INTERNET-DRAFT R. Hinden, Nokia June 19, 2003 S. Deering, Cisco E. Nordmark, Sun IPv6 Global Unicast Address Format Status of this Memo This document is an Internet-Draft and is subject to 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/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This internet draft expires on December 24, 2003. Abstract RFC2374 "An IPv6 Aggregatable Global Unicast Address Format" defined an IPv6 address allocation structure that includes TLA (Top Level Aggregator) and NLA (Next Level Aggregator). This document replaces RFC2374, and makes RFC 2374 and the TLA/NLA structure historic. draft-ietf-ipv6-unicast-aggr-v2-03.txt [Page 1] INTERNET-DRAFT IPv6 Global Unicast Address Format June 2003 1.0 Introduction RFC2374 "An IPv6 Aggregatable Global Unicast Address Format" defined an IPv6 address allocation structure that includes TLA (Top Level Aggregator) and NLA (Next Level Aggregator). This document replaces RFC2374, and makes RFC 2374 and the TLA/NLA structure historic. 2.0 TLA/NLA Made Historic The TLA/NLA scheme has been replaced by a coordinated allocation policy defined by the Regional Internet Registries (RIRs) [IPV6RIR]. Part of the motivation for obsoleting the TLA/NLA structure is technical; for instance, there is concern that TLA/NLA is not the technically best approach at this stage of the deployment of IPv6. Moreover, the allocation of IPv6 addresses is related to policy and to the stewardship of the IP address space and routing table size, which the RIRs have been managing for IPv4. It is likely that the RIRs' policy will evolve as IPv6 deployment proceeds. The IETF has provided technical input to the RIRs (for example, [RFC3177]), which the RIRs have taken into account when defining their address allocation policy. RFC2374 was the definition of addresses for Format Prefix 001 (2000::/3) which is formally made historic by this document. Even though currently only 2000::/3 is being delegated by the IANA, implementations should not make any assumptions about 2000::/3 being special, since the IANA might later be directed to delegate currently unassigned parts of the IPv6 address space to the purpose of Global Unicast as well. The SLA (subnet local aggregator) field in RFC2374 remains in function but with a different name in [ARCH]. Its new name is "subnet ID". This documented replaces RFC2374, "An IPv6 Aggregatable Global Unicast Address Format". RFC2374 will become historic. 3.0 Address Format The general format for IPv6 global unicast addresses as defined in "IP Version 6 Addressing Architecture" [ARCH] is as follows: draft-ietf-ipv6-unicast-aggr-v2-03.txt [Page 2] INTERNET-DRAFT IPv6 Global Unicast Address Format June 2003 | n bits | m bits | 128-n-m bits | +-------------------------+-----------+----------------------------+ | global routing prefix | subnet ID | interface ID | +-------------------------+-----------+----------------------------+ where the global routing prefix is a (typically hierarchically- structured) value assigned to a site (a cluster of subnets/links), the subnet ID is an identifier of a subnet within the site, and the interface ID is as defined in section 2.5.1 of [ARCH]. The global routing prefix is designed to be hierarchically structured by the RIRs and ISPs, and the subnet field is designed to be hierarchically structured by site administrators. [ARCH] also requires that all unicast addresses, except those that start with binary value 000, have Interface IDs that are 64 bits long and to be constructed in Modified EUI-64 format. The format of global unicast address in this case is: | n bits | 64-n bits | 64 bits | +-------------------------+-----------+----------------------------+ | global routing prefix | subnet ID | interface ID | +-------------------------+-----------+----------------------------+ where the routing prefix is a value assigned to identify a site (a cluster of subnets/links), the subnet ID is an identifier of a subnet within the site, and the interface ID is in modified EUI-64 format as defined in [ARCH]. An example of the resulting format of global unicast address under the 2000::/3 prefix that is currently being delegated by the IANA and consistent with the recommendations in RFC3177 is: | 3 | 45 bits | 16 bits | 64 bits | +---+---------------------+-----------+----------------------------+ |001|global routing prefix| subnet ID | interface ID | +---+---------------------+-----------+----------------------------+ draft-ietf-ipv6-unicast-aggr-v2-03.txt [Page 3] INTERNET-DRAFT IPv6 Global Unicast Address Format June 2003 4.0 Acknowledgments The authors would like to express our thanks to Alain Durand, Brian Carpenter, Fred Templin, Julian Sellers, Jun-ichiro itojun Hagino, Margaret Wasserman, Michel Py, Pekka Savola, Tatuya Jinmei, and Thomas Narten for their review and constructive comments. 5.0 References Normative [ARCH] Hinden, R., S. Deering, "IP Version 6 Addressing Architecture", RFC3513, April 2003. [IPV6] Deering, S., R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC2460, December 1998. Non-Normative [IPV6RIR] APNIC, ARIN, RIPE NCC, "IPv6 Address Allocation and Assignment Policy", Document ID: ripe-267, http://www.ripe.net/ripe/docs/ipv6policy.html, January 22, 2003. [RFC3177] IAB/IESG, "Recommendations on IPv6 Address Allocations to Sites" RFC3177, September 2001. 6.0 Security Considerations IPv6 addressing documents do not have any direct impact on Internet infrastructure security. 7.0 Authors' Addresses Robert M. Hinden email: bob.hinden@nokia.com Nokia 313 Fairchild Drive Mountain View, CA US Stephen E. Deering email: deering@cisco.com Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134-1706 US draft-ietf-ipv6-unicast-aggr-v2-03.txt [Page 4] INTERNET-DRAFT IPv6 Global Unicast Address Format June 2003 Erik Nordmark email: erik.nordmark@sun.com Sun Microsystems Laboratories 180, avenue de l'Europe 38334 SAINT ISMIER Cedex France draft-ietf-ipv6-unicast-aggr-v2-03.txt [Page 5]