RFC 3306 (rfc3306) - Page 2 of 7

Unicast-Prefix-based IPv6 Multicast Addresses

RFC 3306          Unicast-Prefix-based IPv6 Multicast        August 2002


1. Introduction

   This document specifies an extension to the multicast portion of the
   IPv6 addressing architecture [ADDRARCH].  The current architecture
   does not contain any built-in support for dynamic address allocation.
   This proposal introduces encoded information in the multicast address
   to allow for dynamic allocation of IPv6 multicast addresses and IPv6
   source-specific multicast addresses.

2. Motivation

   The current IPv4 multicast address allocation architecture [RFC 2908]
   is based on a multi-layered, multi-protocol system.  The goal of this
   proposal is to reduce the number of protocols that need to be
   deployed in order to get dynamic multicast address allocation.

   The use of unicast prefix-based multicast address allocation will, at
   a minimum, remove the need to run the Multicast Address Allocation
   Protocol (AAP) [AAP WORK] and the Multicast Address-Set Claim (MASC)
   Protocol [RFC 2909].

3. 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].

4. Multicast Address Format

   Section 2.7 of [ADDRARCH] defines the following operational format of
   IPv6 multicast addresses:

      |    8   |  4 |  4 |                     112                     |
      +--------+----+----+---------------------------------------------+
      |11111111|flgs|scop|                  group ID                   |
      +--------+----+----+---------------------------------------------+















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