IPv6 Group R. Droms Internet-Draft P. Thubert Expires: September 29, 2005 Cisco March 28, 2005 DHCPv6 Prefix Delegation for NEMO draft-droms-nemo-dhcpv6-pd-02.txt Status of this Memo This document is an Internet-Draft and is subject to all provisions of Section 3 of RFC 3667. By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she become aware will be disclosed, in accordance with RFC 3668. 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 September 29, 2005. Copyright Notice Copyright (C) The Internet Society (2005). 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. Droms & Thubert Expires September 29, 2005 [Page 1] Internet-Draft DHCPv6 Prefix Delegation for NEMO March 2005 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, whether from the Home Network or locally from an Access Network. 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 mobile host (MH) 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 in basic network mobility support [7] include the ability of the MR to receive delegated prefixes that can then be Droms & Thubert Expires September 29, 2005 [Page 2] Internet-Draft DHCPv6 Prefix Delegation for NEMO March 2005 assigned to links in the mobile network. DHCPv6PD can be used to meet this requirement for prefix delegation. 3.1 Delegating Home prefixes 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. 3.1.1 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 may be sent between the HA and the MR through the tunnel. 3.1.2 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 & Thubert Expires September 29, 2005 [Page 3] Internet-Draft DHCPv6 Prefix Delegation for NEMO March 2005 3.1.3 Location of DHCPv6PD Delegating Router function Support of DHCPv6PD in a mobile network is optional. If DHCPv6PD is used then 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. 3.1.4 Other DHCPv6 functions 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. The HA may act as a DHCPv6 relay agent for MHs while it acts as a DR for MRs. 3.2 Delegating Access Prefixes A Mobile Router may also obtain a temporary delegated prefix from its Access Router (acting as a DHCPv6PD DR) while the MR is roaming within the AR space. This is used for instance if the MR opens a network for anonymous visitors to roam in. In that model, the delegated network is advertised in the clear, as opposed to the MR's own Mobile Network Prefixes, which can stay private, over secured media. As a result, the CareOf Addresses of the visitors in a nested structure are all aggregated by a larger prefix owned, subdelegated, and advertised to the infrastructure by the Access Router itself. It is possible to protect the privacy of both parties between a VMN that implements RFC 3041 [9] and a visited MR that advertises only the delegated prefixes in the clear. In the case of a nested structure, it is expected that the AR and the MR maintain a tunnel and that the connectivity between the two is maintained somehow; this can be achieved by: o Performing a routing protocol such as a MANET within the nested topology. o performing some L3 bridging technique between AR and MRs. o placing a Nemo Home Agent at the AR so that the MR registers the mobility of the delegated prefix while it is roaming inside or outside the nested structure below the AR. Droms & Thubert Expires September 29, 2005 [Page 4] Internet-Draft DHCPv6 Prefix Delegation for NEMO March 2005 It may be beneficial for the Mobile Router to use its address within its delegated prefix as CareOf to register to its Home Agent. As a result, the MR gets some advantages similar to those obtained with HMIP. 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. 6. Normative References [1] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6", RFC 3633, December 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 3513, April 2003. [4] Johnson, D., Perkins, C. and J. Arkko, "Mobility Support in IPv6", RFC 3775, June 2004. [5] Ernst, T. and H. Lach, "Network Mobility Support Terminology", Internet-Draft draft-ietf-nemo-terminology-03, February 2005. [6] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. [7] Ernst, T., "Network Mobility Support Goals and Requirements", Droms & Thubert Expires September 29, 2005 [Page 5] Internet-Draft DHCPv6 Prefix Delegation for NEMO March 2005 Internet-Draft draft-ietf-nemo-requirements-04, February 2005. [8] Devarapalli, V., Wakikawa, R., Petrescu, A. and P. Thubert, "Network Mobility (NEMO) Basic Support Protocol", RFC 3963, January 2005. [9] Narten, T. and R. Draves, "Privacy Extensions for Stateless Address Autoconfiguration in IPv6", RFC 3041, January 2001. Authors' Addresses Ralph Droms Cisco 1414 Massachusetts Avenue Boxborough, MA 01719 USA Phone: +1 978.936.1674 Email: rdroms@cisco.com Pascal Thubert Cisco Village d'Entreprises Green Side 400, Avenue Roumanille Biot - Sophia Antipolis 06410 FRANCE Email: pthubert@cisco.com Appendix A. Changes Log Rev -01: The section on access prefix delegation was added. That section provides a mechanism that is very close to HMIP but purely based on standard DHCP-PD. It is limited to Nemo applications, but it provides additional features, including the privacy of the mobile access router. Rev -02: The section on optimization of access prefix delegation was removed. Droms & Thubert Expires September 29, 2005 [Page 6] Internet-Draft DHCPv6 Prefix Delegation for NEMO March 2005 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. 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Copyright Statement Copyright (C) The Internet Society (2005). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Droms & Thubert Expires September 29, 2005 [Page 7] Internet-Draft DHCPv6 Prefix Delegation for NEMO March 2005 Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Droms & Thubert Expires September 29, 2005 [Page 8]