined in exactly the 
         same way. A table with all signal names and  signal IDs is 
         included.  Note that each tone is defined as both a signal and 
         a toneid, thus extending the basic tone generation package. 
    
            Signal Name                        Signal ID/tone id 
            Dial Tone                          dt (0x0030) 
            Ringing Tone                       rt (0x0031) 
            Busy Tone                          bt (0x0032) 
            Congestion Tone                    ct (0x0033) 
            Special Information Tone           sit(0x0034) 
            Warning Tone                       wt (0x0035) 
            Payphone Recognition Tone          prt (0x0036) 
            Call Waiting Tone                  cw (0x0037) 
            Caller Waiting Tone                cr (0x0038) 
    
     
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E.7.4   Statistics 
    
   None 
    
E.7.5   Procedures 
    
   NOTE - The required set of tone ids corresponds to those defined in 
   Recommendation E.180/Q.35 [ITU-T Recommendation E.180/Q.35 (1998)].  
   See E.180 for definition of the meanings of these tones.  
    
    
E.8     Call Progress Tones Detection Package 
    
   PackageID: cd (0x0008) 
   Version: 1 
   Extends: tonedet version 1 
    
   This package defines the basic call progress detection tones. This 
   Package extends the possible values of tone id in the "start tone 
   detected", "end tone detected" and "long tone detected" events.  
    
   Additional values 

      tone id values are defined for start tone detected, end tone 
      detected and long tone detected with the same values as those in 
      package cg (call progress tones generation package). 
    
      The required set of tone ids corresponds to Recommendation 
      E.180/Q.35 [ITU-T Recommendation E.180/Q.35 (1998)].  See 
      Recommendation E.180/Q.35 for definition of the meanings of these 
      tones.   
    
E.8.1   Properties 
    
   none 
    
E.8.2   Events 
    
   Events are defined as in the call progress tones generator package 
   (cg) for the tones listed in the table of section E.7.3 
    
E.8.3   Signals 
    
   none 
    
E.8.4   Statistics 
    
   none 
    
E.8.5   Procedures 
    
   none 
    
    
     
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E.9     Analog Line Supervision Package 
    
   PackageID: al, 0x0009 
   Version: 1 
   Extends: None 
    
   This package defines events and signals for an analog line.  
    
E.9.1   Properties 
    
   None 
    
E.9.2   Events 
    
   onhook 
    
      EventID: on (0x0004) 
    
      Detects handset going on hook. Whenever an events descriptor is 
      activated that requests monitoring for an on-hook event and the 
      line is already on-hook, then the MG shall behave according to 
      the setting of the "strict" parameter. 
    
      EventDescriptor parameters 
    
         Strict Transition 
    
            ParameterID: strict (0x0001) 
    
            Type: enumeration 
    
            Possible values: "exact" (0x00), "state" (0x01), 
            "failWrong" (0x02) 
    
               "exact" means that only an actual hook state transition 
               to on-hook is to be recognized; 
    
               "state" means that the event is to be recognized either 
               if the hook state transition is detected or if the hook 
               state is already on-hook; 
    
               "failWrong" means that if the hook state is already on-
               hook, the command fails and an error is reported. 
    
      ObservedEventsDescriptor parameters 
    
         Initial State 
    
            ParameterID: init (0x0002) 
    
            Type: Boolean 
    
            Possible values:  
    
     
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               True means that the event was reported because the line 
               was already on-hook when the events descriptor 
               containing this event was activated; 
    
               False means that the event represents an actual state 
               transition to on-hook. 
    
   offhook 
    
      EventID: of (0x0005) 
    
      Detects handset going off hook. Whenever an events descriptor is 
      activated that requests monitoring for an off-hook event and the 
      line is already off-hook, then the MG shall behave according to 
      the setting of the "strict" parameter. 
    
      EventDescriptor parameters 
    
         Strict Transition 
    
            ParameterID: strict (0x0001) 
    
            Type: enumeration 
    
            Possible values: "exact" (0x00), "state" (0x01), 
            "failWrong" (0x02) 
    
            "exact" means that only an actual hook state transition to 
            off-hook is to be recognized; 
    
            "state" means that the event is to be recognized either if 
            the hook state transition is detected or if the hook state 
            is already off-hook; 
    
            "failWrong" means that if the hook state is already off-
            hook, the command fails and an error is reported. 
    
