Using Internet Group Management Protocol Version 3 (IGMPv3) and Multicast Listener Discovery Protocol Version 2 (MLDv2) for Source-Specific Multicast
RFC 4604

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Network Working Group                                        H. Holbrook
Request for Comments: 4604                                 Arastra, Inc.
Updates: 3376, 3810                                              B. Cain
Category: Standards Track                                Acopia Networks
                                                             B. Haberman
                                                                 JHU APL
                                                             August 2006

      Using Internet Group Management Protocol Version 3 (IGMPv3)
      and Multicast Listener Discovery Protocol Version 2 (MLDv2)
                     for Source-Specific Multicast

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

   The Internet Group Management Protocol Version 3 (IGMPv3) and the
   Multicast Listener Discovery Protocol Version 2 (MLDv2) are protocols
   that allow a host to inform its neighboring routers of its desire to
   receive IPv4 and IPv6 multicast transmissions, respectively.
   Source-specific multicast (SSM) is a form of multicast in which a
   receiver is required to specify both the network-layer address of the
   source and the multicast destination address in order to receive the
   multicast transmission.  This document defines the notion of an
   "SSM-aware" router and host, and clarifies and (in some cases)
   modifies the behavior of IGMPv3 and MLDv2 on SSM-aware routers and
   hosts to accommodate source-specific multicast.  This document
   updates the IGMPv3 and MLDv2 specifications.

Holbrook, et al.            Standards Track                     [Page 1]
RFC 4604                IGMPv3/MLDv2 for SSM                 August 2006

1.  Introduction

   The Internet Group Management Protocol (IGMP) [RFC1112, IGMPv2,
   IGMPv3] allows an IPv4 host to communicate IP multicast group
   membership information to its neighboring routers.  IGMP version 3
   (IGMPv3) [IGMPv3] provides the ability for a host to selectively
   request or filter traffic from individual sources within a multicast
   group.

   The Multicast Listener Discovery Protocol (MLD) [RFC2710, MLDv2]
   offers similar functionality for IPv6 hosts.  MLD version 2 (MLDv2)
   provides the analogous "source filtering" functionality of IGMPv3 for
   IPv6.

   Due to the commonality of function, the term "Group Management
   Protocol", or "GMP", will be used to refer to both IGMP and MLD.  The
   term "Source Filtering GMP", or "SFGMP", will be used to refer
   jointly to the IGMPv3 and MLDv2 group management protocols.

   The use of source-specific multicast is facilitated by small changes
   to the SFGMP protocols on both hosts and routers.  [SSM] defines
   general requirements that must be followed by systems that implement
   the SSM service model; this document defines the concrete application
   of those requirements to systems that implement IGMPv3 and MLDv2.  In
   doing so, this document defines modifications to the host and router
   portions of IGMPv3 and MLDv2 for use with SSM, and presents a number
   of clarifications to their behavior when used with SSM addresses.
   This document updates the IGMPv3 and MLDv2 specifications.

1.1.  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 [RFC2119].

   In order to emphasize the parts of this document that modify the
   existing protocol specifications ([RFC2710, MLDv2, IGMPv3]), as
   opposed to merely clarify them, any protocol modifications are marked
   with the tag "MODIFICATION".

2.  Host Requirements for Source-Specific Multicast

   This section defines the notion of an "SSM-aware" host and then goes
   on to describe the API requirements and the SFGMP protocol
   requirements of an SSM-aware host.  It is important to note that SSM
   can be used by any host that supports source filtering APIs and whose
   operating system supports the appropriate SFGMP.  The SFGMP

Holbrook, et al.            Standards Track                     [Page 2]
RFC 4604                IGMPv3/MLDv2 for SSM                 August 2006

   modifications described in this section make SSM work better on an
   SSM-aware host, but they are not strict prerequisites for the use of
   SSM.

   The 232/8 IPv4 address range is currently allocated for SSM by IANA
   [IANA-ALLOCATION].  In IPv6, the FF3x::/32 range (where 'x' is a
   valid IPv6 multicast scope value) is reserved for SSM semantics
   [RFC3306], although today SSM allocations are restricted to