RADIUS Delegated-IPv6-Prefix Attribute
RFC 4818

Network Working Group                                         J. Salowey
Request for Comments: 4818                                      R. Droms
Category: Standards Track                            Cisco Systems, Inc.
                                                              April 2007

                 RADIUS Delegated-IPv6-Prefix Attribute

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document defines a RADIUS (Remote Authentication Dial In User
   Service) attribute that carries an IPv6 prefix that is to be
   delegated to the user.  This attribute is usable within either RADIUS
   or Diameter.

Salowey & Droms             Standards Track                     [Page 1]
RFC 4818            Delegated-IPv6-Prefix Attribute           April 2007

1.  Introduction

   This document defines the Delegated-IPv6-Prefix attribute as a RADIUS
   [1] attribute that carries an IPv6 prefix to be delegated to the
   user, for use in the user's network.  For example, the prefix in a
   Delegated-IPv6-Prefix attribute can be delegated to another node
   through DHCP Prefix Delegation [2].

   The Delegated-IPv6-Prefix attribute can be used in DHCP Prefix
   Delegation between the delegating router and a RADIUS server, as
   illustrated in the following message sequence.

   Requesting Router   Delegating Router                   RADIUS Server
         |                     |                                 |
         |-Solicit------------>|                                 |
         |                     |-Request------------------------>|
         |                     |<--Accept(Delegated-IPv6-Prefix)-|
         |<--Advertise(Prefix)-|                                 |
         |-Request(Prefix)---->|                                 |
         |<--Reply(Prefix)-----|                                 |
         |                     |                                 |
                DHCP PD                      RADIUS

   The Framed-IPv6-Prefix attribute [4] is not designed to support
   delegation of IPv6 prefixes to be used in the user's network, and
   therefore Framed-IPv6-Prefix and Delegated-IPv6-Prefix attributes may
   be included in the same RADIUS packet.

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 RFC 2119 [3].

Salowey & Droms             Standards Track                     [Page 2]
RFC 4818            Delegated-IPv6-Prefix Attribute           April 2007

3.  Attribute Format

   The format of the Delegated-IPv6-Prefix is:

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |    Length     |  Reserved     | Prefix-Length |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   Prefix
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   Prefix
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   Prefix
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   Prefix                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type

           123 for Delegated-IPv6-Prefix

      Length

           The length of the entire attribute, in bytes.  At least 4 (to
           hold Type/Length/Reserved/Prefix-Length for a 0-bit prefix),
           and no larger than 20 (to hold Type/Length/ Reserved/Prefix-
           Length for a 128-bit prefix)

      Reserved

           Always set to zero by sender; ignored by receiver

      Prefix-Length

           The length of the prefix being delegated, in bits.  At least
           0 and no larger than 128 bits (identifying a single IPv6
           address)

   Note that the prefix field is only required to be long enough to hold
   the prefix bits and can be shorter than 16 bytes.  Any bits in the