      ObservedEventsDescriptor parameters 
    
         Initial State 
    
            ParameterID: init (0x0002) 
    
            Type: Boolean 
    
            Possible values:  
    
            True means that the event was reported because the line was 
            already off-hook when the events descriptor containing this 
            event was activated; 
    
            False means that the event represents an actual state 
            transition to off-hook. 
    
     
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   flashhook 
    
      EventID: fl, 0x0006 
    
      Detects handset flash. A flash occurs when an onhook is followed 
      by an offhook between a minimum and maximum duration. 
    
      EventDescriptor parameters 
    
         Minimum duration 
    
            ParameterID: mindur (0x0004) 
    
            Type: integer in milliseconds 
    
            Default value is provisioned 
    
         Maximum duration 
    
            ParameterID: maxdur (0x0005) 
    
            Type: integer in milliseconds 
    
            Default value is provisioned 
    
      ObservedEventsDescriptor parameters 
    
         None 
    
E.9.3   Signals 
    
   ring 
    
      SignalID: ri, 0x0002 
    
      Applies ringing on the line 
    
      Signal Type: TimeOut 
    
      Duration: Provisioned 
    
      Additional Parameters: 
    
         Cadence 
    
            ParameterID: cad (0x0006) 
    
            Type: list of integers representing durations of 
            alternating on and off segments, constituting a complete 
            ringing cycle starting with an on. Units in milliseconds 
            Default is fixed or provisioned.  Restricted function MGs 
            may ignore cadence  values they are incapable of 
            generating. 
    
     
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         Frequency 
    
            ParameterID: freq (0x0007) 
    
            Type: integer in Hz 
    
            Default is fixed or provisioned.  Restricted function MGs 
            may ignore frequency  values they are incapable of 
            generating. 
    
E.9.4   Statistics 
    
   None 
    
E.9.5   Procedures 
    
   If the MGC sets an EventsDescriptor containing a hook state 
   transition event (on-hook or off-hook) with the "strict" (0x0001) 
   parameter set to "failWrong", and the hook state is already what the 
   transition implies, the execution of the command containing that 
   EventsDescriptor fails.  The MG SHALL include error code 540 
   "Unexpected initial hook state" in its reponse. 
    
E.9.6   Error Code 
    
   This package defines a new error code: 
      540 - Unexpected initial hook state 
    
   The procedure for use of this code is given in section E.9.5. 
    
    
E.10    Basic Continuity Package 
    
   PackageID: ct (0x000a) 
   Version: 1 
   Extends: None 
    
   This package defines events and signals for continuity test. The 
   continuity test includes provision of either a loopback or 
   transceiver functionality. 
    
E.10.1  Properties 
    
   None 
    
E.10.2  Events 
    
   Completion 
    
      EventID: cmp, 0x0005 
    
      This event detects test completion of continuity test. 
    
      EventDescriptor parameters 
     
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         None 
    
      ObservedEventsDescriptor parameters 
    
         Result 
    
            ParameterID: res (0x0008) 
    
            Type: Enumeration 
    
            Possible values: success (0x0001), failure (0x0000) 
    
E.10.3  Signals 
    
   Continuity test 
    
      SignalID: ct (0x0003) 
    
      Initiates sending of continuity test tone on the termination to 
      which it is applied. 
    
      Signal Type: TimeOut 
    
      Default value is provisioned 
    
      Additional Parameters: 
         None 
    
   Respond 
    
      SignalID: rsp (0x0004) 
    
      The signal is used to respond to a continuity test .  See section 
      E.10.5 for further explanation. 
    
      Signal Type: On/Off 
    
      Default duration is provisioned 
    
      Additional Parameters: 
         None. 
    
E.10.4  Statistics 
    
   None 
    
E.10.5  Procedures 
    
   When a MGC wants to initiate a continuity test, it sends a command 
   to the MG containing 
    
   ¹    a signals descriptor with the ct signal, and 
    
     
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   ¹    an events descriptor containing the cmp event. 
    
