A Method for Generating Link-Scoped IPv6 Multicast Addresses
RFC 4489

Network Working Group                                          J-S. Park
Request for Comments: 4489                                     M-K. Shin
Updates: 3306                                                   H-J. Kim
Category: Standards Track                                           ETRI
                                                              April 2006

      A Method for Generating Link-Scoped IPv6 Multicast Addresses

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 Internet Society (2006).

Abstract

   This document specifies an extension to the multicast addressing
   architecture of the IPv6 protocol.  The extension allows the use of
   Interface Identifiers (IIDs) to allocate multicast addresses.  When a
   link-local unicast address is configured at each interface of a node,
   an IID is uniquely determined.  After that, each node can generate
   its unique multicast addresses automatically without conflicts.  The
   alternative method for creating link-local multicast addresses
   proposed in this document is better than known methods like unicast-
   prefix-based IPv6 multicast addresses.  This memo updates RFC 3306.

Table of Contents:

   1. Introduction ....................................................2
   2. Applicability ...................................................2
   3. Link-Scoped Multicast Address Format ............................3
   4. Example .........................................................3
   5. Consideration of Lifetime .......................................4
   6. Security Considerations .........................................4
   7. Acknowledgements ................................................4
   8. References ......................................................5

Park, et al.                Standards Track                     [Page 1]
RFC 4489               Link-Scoped IPv6 Multicast             April 2006

1.  Introduction

   This document defines an extension to the multicast portion of the
   IPv6 addressing architecture [RFC4291].  The current architecture
   does not contain any built-in support for dynamic address allocation.
   The extension allows for use of IIDs to allocate multicast addresses.
   When a link-local unicast address is configured at each interface of
   a node, an IID is uniquely determined.  After that, each node can
   generate its unique multicast addresses automatically without
   conflicts.  That is, these addresses could safely be configured at
   any time after Duplicate Address Detection (DAD) has completed.

   This method for the link-local scope is preferred over unicast-
   prefix-based IPv6 multicast addresses [RFC3306], since by delegating
   multicast addresses using the IID, each node can generate its
   multicast addresses automatically without allocation servers.  This
   method works better than the unicast-prefix-based method with
   applications in serverless environments such as ad-hoc and network
   mobility.  This document restricts the usage of defined fields such
   as the scop, plen, and network prefix fields of [RFC3306].
   Therefore, this document specifies encoded information for link-local
   scope in multicast addresses.

   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 [RFC2119].

2.  Applicability

   The allocation technique in this document is designed to be used in
   any environment in which link-local scope IPv6 multicast addresses
   are assigned or selected.  This method goes especially well with
   nodes supplying multicast services in a zeroconf/serverless
   environment.  For example, multicast addresses less than or equal to
   link-local scope are themselves generated by nodes supplying
   multicast services without conflicts.  Also, hosts that are supplied
   multicast services from multicast servers then make multicast
   addresses of multicast servers using ND (address resolution) and
   well-known group IDs [RFC2461].

   Consequently, this technique MUST only be used for link scoped
   multicast addresses.  If you want to use multicast addresses greater
   than link-local scope, you need to use other methods as described in
   [RFC3306].

Park, et al.                Standards Track                     [Page 2]