Network Working Group                                        S. Miyakawa
Request for Comments: 3769                NTT Communications Corporation
Category: Informational                                         R. Droms
                                                                   Cisco
                                                               June 2004

                Requirements for IPv6 Prefix Delegation

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2004).

Abstract

   This document describes requirements for how IPv6 address prefixes
   should be delegated to an IPv6 subscriber's network (or "site").

1.  Introduction

   With the deployment of IPv6 [1], several Internet Service Providers
   are ready to offer IPv6 access to the public.  In conjunction with
   widely deployed "always on" media such as ADSL and the expectation
   that customers will be assigned a /48 IPv6 unicast address prefix
   (see RFC 3513 [3] and section 3 of RFC 3177 [2]), an efficient
   mechanism for delegating address prefixes to the customer's sites is
   needed.  The delegation mechanism will be intended to automate the
   process of informing the customer's networking equipment of the
   prefixes to be used at the customer's site.

   This document clarifies the requirements for IPv6 address prefix
   delegation from the ISP to the site.

2.  Scenario and terminology

   The following figure illustrates a likely example for the
   organization of a network providing subscription IPv6 service:

                                                     /------\
                                                    /        \
                                                   +          |
                                                  / \        /
        +---------------+              +--------+/   \------/
        |ISP Edge Router|Point-to-point|Customer+
        |               +--------------+ Router |  Customer networks
        |     (PE)      |     link     | (CPE)  +
        +---------------+              +--------+\   /------\
                                                  \ /        \
                                                   +          |
                                                    \        /
                                                     \------/

   Figure 1: Illustration of ISP-customer network architecture

   Terminology:

   PE:   Provider edge device; the device connected to the service
         provider's network infrastructure at which the link to the
         customer site is terminated

   CPE:  Customer premises equipment; the device at the customer site at
         which the link to the ISP is terminated

3.  Requirements for Prefix Delegation

   The purpose of the prefix delegation mechanism is to delegate and
   manage prefixes to the CPE automatically.

3.1.  Number and Length of Delegated Prefixes

   The prefix delegation mechanism should allow for delegation of
   prefixes of lengths between /48 and /64, inclusively.  Other lengths
   should also be supported.  The mechanism should allow for delegation
   of more than one prefix to the customer.

3.2.  Use of Delegated Prefixes in Customer Network

   The prefix delegation mechanism must not prohibit or inhibit the
   assignment of longer prefixes, created from the delegated prefixes,
   to links within the customer network.  The prefix delegation
   mechanism is not required to report any prefix delegations within the
   customer's network back to the ISP.

3.3.  Static and Dynamic Assignment

   The prefix delegation mechanism should allow for long-lived static
   pre-assignment of prefixes and for automated, possibly short-lived,
   on-demand, dynamic assignment of prefixes to a customer.

3.4.  Policy-based Assignment

   The prefix delegation mechanism should allow for the use of policy in
   assigning prefixes to a customer.  For example, the customer's
   identity and type of subscribed service may be used to determine the
   address block from which the customer's prefix is selected, and the
   length of the prefix assigned to the customer.

3.5.  Expression of Requirements or Preferences by the CPE

   The CPE must be able to express requirements or preferences in its
   request to the PE.  For example, the CPE should be able to express a
   preference for a prefix length.

3.6.  Security and Authentication

   The prefix delegation mechanism must provide for reliable
   authentication of the identity of the customer to which the prefixes
   are to be assigned, and must provide for reliable, secure
   transmission of the delegated prefixes to the customer.

   The prefix delegation should provide for reliable authentication of
   the identity of the service provider's edge router.

3.7.  Accounting

   The prefix delegation mechanism must allow for the ISP to obtain
   accounting information about delegated prefixes from the PE.

3.8.  Hardware technology Considerations

   The prefix delegation mechanism should work on any hardware link
   technology between the PE and the CPE and should be hardware
   technology independent.  The mechanism must work on shared links.

   The mechanism should work with all hardware technologies with either
   an authentication mechanism or without, but ISPs would like to take
   advantage of the hardware technology's authentication mechanism if it
   exists.

4.  Security considerations

   Section 3.6 specifies security requirements for the prefix delegation
   mechanism.  For point to point links, where one trusts that there is
   no man in the middle, or one trusts layer two authentication,
   authentication may not be necessary.

   A rogue PE can issue bogus prefixes to a requesting router.  This may
   cause denial of service due to unreachability.

   A rogue CPE may be able to mount a denial of service attack by
   repeated requests for delegated prefixes that exhaust the PE's
   available prefixes.

5.  Acknowledgments

   The authors would like to express thanks to Randy Bush, Thomas
   Narten, Micheal Py, Pekka Savola, Dave Thaler, as well as other
   members of the IPv6 working group and the IESG for their review and
   constructive comments.  The authors would also like to thank the
   people in the IPv6 operation group of the Internet Association of
   Japan and NTT Communications IPv6 project, especially Toshi Yamasaki
   and Yasuhiro Shirasaki for their original discussion and suggestions.

6.  Informative References

   [1]  Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
        Specification", RFC 2460, December 1998.

   [2]  IAB and IESG, "IAB/IESG Recommendations on IPv6 Address", RFC
        3177, September 2001.

   [3]  Hinden, R. and S. Deering, "Internet Protocol Version 6 (IPv6)
        Addressing Architecture", RFC 3513, April 2003.

7.  Authors' Addresses

   Shin Miyakawa
   NTT Communications Corporation
   Tokyo
   Japan

   Phone: +81-3-6800-3262
   EMail: miyakawa@nttv6.jp

   Ralph Droms
   Cisco
   1414 Massachusetts Avenue
   Boxborough, MA  01719
   USA

   Phone: +1 978.936.1674
   EMail: rdroms@cisco.com

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