   Upon reception of a command containing the ct signal and cmp event, 
   the MG initiates the continuity test tone for the specified 
   termination.  If the return tone is detected and any other required 
   conditions are satisfied before the signal times out, the cmp event 
   shall be generated with the value of the result parameter equal to 
   success.  In all other cases, the cmp event shall be generated with 
   the value of the result parameter equal to failure. 
    
   When a MGC wants the MG to respond to a continuity test, it sends a 
   command to the MG containing a signals descriptor with the rsp 
   signal.  Upon reception of a command with the rsp signal, the MG 
   either applies a loopback or (for 2-wire circuits) awaits reception 
   of a continuity test tone.  In the loopback case, any incoming 
   information shall be reflected back as outgoing information.  In the 
   2-wire case, any time the appropriate test tone is received, the 
   appropriate response tone should be sent.  The MGC determines when 
   to remove the rsp signal. 
    
   When a continuity test is performed on a termination, no echo 
   devices or codecs shall be active on that termination. 
    
   Performing voice path assurance as part of continuity testing is 
   provisioned by bilateral agreement between network operators. 
    
   (Informative Note) Example tones and test procedure details are 
   given in Q.724 sections 7 and 8, Q.764 section 2.1.8 and Q.902.4. 
    
    
E.11    Network Package 
    
   PackageID: nt (0x000b) 
   Version: 1 
   Extends: None 
    
   This package defines properties of network terminations independent 
   of network type.  
    
E.11.1  Properties 
    
   Maximum Jitter Buffer 
    
      PropertyID: jit (0x0007) 
    
      This property puts a maximum size on the jitter buffer. 
    
      Type: integer in milliseconds 
    
      Possible Values: This property is specified in milliseconds. 
    
      Defined In: LocalControlDescriptor 
    
      Characteristics: read/write 
     
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E.11.2  Events 
  
   network failure 
    
      EventID: netfail, 0x0005 
    
      The termination generates this event upon detection of a failure 
      due to external or internal network reasons. 
    
      EventDescriptor parameters 
    
         None 
    
      ObservedEventsDescriptor parameters 
    
         cause 
    
            ParameterID: cs (0x0001) 
    
            Type: String 
    
            Possible values: any text string 
    
            This parameter may be included with the failure event to 
            provide diagnostic information on the reason of failure. 
    
   quality alert 
    
      EventID: qualert, 0x0006 
    
      This property allows the MG to indicate a loss of quality of the 
      network connection. The MG may do this by measuring packet loss, 
      interarrival jitter, propogation delay and then indicating this 
      using a percentage of quality loss.  
    
      EventDescriptor parameters 
    
         Threshold 
    
            ParameterId: th (0x0001) 
    
            Type: integer 
    
            Possible Values: threshold for percent of quality loss 
            measured, calculated based on a provisioned method, that 
            could take into consideration packet loss, jitter, and 
            delay for example.  Event is triggered when calculation 
            exceeds the threshold. 
    
      ObservedEventsDescriptor parameters 
    
         Threshold 
    
     
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            ParameterId: th (0x0001) 
    
            Type: integer 
    
            Possible Values: percent of quality loss measured, 
            calculated based on a provisioned method, that could take 
            into consideration packet loss, jitter, and delay for 
            example. 
    
E.11.3  Signals 
  
   none 
    
E.11.4  Statistics 
    
   Duration 
    
      StatisticsID: dur (0x0001) 
    
      Description: Provides duration of time the termination has been 
      in the context. 
    
      Type: Double, in milliseconds  
    
   Octets Sent 
    
      StatisticID: os (0x0002) 
    
      Type: double 
    
      Possible Values: any 64 bit integer  
    
   Octets Received 
    
      StatisticID: or (0x0003) 
    
      Type: double 
    
      Possible Values: any 64 bit integer  
    
E.11.5  Procedures 
    
   none 
    
    
E.12    RTP  Package 
    
   PackageID: rtp (0x000c) 
   Version: 1 
   Extends: Network Package version 1 
    
   This package is used to support packet based multimedia data 
   transfer by means of the Real-time Transport Protocol (RTP) [RFC 
   1889]. 
     
