Dispatch Working Group A. Allen, Ed.
Internet-Draft Research in Motion (RIM)
Intended status: Informational January 10, 2012
Expires: July 13, 2012
Using the International Mobile station Equipment Identity(IMEI)URN as an
Instance ID
draft-allen-dispatch-imei-urn-as-instanceid-04
Abstract
This specification defines how the Uniform Resource Name namespace
reserved for GSMA (Global Sstandard for Mobiles Association)
identities and its sub namespace for the IMEI (International Mobile
station Equipment Identity) can be used as an instance-id as
specified in RFC 5626 [1] and also as used by RFC 5627 [2].
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. User Agent Client Procedures . . . . . . . . . . . . . . . . . 5
5. User Agent Server Procedures . . . . . . . . . . . . . . . . . 6
6. Security considerations . . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative references . . . . . . . . . . . . . . . . . . . 7
8.2. Informative references . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
This specification defines how the Uniform Resource Name namespace
reserved for GSMA identities and its sub namespace for the IMEI
(International Mobile station Equipment Identity) as defined in
draft-montemurro-gsma-imei-urn-09 [3] can be used as an instance-id
as specified in RFC 5626 [1] and also as used by RFC 5627 [2].
RFC 5626 [1] defines the "+sip.instance" Contact header field
parameter which contains a URN as per RFC 2141 [4] defined as an
instance-id that uniquely identifies a specific UA instance. This
instance-id is used as defined in RFC 5626 [1] so that registrar can
recognize that the contacts from multiple registrations correspond to
the same UA. The instance-ID is also used as defined by RFC 5627 [2]
to create Globally Routable User Agent URIs (GRUUs) that can be used
to uniquely address a UA when multiple UAs are registered with the
same Address of Record (AoR).
RFC 5626 [1] defines that a UA SHOULD create a Universally Unique
Identifier (UUID) URN as defined in RFC 4122 [6] as its instance-id
but allows for the possibility of other URN schemes to be used. If a
URN scheme other than UUID is used, the UA MUST only use URNs for
which an RFC (from the IETF stream) defines how the specific URN
needs to be constructed and used in the "+sip.instance" Contact
header field parameter for outbound behavior. This specification
meets this requirement by specifying how the GSMA IEMEI URN is used
in the "+sip.instance" Contact header field parameter for outbound
behavior and draft-montemurro-gsma-imei-urn-09 [3] defines how the
GSMA IMEI URN is constructed
The GSMA IMEI is an identifier for a namespace for the IMEI a
globally unique identifier that identifies Mobile Equipment used in
Global System for Mobile (GSM), Universal Mobile Telecommunications
System (UMTS) and 3GPP LTE (Long Term Evolution)networks. The IMEI
allocation is managed by the GSMA to ensure that the IMEI values are
globally unique. Details of the formatting of the IMEI as a URN are
defined in draft-montemurro-gsma-imei-urn-09 [3] and the definition
of the IMEI is contained in 3GPP TS 23.003 [7]. Further details
about the GSMA role in allocating the IMEI and the IMEI allocation
guidelines can be found in GSMA PRD DG.06 [8]
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [5].
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3. Background
GSM and UMTS capable mobile devices represent 90% of the mobile
devices in use worldwide. GSM and UMTS mobile devices each have an
IMEI allocated which uniquely identifies the mobile device from all
other GSM/UMTS mobile devices deployed. Amongst other things in some
regulatory jurisdictions the IMEI is used to identify a stolen mobile
is being used and help to identify the subscription that is using it
and to prevent its use. Whilst GSM was originally a circuit switched
system enhancements such as GPRS (General Packet Radio Service) and
UMTS have added IP data capabilities which along with the definition
of the IP Multimedia Subsystem (IMS) has made SIP based calls and IP
multimedia sessions from mobile devices possible. The latest
enhancment known as LTE will introduce even higher data rates and
dispenses with the circuit switched domain completely meaning that
with LTE voice calls will need to be conducted using IP and IMS.
