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Versions: 00 01 02 RFC 3587

INTERNET-DRAFT                                         R. Hinden, Nokia
February 4, 2003                                      S. Deering, Cisco



       IPv6 Global Unicast Address Format for the 2000::/3 Prefix

                <draft-ietf-ipv6-unicast-aggr-v2-01.txt>



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 August 4, 2003.


Abstract

   This document defines the unicast address format for the 2000::/3
   (001 binary) prefix.  The address format defined in this document is
   consistent with RFC2460 "Internet Protocol, Version 6 (IPv6)
   Specification" and RFCXXXX "IP Version 6 Addressing Architecture".

   This documented replaces RFC2374 "An IPv6 Aggregatable Global Unicast
   Address Format".  RFC2374 will become historic.







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1.0 Introduction

   This document defines the unicast address format for the 2000::/3
   (001 binary) prefix.  The address format defined in this document is
   consistent with the IPv6 Protocol [IPV6] and the "IPv6 Addressing
   Architecture" [ARCH].  It is designed to facilitate scalable Internet
   routing.

   RFC2374, "An IPv6 Aggregatable Global Unicast Address Format" defined
   a structured allocation structure of global unicast IPv6 addresses
   with named fields (e.g., TLA, NLA, etc.).

   While this approach was originally thought to be a good way to
   allocate IPv6 addresses, subsequent experience and discussion showed
   that it would be better to leave flexibility in the definition of
   IPv6 allocation policies to the Internet Address Registries, in order
   to allow a better balance among the competing requirements.  This is
   consistent with the recommendations made by the IAB and IESG in
   [RFC3177].

   This document removes the defined structure and generalizes the
   fields in the global unicast address format.

   This documented replaces RFC2374, "An IPv6 Aggregatable Global
   Unicast Address Format".  RFC 2374 will become historic.

   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 [RFC 2119].


2.0 Address Format

   The general format for IPv6 global unicast addresses as defined in
   "IP Version 6 Addressing Architecture" [ARCH] is as follows:

      |         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].

   [ARCH] also requires that all unicast addresses, except those that
   start with binary value 000, have Interface IDs that are 64 bits long



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   and to be constructed in Modified EUI-64 format.

   The specific format of global unicast address under the 2000::/3
   prefix is:

      | 3 |     n bits         | 61-n bits |       64 bits              |
      +---+--------------------+-----------+----------------------------+
      |001|  routing prefix    | subnet ID |       interface ID         |
      +---+--------------------+-----------+----------------------------+

   where the routing prefix is a value assigned to a 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].


3.0 Acknowledgments

   The authors would like to express our thanks to Margaret Wasserman,
   Brian Carpenter, Pekka Savola, Alain Durand, Fred Templin, Michel Py,
   and Jun-ichiro itojun Hagino for their review and constructive
   comments.


4.0 References

   Normative

   [ARCH]    Hinden, R., "IP Version 6 Addressing Architecture",
             Internet Draft, <draft-ietf-ipngwg-addr-arch-v3-11.txt>,
             October 2002.

   [IPV6]    Deering, S., R. Hinden, "Internet Protocol, Version 6
             (IPv6) Specification", RFC2460, December 1998.

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", RFC2119, BCP14, March 1997.

   [RFC3177] IAB/IESG, "Recommendations on IPv6 Address Allocations to
             Sites" RFC3177, September 2001.


5.0 Security Considerations

   IPv6 addressing documents do not have any direct impact on Internet
   infrastructure security.





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6.0 Authors' Addresses

   Robert M. Hinden
   Nokia
   313 Fairchild Drive
   Mountain View, CA
   US

   email: hinden@iprg.nokia.com

   Stephen E. Deering
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA 95134-1706
   US

   email: deering@cisco.com


































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