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E.12.1  Properties 
    
   None 
    
E.12.2  Events 
    
   Payload Transition 
    
     EventID: pltrans, 0x0001 
    
     This event detects and notifies when there is a transition of the 
     RTP payload format from one format to another. 
    
     EventDescriptor parameters 
    
        None 
    
     ObservedEventsDescriptor parameters 
    
        ParameterName: rtppayload 
    
           ParameterID: rtppltype, 0x01 
    
           Type: list of enumerated types. 
    
           Possible values: The encoding method shall be specified by 
           using one or several valid encoding names, as defined in the 
           RTP AV Profile or registered with IANA. 
    
E.12.3  Signals 
    
   None 
    
E.12.4  Statistics 
    
   Packets Sent 
    
      StatisticID: ps (0x0004) 
    
      Type: double 
    
      Possible Values: any 64 bit integer  
    
   Packets Received 
    
      StatisticID: pr (0x0005) 
    
      Type: double 
    
      Possible Values: any 64 bit integer  
    
   Packet Loss 
    
     
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      StatisticID: pl (0x0006) 
    
      Describes the current rate of packet loss on an RTP stream, as 
      defined in IETF RFC 1889. Packet loss is expressed as percentage 
      value: number of packets lost in the interval between two 
      reception reports, divided by the number of packets expected 
      during that interval. 
    
      Type: double 
    
      Possible Values: a 32 bit whole number and a 32 bit fraction. 
    
   Jitter 
    
      StatisticID: jit (0x0007) 
    
      Requests the current value of the interarrival jitter on an RTP 
      stream as defined in IETF RFC 1889. Jitter measures the variation 
      in interarrival time for RTP data packets. 
    
   Delay 
    
      StatisticID:delay (0x0008) 
    
      Requests the current value of packet propagation delay expressed 
      in timestamp units. Same as average latency. 
    
E.12.5  Procedures 
    
   none 
    
    
E.13    TDM Circuit  Package 
    
   PackageID: tdmc (0x000d) 
   Version: 1 
   Extends: Network Package version 1 
    
   This package is used to support TDM circuit terminations. 
    
E.13.1  Properties 
    
   Echo Cancellation 
    
     PropertyID: ec (0x0008) 
    
     Type: boolean 
    
     Possible Values: 
    
        "on" (when the echo cancellation is requested) and 
       
        "off" (when it is turned off.) 
    
     
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     The default is provisioned. 
    
     Defined In: LocalControlDescriptor 
    
     Characteristics: read/write 
    
   Gain Control 
    
     PropertyID: gain (0x000a) 
    
     Gain control, or usage of of signal level adaptation and noise 
     level reduction is used to adapt the level of the signal. However, 
     it is necessary, for example for modem calls, to turn off this 
     function. 
    
     Type: integer 
    
     Possible Values: 
    
     The gain control parameter may either be specified as "automatic" 
     (0xffffffff), or as an explicit number of decibels of gain (any 
     other integer value).  The default is provisioned in the MG. 
    
     Defined In: LocalControlDescriptor 
    
     Characteristics: read/write 
    
E.13.2  Events 
    
   none  
    
E.13.3  Signals 
    
   none 
    
E.13.4  Statistics 
    
   None 
    
E.13.5  Procedures 
    
   None 
    
     
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APPENDIX A      EXAMPLE CALL FLOWS (INFORMATIVE) 
    
   All H.248 implementors must read the normative part of this document 
   carefully before implementing from it. No one should use the 
   examples in this section as stand-alone explanations of how to 
   create protocol messages. 
    
   The examples in this section use SDP for encoding of the Local and 
   Remote stream descriptors. SDP is defined in RFC 2327. If there is 
   any discrepancy between the SDP in the examples, and RFC 2327, the 
   RFC should be consulted for correctness. Audio profiles used are 
   those defined in RFC 1890, and others registered with IANA. For 
   example, G.711 A-law is called PCMA in the SDP, and is assigned 
   profile 0. G.723 is profile 4, and H263 is profile 34. See also  
    
   http://www.isi.edu/in-notes/iana/assignments/rtp-parameters  
    
A.1     Residential Gateway to Residential Gateway Call 
    
   This example scenario illustrates the use of the elements of the 
   protocol to set up a Residential Gateway to Residential Gateway call 
   over an IP-based network.  For simplicity, this example assumes that 
   both Residential Gateways involved in the call are controlled by the 
   same Media Gateway Controller. 
    