However, the transition to all IP, SIP based IMS networks worldwide
will take a great many years and mobile devices being mobile will
need to operate in both IP/SIP/IMS mode and circuit switched mode.
In fact calls and sessions will need to be handed over between IP/
SIP/IMS mode and circuit switched mode during a call. Also as many
existing GSM and UMTS radio access networks are unable to support IP/
SIP/IMS based voice services in a commercially acceptable manner some
sessions can have some media types delivered via IP/IMS
simultaneously with voice media delivered via circuit switched with
the same mobile device simultaneously attached via both the IP/SIP/
IMS domain and the circuit switched domain. To meet this need 3GPP
has specified how to maintain session continuity between the IP/SIP/
IMS domain and the circuit switched domain in 3GPP TS 24.237 [9] and
how to access IMS hosted services via both the IP/SIP/IMS domain and
the circuit switched domain in 3GPP TS 24.292 [10].
In order for the the mobile device to access SIP/IMS services via the
circuit switched domain 3GPP has defined a MSC (Mobile Switching
Center) server enhanced for ICS which controls mobile voice call
setup over the circuit switched radio access while establishing the
corresponding voice session in the core network using SIP/IMS. To
enable this the MSC server enhanced for ICS (IMS centralized
services) performs SIP registration on behalf of the mobile device
which can be simultaneously also directly registered with the IP/SIP/
IMS domain. The SIP/IMS network needs to be able to identify that
both of these SIP registrations are from the same UA instance and
also correctly handle sessions establishment requests addressed using
GRUUs as defined in RFC 5627 [2] when the mobile device is attached
using the circuit switched domain. The only mobile device identifier
that is transportable using GSM/UMTS/LTE signaling is the IMEI
therefore the instance-id used by the MSC server enhanced for ICS
when registering on behalf of the mobile device and the instance-id
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when the mobile device registers directly needs to be based on the
IMEI.
Additionally in order to meet the regulatory requirements to use the
IMEI to identify a stolen mobile is being used and help to identify
the subscription that is using it and to prevent its use the same
IMEI that is obtained from the circuit switched signaling needs to be
obtainable from SIP signaling.
3GPP TS 24.237 [9] and 3GPP TS 24.292 [10] already define the use of
the URN namespace for the GSMA and IMEI as defined in
draft-montemurro-gsma-imei-urn-09 [3] as the instance-id used by
mobile devices and the MSC server enhanced for ICS for SIP/IMS
registrations for these reasons.
4. User Agent Client Procedures
A UAC that has an IMEI as defined in 3GPP TS 23.003 [7] that is
registering with a 3GPP IMS network MUST include in the
"sip.instance" media feature tag the GSMA IMEI URN according to the
syntax defined in draft-montemurro-gsma-imei-urn-09 [3] when
performing the registration procedures defined in RFC 5626 [1] or RFC
5627 [2] or any other procedure requiring including the
"sip.instance" media feature tag. The UAC SHOULD NOT include the
optional "svn" parameter in the GSMA IMEI URN in the "sip.instance"
media feature tag, since the software version can change as a result
of upgrades to the device firmware which would create a new instance
ID. The UAC MUST provide lexically equivalent URNs in each
registration [1]. Hence, any optional or variable components of the
URN (e.g., the "vers" parameter) MUST be presented with the same
values and in the same order in every registration as in the first
registration.
A UAC MUST only use the GSMA IMEI URN as an Instance ID when
registering with a 3GPP IMS network. When registering with a non
3GPP IMS network a UAC SHOULD use a UUID as an Instance ID as defined
in RFC 5626 [1].
