Network Working Group S. Jiang Internet-Draft F. Xia Intended status: Standards Track B. Sarikaya Expires: May 24, 2012 Huawei Technologies November 21, 2011 Prefix Assignment in DHCPv6 draft-ietf-dhc-host-gen-id-01.txt Abstract This document describes a procedure for configuring hosts' IPv6 address which the prefix is assigned from a DHCPv6 server through DHCPv6 protocol while the interface identifiers are independently generated by the hosts. The method is applicable to Cryptographically Generated Addresses (CGA), and other IPv6 addresses with host-generated interface identifiers. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on May 24, 2012. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of Jiang, et al. Expires May 24, 2012 [Page 1] Internet-Draft Prefix Assignment in DHCPv6 November 2011 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Address Auto-configuration . . . . . . . . . . . . . . . . . . 4 4. DHCPv6 Operation . . . . . . . . . . . . . . . . . . . . . . . 5 5. DHCPv6 IA_PA Option . . . . . . . . . . . . . . . . . . . . . 6 5.1. Identity Association for Prefix Assignment Option . . . . 6 5.2. IA_PA Prefix Option . . . . . . . . . . . . . . . . . . . 7 6. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 8 7. IANA consideration . . . . . . . . . . . . . . . . . . . . . . 8 8. Security Considerations . . . . . . . . . . . . . . . . . . . 8 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 10.1. Normative References . . . . . . . . . . . . . . . . . . . 9 10.2. Informative references . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 Jiang, et al. Expires May 24, 2012 [Page 2] Internet-Draft Prefix Assignment in DHCPv6 November 2011 1. Introduction [RFC3315] describes the operation of address assignment by a DHCPv6 server. A client uses a Solicit message to discover DHCPv6 servers configured to assign addresses. A server sends an Advertise message in response to announce the availability of the server to the client. The client then uses a Request message to request addresses. The server then returns addresses in a Reply message. The operation assumes that the server is responsible for the assignment of an integral address which includes prefix and interface identifier parts as described in [RFC4291]. This document introduces a new DHCPv6 procedure to configure hosts' IPv6 addresses. In this new procedure, the prefix is advertised from a DHCPv6 server through DHCPv6 protocol while the interface identifiers are independently generated by the hosts. [RFC3633] defines Prefix Delegation options providing a mechanism for automated delegation of IPv6 prefixes using the DHCPv6. This mechanism is intended for delegating a long-lived prefix from a delegating router to a requesting router. This mechanism "is not bound to the assignment of IP addresses or other configuration information to hosts" [RFC3633]. It delegates prefixes to a routable device for itself use only. It does not support the host-genarated interface identifiers model, in which prefix(es) need to be advertised or assigned to hosts. [RFC3972] describes a method for binding a public signature key to an IPv6 address in the Secure Neighbor Discovery (SEND) protocol [RFC3971]. The basic idea is to generate the interface identifier (i.e., the rightmost 64 bits) of the IPv6 address by computing a cryptographic hash of the public key. That is, the host decides its interface identifier. As for the prefix part of the CGA, it is probably got through Router Advertisement message defined in [RFC4861], or through DHCPv6 operations defined in this document. [I-D.ietf-csi-dhcpv6-cga-ps] describes potential issues in the interaction between DHCPv6 and CGA. In that document , the usage of DHCPv6 for assigning prefixes is proposed to facilitate separation of prefix assignment and interface identifier generation. There are also other host-generated IPv6 addresses, which are combined by prefixes obtained from network configuration and ingerface identifiers generated by hosts, such as modified EUI-64 interface identifier [EUI-64], temporary addresses for privacy [RFC4941],etc. The DHCPv6 operations defined in this document also supports such address methods. The DHCPv6 operations defined in this document also supports the Jiang, et al. Expires May 24, 2012 [Page 3] Internet-Draft Prefix Assignment in DHCPv6 November 2011 assigned prefix to be shared across multiple hosts. 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 [RFC2119]. The terminology in this document is based on the definitions in [RFC3315], in addition to the ones specified in this section derivative prefix: A prefix is derived from another prefix. For example, a /64 prefix is derived from a /48 prefix, that is, the /64 prefix has the same leftmost 48 bits with the /48 prefix. authorized prefix: A specific router is given a specific set of subnet prefixes to advertise; other routers have an authorization to advertise other subnet prefixes. In [RFC3971],Certification Path Advertisement message is used to convey authorized prefixes. 