A.1.1   Programming Residential GW Analog Line Terminations for Idle 
        Behavior 
    
   The following illustrates the API invocations from the Media Gateway 
   Controller and Media Gateways to get the Terminations in this 
   scenario programmed for idle behavior.  Both the originating and 
   terminating Media Gateways have idle AnalogLine Terminations 
   programmed to look for call initiation events (i.e.-offhook) by 
   using the Modify Command with the appropriate parameters.  The null 
   Context is used to indicate that the Terminations are not yet 
   involved in a Context. The ROOT termination is used to indicate the 
   entire MG instead of a termination within the MG. 
    
   In this example, MG1 has the IP address 124.124.124.222, MG2 is 
   125.125.125.111, and the MGC is 123.123.123.4. The default Megaco 
   port is 55555 for all three. 
    
   1.   An MG registers with an MGC using the ServiceChange command: 
    
   MG1 to MGC: 
   MEGACO/1 [124.124.124.222] 
   Transaction = 9998 { 
       Context = - { 
           ServiceChange = ROOT {Services { 
               Method=Restart,  
               ServiceChangeAddress=55555, Profile=ResGW/1} 
           } 
       } 
   } 
     
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   2.   The MGC sends a reply: 
    
   MGC to MG1: 
   MEGACO/1 [123.123.123.4]:55555 
   Reply = 9998 { 
      Context = - {ServiceChange = ROOT {  
        Services {ServiceChangeAddress=55555, Profile=ResGW/1} } } 
   } 
    
   3.   The MGC programs a Termination in the NULL context. The 
   terminationId is A4444, the streamId is 1, the requestId in the 
   Events descriptor is 2222. The   mId is the identifier of the sender 
   of this message, in this case, it is the IP address and port 
   [123.123.123.4]:55555. Mode for this stream is set to SendReceive. 
   Ÿal÷ is the analog line supervision package. 
    
   MGC to MG1: 
   MEGACO/1 [123.123.123.4]:55555 
   Transaction = 9999 { 
       Context = - { 
           Modify = A4444 { 
               Media { Stream = 1 {  
                        LocalControl { 
                            Mode = SendReceive,  
                            tdmc/gain=2,  ; in dB,  
                            tdmc/ec=on 
                        }, 
                        Local { 
   v=0 
   c=IN IP4 $ 
   m=audio $ RTP/AVP 0 
   a=fmtp:PCMU VAD=X-NNVAD ; special voice activity  
                           ; detection algorithm 
                        } 
                    } 
               }, 
               Events = 2222 {al/of}          
           } 
       } 
   } 
    
   The dialplan script could have been loaded into the MG previously.  
   Its function would be to wait for the OffHook, turn on dialtone and 
   start collecting DTMF digits. However in this example, we use the 
   digit map, which is put into place after the offhook is detected 
   (step 5 below).  
    
   Note that the embedded EventsDescriptor could have been used to 
   combine steps 3 and 4 with steps 8 and 9, eliminating steps 6 and 7. 
    
   4.   The MG1 accepts the Modify with this reply: 
    
   MG1 to MGC: 
     
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   MEGACO/1 [124.124.124.222]:55555 
   Reply = 9999 { 
      Context = - {Modify = A4444} 
   } 
    
   5.   A similar exchange happens between MG2 and the MGC, resulting 
   in an idle Termination called A5555. 
    
A.1.2   Collecting Originator Digits and Initiating Termination 
    
   The following builds upon the previously shown conditions.  It 
   illustrates the transactions from the Media Gateway Controller and 
   originating Media Gateway (MG1) to get the originating Termination 
   (A4444) through the stages of digit collection required to initiate 
   a connection to the terminating Media Gateway (MG2).  
    