A UAC SHOULD NOT include its "sip.instance" media feature tag
containing the GSMA IMEI URN in the Contact header field of non-
register requests unless the UAC is certain that the request will be
sent via a trusted intermediary that will remove the "sip.instance"
media feature tag prior to forwarding the request towards the
destination. In order to ensure that all requests containing the
"sip.instance" media feature tag are forwarded via the trusted
intermediary the UAC MUST first have verified that the trusted
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intermediary is present (e.g. first contacted via a registration or
configuration procedure). The exception to this is when the request
is related to an emergency session when regulatory requirements can
require the IMEI to be provided to the Public Safety Answering Point
(PSAP).
5. User Agent Server Procedures
A UAS SHOULD NOT include its "sip.instance" media feature tag
containing the GSMA IMEI URN in the Contact header field of responses
unless the UAS is certain that the response will be sent via a
trusted intermediary that will remove the "sip.instance" media
feature tag prior to forwarding the response towards the destination.
In order to ensure that all responses containing the "sip.instance"
media feature tag are forwarded via the trusted intermediary the UAS
MUST first have verified that the trusted intermediary is present
(e.g. first contacted via a registration or configuration procedure).
The exception to this is when the response is related to an emergency
session when regulatory requirements can require the IMEI to be
provided to the Public Safety Answering Point(PSAP).
6. Security considerations
Because IMEIs can be loosely correlated to a user, they need to be
treated as any other personally identifiable information. In
particular, the "sip.instance" media feature tag containing the GSMA
IMEI URN SHOULD NOT be included in requests or responses intended to
convey any level of anonymity. Publication of the GSMA IMEI URN to
networks that the UA is not attached to or the UA does not have a
service relationship with is a security breach and the "sip.instance"
media feature tag SHOULD NOT be forwarded by the service provider's
network elements when forwarding requests or responses towards the
destination UA.
In order to protect from tampering the REGISTER requests containing
the GSMA IMEI URN SHOULD be sent using a security mechanism such as
TLS [11] (or another security mechanism that provides equivalent
levels of protection).
7. Acknowledgements
The author would like to thank Paul Kyzivat, Dale Worley, Cullen
Jennings, Adam Roach, and Keith Drage for reviewing this draft and
providing their comments.
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8. References
8.1. Normative references
[1] Jennings, C., Mahy, R., and F. Audet, "Managing Client-
Initiated Connections in the Session Initiation Protocol
(SIP)", RFC 5626, October 2009.
[2] Rosenberg, J., "Obtaining and Using Globally Routable User
Agent URIs (GRUUs) in the Session Initiation Protocol (SIP)",
RFC 5627, October 2009.
[3] Montemurro, M., "A Uniform Resource Name Namespace For The GSM
Association (GSMA) and the International Mobile station
Equipment Identity(IMEI), work in progress", Internet
Draft draft-montemurro-gsma-imei-urn-09, January 2012.
[4] Moats, R., "URN Syntax", RFC 2141, May 1997.
[5] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
8.2. Informative references
[6] Leach, P., Mealling, M., and R. Salz, "A Universally Unique
IDentifier (UUID) URN Namespace", RFC 4122, July 2005.
[7] 3GPP, "TS 23.003: Numbering, addressing and identification
(Release 8)", 3GPP 23.003, September 2008,
.
[8] GSMA Association, "IMEI Allocation and Approval Guidelines",
PRD TS.06 (DG06) version 6.0, July 2011, .
[9] 3GPP, "TS 24.237: Mobile radio interface Layer 3 specification;
Core network protocols; Stage 3 (Release 8)", 3GPP 24.237,
March 2009,
.
[10] 3GPP, "TS 24.292: IP Multimedia (IM) Core Network (CN)
subsystem Centralized Services (ICS); Stage 3 (Release 8)",
3GPP 24.292, March 2009,
.
[11] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
RFC 2246, January 1999.
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Author's Address
Andrew Allen (editor)
Research in Motion (RIM)
1200 Sawgrass Corporate Parkway
Sunrise, Florida 33323
USA
Phone: unlisted
Fax: unlisted
Email: aallen@rim.com
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