3. Address Auto-configuration Router Advertisements in [RFC4861] allow routers to inform hosts how to perform Address Auto-configuration. For example, routers can specify whether hosts should use DHCPv6 and/or stateless address configuration. In Router Advertisement message, M and O bits are used for indication of address auto-configuration mode. Whatever address auto-configuration mode a host uses, the following two parts are necessary for the host to formulate it's IPv6 address: o A prefix. In [RFC3971], Certification Path Solicitation and Certification Path Advertisement messages are designed for verifying routers being authorized to act as routers. Certification Path Advertisement message can also be used to verify that routers are authorized to advertise a certain set of subnet prefixes. In the stateless auto-configuration address mode, the prefixes in Router Advertisement message should be a subset of authorized prefixes, or derivative prefixes from authorized prefixes. In the stateful auto-configuration address mode, prefix assignment from a DHCPv6 server is not currently support. o An interface identifier. Modified EUI-64 interface identifier [EUI-64] is a widely-used host generated interface identifier. It generates interface identifier from the host MAC address. The interface identifier of [RFC3972] is generated by computing a cryptographic hash of a public key of a host. The host is Jiang, et al. Expires May 24, 2012 [Page 4] Internet-Draft Prefix Assignment in DHCPv6 November 2011 responsible for interface identifier generation. In the ND-managed environment, RA is used to assign the prefix. So far, there is no mechanism to support the scenario that prefixes are managed by a DHCPv6 server. The DHCPv6 operation defined in this document enables the DHCPv6 server to assign a prefix, rather than a integral address, to the host, so that the host can obtain an IPv6 address by combining the prefix with its own generated interface identifier. It actually enables the auto address configuration through DHCPv6. This document targets to meet this gap. 4. DHCPv6 Operation Figure 1 shows the operation of separating prefix assignment and interface identifier generation in the DHCPv6. +------------+ +-------------+ |Host(Client)| |DHCPv6 Server| +------------+ +-------------+ | 1 Solicit | |---------------------> | | 2 Advertise | |<--------------------- | 3 Combination of Prefix | and Interface Identifier | | | Figure 1: DHCPv6 Operation 1. A host uses a Solicit message to discover DHCPv6 servers that have been configured to assign prefixes for the host. Identity Association for Prefix Delegation Option (IA_PD) is defined in [RFC3633] for prefix delegation between a requesting router and delegating router. Referring to the definition, a new Identity Association for Prefix Assignment (IA-PA) option is defined in Section 5.1 to enable the prefix assignment from a DHCPv6 server to a host. 2. The DHCPv6 server assigns one or more prefixes to the host in Advertise messages or in the Reply messages to the prefix requests from the hosts. The assigned prefixes SHOULD be a subset of the authorized prefixes or derivative prefixes of the authorized prefixes. Identity Association for Prefix Assignment Option in Section 5.1 is used for conveying the assigned prefixes. If there is not a proper prefix available, a status- code is returned to the host and the procedure is terminated. Jiang, et al. Expires May 24, 2012 [Page 5] Internet-Draft Prefix Assignment in DHCPv6 November 2011 When receiving multiple prefixes, the host may use pre-configured hints for prefix assignment preference. The hints are authorized prefixes advertised by an authorized router through Certification Path Advertisement defined in [RFC3971]. 3. The host generates an interface identifier and formulates a combined IPv6 address by concatenating the assigned prefix and the self-generated interface identifier. There are many ways to generate interface identifier. [RFC3972] defines a method to generate the interface identifier by computing a cryptographic hash of a public key of the host. Modified EUI-64 interface identifier [EUI-64] is generated based on the host MAC address. After the host generates an IPv6 address using the above procedure, the host may send a Request message to the DHCPv6 server in order to confirm the usage of the new address. The confirmation procedure may be completed together with the address registration procedure. However, the confirmation procedure is out of scope. 5. DHCPv6 IA_PA Option In this section, one new option is defined, Identity Association for Prefix Assignment Option . The format of this new DHCPv6 IA_PA Option has been deliberately designed to be the same with IA_PD option[RFC3633]. The IA_PD Prefix and IA Address sub-options from IA_PD option are also reused. However, the two options are different on the semantics and usage models. The prefixed assigned through this DHCPv6 IA_PA option could be shared accross multiple hosts. 5.1. Identity Association for Prefix Assignment Option The IA_PA option is used to carry a prefix assignment identity association, the parameters associated with the IA_PA and the prefixes associated with it. The format of the IA_PA option is: Jiang, et al. Expires May 24, 2012 [Page 6] Internet-Draft Prefix Assignment in DHCPv6 November 2011 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPTION_IA_PA | option-length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IAID (4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | T1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | T2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . IA_PA-options . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code: OPTION_IA_PA (TBA1) option-length: 12 + length of IA_PA-options field. IAID: The unique identifier for this IA_PA; the IAID must be unique among the identifiers for all of this host's IA_PAs. T1: The time at which the host should contact the DHCPv6 server from which the prefixes in the IA_PA were obtained to extend the lifetimes of the prefixes assigned to the IA_PA; T1 is a time duration relative to the current time expressed in units of seconds. T2: The time at which the host should contact any available DHCPv6 server to extend the lifetimes of the prefixes assigned to the IA_PA; T2 is a time duration relative to the current time expressed in units of seconds. IA_PA-options: Options associated with this IA_PA. The details of the fields are similar to the IA_PD option description in [RFC3633]. The difference is here a DHCPv6 server and a host involved, while a delegating router and requesting router involved in [RFC3633]. 5.2. IA_PA Prefix Option OPTION_IAPREFIX (26) "IA_PD Prefix Option" defined in Section 10 of [RFC3633] is reused. Jiang, et al. Expires May 24, 2012 [Page 7] Internet-Draft Prefix Assignment in DHCPv6 November 2011 Originally, the option is used for conveying prefix information between a delegating router and a requesting router. Here the IA_PD Prefix option is used to specify IPv6 address prefixes associated with an IA_PA in Section 5.1. The IA_PD Prefix option must be encapsulated in the IA_PA-options field of an IA_PA option. 6. Applicability In point-to-point link model, DHCPv6 operation with host-generated interface identifier, described in this document, may be used. [RFC4968] provides different IPv6 link models that are suitable for 802.16 based networks and a point-to-point link model is recommended. Also, 3GPP and 3GPP2 have earlier adopted the point-to-point link model based on the recommendations in [RFC3314]. In this model, one prefix can only be assigned to one interface of a host (mobile station) and different hosts (mobile stations) can't share a prefix. The unique prefix can be used to identify the host. It is not necessary for a DHCPv6 server to generate an interface identifier for the host. The host may generate its interface identifier as described in [RFC4941]. An interface identifier could even be generated via random number generation. Modified EUI-64 interface identifier [EUI-64] is also typically generated by hosts. [RFC4941] has defined temporary addresses for privacy purposes. The temporary addresses is also generated by hosts using random algorithm. The DHCPv6 operations defined in this document also supports such address methods. 7. IANA consideration This document defines a new DHCPv6 [RFC3315] option, which must be assigned Option Type values within the option numbering space for DHCPv6 messages: The OPTION_IA_PA Option (TBA1), described in Section 5.1. 8. Security Considerations Security considerations in DHCPv6 are described in [RFC3315]. To guard against attacks through prefix assignment, a host and a DHCPv6 server SHOULD use DHCPv6 authentication as described in Section 21, "Authentication of DHCP messages" of [RFC3315] or Secure DHCPv6 [I-D.ietf-dhc-secure-dhcpv6] . Jiang, et al. Expires May 24, 2012 [Page 8] Internet-Draft Prefix Assignment in DHCPv6 November 2011 9. Acknowledgements The authors would like to thanks Suresh Krishnan, Ted Lemon and other members of DHC WG for their valuable comments. 10. References 10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, September 2007. [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005. [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", RFC 3972, March 2005. [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6", RFC 3633, December 2003. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006. [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy Extensions for Stateless Address Autoconfiguration in IPv6", RFC 4941, September 2007. 10.2. Informative references [RFC4968] Madanapalli, S., "Analysis of IPv6 Link Models for 802.16 Based Networks", RFC 4968, August 2007. [RFC3314] Wasserman, M., "Recommendations for IPv6 in Third Generation Partnership Project (3GPP) Standards", RFC 3314, September 2002. [I-D.ietf-csi-dhcpv6-cga-ps] Jiang, et al. Expires May 24, 2012 [Page 9] Internet-Draft Prefix Assignment in DHCPv6 November 2011 Jiang, S., Shen, S., and T. Chown, "DHCPv6 and CGA Interaction: Problem Statement", draft-ietf-csi-dhcpv6-cga-ps-07 (work in progress), May 2011. [I-D.ietf-dhc-secure-dhcpv6] Jiang, S. and S. Shen, "Secure DHCPv6 Using CGAs", draft-ietf-dhc-secure-dhcpv6-03 (work in progress), June 2011. [EUI-64] "Guidelines for 64-bit Global Identifier (EUI-64) Registration Authority", http://standards.ieee.org/ regauth/oui/tutorials/EUI64.html", March 1997. Authors' Addresses Sheng Jiang Huawei Technologies Q14, Huawei Campus, No.156, BeiQing Road Hai-Dian District, Beijing 100095 P.R. China Email: jiangsheng@huawei.com Frank Xia Huawei Technologies 1700 Alma Dr. Suite 500 Plano, TX 75075 Email: xiayangsong@huawei.com Behcet Sarikaya Huawei Technologies 1700 Alma Dr. Suite 500 Plano, TX 75075 Email: sarikaya@ieee.org Jiang, et al. Expires May 24, 2012 [Page 10]