   6.   MG1 detects an offhook event from User 1 and reports it to the 
   Media Gateway Controller via the Notify Command.  
    
   MG1 to MGC: 
   MEGACO/1 [124.124.124.222]:55555 
   Transaction = 10000 { 
      Context = - { 
          Notify = A4444 {ObservedEvents =2222 { 
            19990729T22000000:al/of}} 
      }  
   } 
    
   7.   And the Notify is acknowledged. 
    
   MGC to MG1: 
   MEGACO/1 [123.123.123.4]:55555 
   Reply = 10000 { 
       Context = - {Notify = A4444} 
   } 
    
   8.   The MGC Modifies the termination to play dial tone, to look for 
   digits according to Dialplan0 and to look for the on-hook event now.  
    
   MGC to MG1: 
   MEGACO/1 [123.123.123.4]:55555 
   Transaction = 10001 { 
       Context = - { 
           Modify = A4444 { 
               Events = 2223 { 
                   al/on, dd/ce {DigitMap=Dialplan0}            
               }, 
               Signals {cg/dt},  
               DigitMap= Dialplan0{ 
   (0| 00|[1-7]xxx|8xxxxxxx|Fxxxxxxx|Exx|91xxxxxxxxxx|9011x.)}    
           } 
       } 
   }  
    
     
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   9.   And the Modify is acknowledged. 
    
   MG1 to MGC: 
   MEGACO/1 [124.124.124.222]:55555 
   Reply = 10001 { 
       Context = - {Modify = A4444} 
   } 
    
   10.  Next, digits are accumulated by MG1 as they are dialed by User 
   1.  Dialtone is stopped upon detection of the first digit. When an 
   appropriate match is made of collected digits against the currently 
   programmed Dialplan for A4444, another Notify is sent to the Media 
   Gateway Controller.  
    
   MG1 to MGC: 
   MEGACO/1 [124.124.124.222]:55555 
   Transaction = 10002 { 
      Context = - { 
          Notify = A4444 {ObservedEvents =2223 { 
            19990729T22010001:dd/ce{ds="916135551212",Meth=FM}}} 
      }  
   } 
    
   11.  And the Notify is acknowledged. 
    
   MGC to MG1: 
   MEGACO/1 [123.123.123.4]:55555 
   Reply = 10002 { 
       Context = - {Notify = A4444} 
   } 
    
   12.  The controller then analyses the digits and determines that a 
   connection needs to be made from MG1 to MG2. Both the TDM 
   termination A4444, and an RTP termination are added to a new context 
   in MG1. Mode is ReceiveOnly since Remote descriptor values are not 
   yet specified. Preferred codecs are in the MGC's preferred order of 
   choice. 
    
   MGC to MG1: 
   MEGACO/1 [123.123.123.4]:55555 
   Transaction = 10003 { 
       Context = $ { 
          Add = A4444,  
          Add = $ { 
              Media {  
                Stream = 1 {  
                     LocalControl {                            
                         Mode = ReceiveOnly,  
    
                         nt/jit=40 ; in ms 
                     }, 
                     Local { 
   v=0                                
   c=IN IP4 $                                
     
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   m=audio $ RTP/AVP 4 
   a=ptime:30 
   v=0                                
   c=IN IP4 $                                
   m=audio $ RTP/AVP 0 
                     } 
                } 
             }     
          } 
       } 
   }   
    
   NOTE - The MGC states its preferred parameter values as a series of 
   sdp blocks in  Local. The MG fills in the Local Descriptor in the 
   Reply. 
    
   13.  MG1 acknowledges the new Termination and fills in the Local IP 
   address and UDP port. It also makes a choice for the codec based on 
   the MGC preferences in Local. MG1 sets the RTP port to 2222. 
    
   MEGACO/1 [124.124.124.222]:55555 
   Reply = 10003 { 
      Context = 2000 {  
         Add = A4444, 
         Add=A4445{ 
            Media {  
                Stream = 1 { 
                    Local { 
   v=0                                
   c=IN IP4 124.124.124.222                                
   m=audio 2222 RTP/AVP 4 
   a=ptime:30 
   a=recvonly 
                    } ; RTP profile for G.723 is 4 
                } 
            } 
         } 
      } 
   } 
    
   14.  The MGC will now associate A5555 with a new Context on MG2, and 
   establish an RTP Stream (i.e, A5556 will be assigned), SendReceive 
   connection through to the originating user, User 1. The MGC also 
   sets ring on A5555. 
    
