Network Working Group R. Droms Internet-Draft Cisco Expires: December 22, 2003 June 23, 2003 DHCPv6 Prefix Delegation for NEMO draft-droms-nemo-dhcpv6-pd-00.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on December 22, 2003. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract One aspect of network mobility support is the assignment of a prefix or prefixes to a mobile router (MR) for use on the links in the mobile network. DHCPv6 prefix delegation can be used for this configuration task. 1. Introduction One aspect of network mobility support is the assignment of a prefix or prefixes to a mobile router for use on the links in the mobile network. DHCPv6 prefix delegation [1] (DHCPv6PD) can be used for this configuration task. Droms Expires December 22, 2003 [Page 1] Internet-Draft DHCPv6 Prefix Delegation for NEMO June 2003 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 [2]. The following terms used in this document are defined in the IPv6 Addressing Architecture document [3]: link-local unicast address link-local scope multicast address The following terms used in this document are defined in the mobile IPv6 specification [4]: home agent (HA) home link The following terms used in this document are defined in the mobile network terminology document [5]: mobile router (MR) mobile network The following terms used in this document are defined in the DHCPv6 [6] and DHCPv6 prefix delegation [1] specifications: delegating router (DR) requesting router (RR) DHCPv6 relay agent 3. Application of DHCPv6 prefix delegation to mobile networks The network mobility requirements document [7] defines a solution for mobile IPv6 networks based on the mobile IPv6 protocol [4]. In this solution, a MR uses the mobile IPv6 protocol to establish a maintain a session with its HA, and uses bidirectional tunneling between the MR and HA to provide a path through which hosts attached to links in the mobile network can maintain connectivity with nodes not in the mobile network. The requirements for basic network mobility support [8] include the Droms Expires December 22, 2003 [Page 2] Internet-Draft DHCPv6 Prefix Delegation for NEMO June 2003 ability of the MR to receive delegated prefixes that can then be assigned to links in the mobile network. DHCPv6PD can be used to meet this requirement for prefix delegation. To use DHCPv6PD for mobile networks, the HA assumes the role of the DR and the MR assumes the role of the RR. Throughout the remainder of this document, the HA will be assumed to be acting as a DHCPv6PD DR and the MR will be assumed to be acting as a RR. The HA and MR exchange DHCPv6PD protocol messages through the tunnel connecting them. The tunnel acts as the link labeled "DSL to subscriber premises" in figure 1 of the DHCPv6PD specification. The HA (acting as the DR) is provisioned with prefixes to be assigned using any of the prefix assignment mechanisms described in the DHCPv6PD specifications. Other updates to the HA data structures required as a side effect of prefix delegation are specified by the particular network mobility protocol. For example, in the case of "Basic Network Mobility Support" [8], the HA would add an entry in its binding cache registering the delegated prefix to the MR to which the prefix was delegated. 3.1 Use of HA-MR tunnel for DHCPv6 messages The DHCPv6 specification requires the use of link-local unicast and link-local scope multicast addresses in DHCPv6 messages (except in certain cases as defined in section 22.12 of the DHCPv6 specification). Section 10.4.2 of the mobile IPv6 specification describes forwarding of intercepted packets, and the third paragraph of that section begins: However, packets addressed to the mobile node's link-local address MUST NOT be tunneled to the mobile node. The DHCPv6 messages exchanged between the HA and the MR originate only with the HA and the MR, and therefore are not "intercepted packets" and are may be forwarded between the HA and the MR through the tunnel. 3.2 Exchanging DHCPv6 messages when HA and MR are on the same link When the MR is on its home link, the HA uses the home link to exchange DHCPv6PD messages with the MR, even if there is a tunnel across the home link between the MR and the HA. It is the responsibility of the implementation to determine when the MR is on its home link and to avoid use of any existing tunnel. Droms Expires December 22, 2003 [Page 3] Internet-Draft DHCPv6 Prefix Delegation for NEMO June 2003 3.3 Location of DHCPv6PD Delegating Router function The DHCPv6PD DR function MUST be implemented in the HA for the MR. The use of a DHCPv6 relay agent is not defined for DHCPv6PD. 3.4 Use of DHCPv6 for other configuration information The DHCPv6 messages exchanged between the MR and the HA may also be used for other DHCPv6 functions in addition to DHCPv6PD. For example, the HA may assign global addresses to the MR and may pass other configuration information such as a list of available DNS recursive resolvers to the MR using the same DHCPv6 messages as used for DHCPV6PD. 4. Security Considerations This document describes the use of DHCPv6 for prefix delegation in mobile networks. It does not introduce any additional security considerations beyond those described in the "Security Considerations" section of the DHCPv6 base specification [6] and the "Security Considerations" of the DHCPv6 Prefix Delegation specification [1]. Following the DHCPv6 Prefix Delegation specification, HAs and MRs SHOULD use DHCPv6 authentication as described in section "Authentication of DHCP messages" of the DHCPv6 specification [6], to guard against attacks mounted through prefix delegation. 5. IANA Considerations This document describes the use of DHCPv6 for prefix delegation in mobile networks. It does not introduce any additional IANA considerations. Normative References [1] Troan, O. and R. Droms, "IPv6 Prefix Options for DHCPv6", draft- ietf-dhc-dhcpv6-opt-prefix-delegation-04 (work in progress), June 2003. [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [3] Hinden, R. and S. Deering, "Internet Protocol Version 6 (IPv6) Addressing Architecture", RFC 2460, December 1998. [4] Johnson, D., Perkins, C. and J. Arkko, "Mobility Support in IPv6", draft-ietf-mobileip-ipv6-23 (work in progress), May 2003. Droms Expires December 22, 2003 [Page 4] Internet-Draft DHCPv6 Prefix Delegation for NEMO June 2003 [5] Ernst, T., "Network Mobility Support Terminology", draft-ietf- nemo-terminology-00 (work in progress), May 2003. [6] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", draft-ietf-dhc-dhcpv6-28 (work in progress), November 2002. [7] Ernst, T., "Network Mobility Support Goals and Requirements", draft-ietf-nemo-requirements-01 (work in progress), May 2003. [8] Wakikawa, R., Mitsuya, K., Uehara, K. and T. Ernst, "Basic Network Mobility Support", draft-wakikawa-nemo-basic-00 (work in progress), February 2003. Author's Address Ralph Droms Cisco 1414 Massachusetts Avenue Boxborough, MA 01719 Japan Phone: +1 978.936.1674 EMail: rdroms@cisco.com Droms Expires December 22, 2003 [Page 5] Internet-Draft DHCPv6 Prefix Delegation for NEMO June 2003 Full Copyright Statement Copyright (C) The Internet Society (2003). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. 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Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Droms Expires December 22, 2003 [Page 6]