   MGC to MG2: 
   MEGACO/1 [123.123.123.4]:55555 
   Transaction = 50003 { 
       Context = $ {  
          Add = A5555  { Media {  
               Stream = 1 {  
                    LocalControl {Mode = SendReceive} }}, 
                Events=1234{al/of},  
               Signals {al/ri} 
     
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               }, 
          Add  = $ {Media {  
               Stream = 1 {  
                    LocalControl {   
                       Mode = SendReceive, 
                       nt/jit=40 ; in ms 
                    }, 
                    Local { 
   v=0 
   c=IN IP4 $  
   m=audio $ RTP/AVP 4  
   a=ptime:30 
                    }, 
                    Remote { 
   v=0 
   c=IN IP4 124.124.124.222  
   m=audio 2222 RTP/AVP 4  
   a=ptime:30 
                    } ; RTP profile for G.723 is 4  
                } 
             } 
         } 
      } 
   } 
    
   15.  This is acknowledged. The stream port number is different from 
   the control port number. In this case it is 1111 (in the SDP). 
    
   MG2 to MGC: 
   MEGACO/1 [124.124.124.222]:55555 
   Reply = 50003 { 
      Context = 5000 { 
        Add = A5555, 
         Add = A5556{ 
            Media {  
               Stream = 1 {  
                   Local { 
   v=0 
   c=IN IP4 125.125.125.111  
   m=audio 1111 RTP/AVP 4 
   }  
               } ; RTP profile for G723 is 4 
            } 
          } 
      } 
   } 
    
   16.  The above IPAddr and UDPport need to be given to MG1 now.  
    
   MGC to MG1: 
   MEGACO/1 [123.123.123.4]:55555 
   Transaction = 10005 { 
     Context = 2000 { 
       Modify = A4444 { 
     
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         Signals {cg/rt} 
       }, 
       Modify = A4445 { 
          Media {  
               Stream = 1 {  
                   Remote { 
   v=0 
   c=IN IP4 125.125.125.111  
   m=audio 1111 RTP/AVP 4 
                   }  
               } ; RTP profile for G723 is 4 
           } 
       } 
     } 
   } 
    
   MG1 to MGC: 
   MEGACO/1 [124.124.124.222]:55555 
   Reply = 10005 { 
      Context = 2000 {Modify = A4444, Modify = A4445} 
   } 
    
   17.  The two gateways are now connected and User 1 hears the 
   RingBack. The MG2 now waits until User2 picks up the receiver and 
   then the two-way call is established. 
    
   From MG2 to MGC: 
    
   MEGACO/1 [125.125.125.111]:55555 
   Transaction = 50005 { 
      Context = 5000 { 
          Notify = A5555 {ObservedEvents =1234 { 
            19990729T22020002:al/of}} 
      }  
   } 
    
   From MGC to MG2: 
    
   MEGACO/1 [123.123.123.4]:55555 
   Reply = 50005 { 
       Context = - {Notify = A5555} 
   } 
    
   From MGC to MG2: 
    
   MEGACO/1 [123.123.123.4]:55555 
   Transaction = 50006 { 
      Context = 5000 { 
         Modify = A5555 { 
            Events = 1235 {al/on}, 
            Signals { } ; to turn off ringing  
         } 
      } 
   } 
     
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   From MG2 to MGC: 
    
   MEGACO/1 [125.125.125.111]:55555 
   Reply = 50006 { 
    Context = 5000 {Modify = A4445} 
   } 
    
   18.  Change mode on MG1 to SendReceive, and stop the ringback. 
    
   MGC to MG1: 
   MEGACO/1 [123.123.123.4]:55555 
   Transaction = 10006 { 
      Context = 2000 { 
         Modify = A4445 { 
            Media {  
               Stream = 1 {  
                  LocalControl { 
                     Mode=SendReceive 
                  }  
               } 
            } 
         }, 
         Modify = A4444 { 
            Signals { } 
         }         
      } 
   } 
    
   from MG1 to MGC: 
   MEGACO/1 [124.124.124.222]:55555 
   Reply = 10006 { 
      Context = 2000 {Modify = A4445, Modify = A4444}} 
    
   19.  The MGC decides to Audit the RTP termination on MG2. 
    
   MEGACO/1 [123.123.123.4]:55555 
   Transaction = 50007 { 
      Context = - {AuditValue = A5556{  
         Audit{Media, DigitMap, Events, Signals, Packages, Statistics 
   }} 
      }   
   } 
    
   20.  The MG2 replies. 
    
   MEGACO/1 [125.125.125.111]:55555 
   Reply = 50007 { 
      Context = - { 
   AuditValue = A5556 { 
             Media {  
                TerminationState { ServiceStates = InService, 
                        Buffer = OFF },  
                 Stream = 1 {  
     
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                    LocalControl { Mode = SendReceive, 
                       nt/jit=40 }, 
                    Local { 
   v=0 
   c=IN IP4 125.125.125.111  
   m=audio 1111 RTP/AVP  4  
   a=ptime:30 
                   }, 
                    Remote { 
   v=0 
   c=IN IP4 124.124.124.222  
   m=audio 2222 RTP/AVP  4 
   a=ptime:30   
                    } } }, 
              Events, 
             Signals, 
             DigitMap, 
            Packages {nt-1, rtp-1}, 
             Statistics { rtp/ps=1200,  ; packets sent 
                          nt/os=62300, ; octets sent 
                          rtp/pr=700, ; packets received 
                          nt/or=45100, ; octets received 
                          rtp/pl=0.2,  ; % packet loss  
                          rtp/jit=20, 
                          rtp/delay=40 } ; avg latency  
          } 
       }     
   } 
    
   21.  When the MGC receives an onhook signal from one of the MGs, it 
   brings down the call. In this example, the user at MG2 hangs up 
   first. 
    
   From MG2 to MGC: 
    
   MEGACO/1 [125.125.125.111]:55555 
   Transaction = 50008 { 
      Context = 5000 { 
          Notify = A5555 {ObservedEvents =1235 { 
             19990729T24020002:al/on} 
          } 
      }  
   } 
    
   From MGC to MG2: 
    
   MEGACO/1 [123.123.123.4]:55555 
   Reply = 50008 { 
       Context = - {Notify = A5555} 
   } 
    
   22.  The MGC now sends both MGs a Subtract to take down the call. 
   Only the subtracts to MG2 are shown here. Each termination has its 
   own set of statistics that it gathers. An MGC may not need to 
     
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   request both to be returned. A5555 is a physical termination, and 
   A5556 is an RTP termination. 
    
   From MGC to MG2: 
    
   MEGACO/1 [123.123.123.4]:55555 
   Transaction = 50009 { 
      Context = 5000 { 
         Subtract = A5555 {Audit{Statistics}}, 
         Subtract = A5556 {Audit{Statistics}} 
      } 
   } 
    
   From MG2 to MGC: 
    
   MEGACO/1 [125.125.125.111]:55555 
   Reply = 50009 { 
      Context = 5000 { 
        Subtract = A5555 { 
             Statistics {  
                nt/os=45123, ; Octets Sent 
                nt/dur=40 ; in seconds 
                } 
          }, 
          Subtract = A5556 { 
             Statistics { 
                rtp/ps=1245, ; packets sent 
                nt/os=62345, ; octets sent 
                rtp/pr=780, ; packets received 
                nt/or=45123, ; octets received 
                rtp/pl=10, ;  % packets lost 
                rtp/jit=27, 
                rtp/delay=48 ; average latency 
             } 
          } 
      } 
   } 
    
   23.  The MGC now sets up both MG1 and MG2 to be ready to detect the 
   next off-hook event. See step 1. Note that this could be the default 
   state of a termination in the null context, and if this were the 
   case, no message need be sent from the MGC to the MG. Once a 
   termination returns to the null context, it goes back to the default 
   termination values for that termination. 
     
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References 
    
   See section 2 above. 
    
    
    
Author's Address 
    
   Marcello Pantaleo          Phone:  +49 2407 575 4806 
   Ericsson                   Email:  Marcello.Pantaleo@eed.ericsson.se 
    
    
    
     
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