Multicast Listener Discovery Version 2 (MLDv2) for IPv6
RFC 3810

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Network Working Group                                       R. Vida, Ed.
Request for Comments: 3810                                 L. Costa, Ed.
Updates: 2710                                                       LIP6
Category: Standards Track                                      June 2004

        Multicast Listener Discovery Version 2 (MLDv2) for IPv6

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 (2004).

Abstract

   This document updates RFC 2710, and it specifies Version 2 of the
   Multicast Listener Discovery Protocol (MLDv2).  MLD is used by an
   IPv6 router to discover the presence of multicast listeners on
   directly attached links, and to discover which multicast addresses
   are of interest to those neighboring nodes.  MLDv2 is designed to be
   interoperable with MLDv1.  MLDv2 adds the ability for a node to
   report interest in listening to packets with a particular multicast
   address only from specific source addresses or from all sources
   except for specific source addresses.

Vida & Costa                Standards Track                     [Page 1]
RFC 3810                     MLDv2 for IPv6                    June 2004

Table of Contents

   1.  Introduction. . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Protocol Overview . . . . . . . . . . . . . . . . . . . . . .   3
   3.  The Service Interface for Requesting IP Multicast Reception .   9
   4.  Multicast Listening State Maintained by Nodes . . . . . . . .  11
   5.  Message Formats . . . . . . . . . . . . . . . . . . . . . . .  13
   6.  Protocol Description for Multicast Address Listeners. . . . .  27
   7.  Protocol Description for Multicast Routers. . . . . . . . . .  34
   8.  Interoperation with MLDv1 . . . . . . . . . . . . . . . . . .  48
   9.  List of Timers, Counters, and their Default Values. . . . . .  51
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  55
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  56
   12. References. . . . . . . . . . . . . . . . . . . . . . . . . .  56
   13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  57
   Appendix A. Design Rationale. . . . . . . . . . . . . . . . . . .  58
   Appendix B. Summary of Changes from MLDv1 . . . . . . . . . . . .  59
   Editors' Contact Information. . . . . . . . . . . . . . . . . . .  61
   Authors' Addresses. . . . . . . . . . . . . . . . . . . . . . . .  61
   Full Copyright Statement. . . . . . . . . . . . . . . . . . . . .  62

1.  Introduction

   The Multicast Listener Discovery Protocol (MLD) is used by IPv6
   routers to discover the presence of multicast listeners (i.e., nodes
   that wish to receive multicast packets) on their directly attached
   links, and to discover specifically which multicast addresses are of
   interest to those neighboring nodes.  Note that a multicast router
   may itself be a listener of one or more multicast addresses; in this
   case it performs both the "multicast router part" and the "multicast
   address listener part" of the protocol, to collect the multicast
   listener information needed by its multicast routing protocol on the
   one hand, and to inform itself and other neighboring multicast
   routers of its listening state on the other hand.

   This document specifies Version 2 of MLD.  The previous version of
   MLD is specified in [RFC2710].  In this document we will refer to it
   as MLDv1.  MLDv2 is a translation of the IGMPv3 protocol [RFC3376]
   for IPv6 semantics.

   The MLDv2 protocol, when compared to MLDv1, adds support for "source
   filtering", i.e., the ability for a node to report interest in
   listening to packets *only* from specific source addresses, as
   required to support Source-Specific Multicast [RFC3569], or from *all
   but* specific source addresses, sent to a particular multicast
   address.  MLDv2 is designed to be interoperable with MLDv1.

Vida & Costa                Standards Track                     [Page 2]
RFC 3810                     MLDv2 for IPv6                    June 2004

   The capitalized 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].  Due to the lack of italics, emphasis is indicated herein
   by bracketing a word or phrase in "*" characters.  Furthermore,
   square brackets are used to denote the value of the enclosed
   variable, as opposed to the variable itself, written without
   brackets.

2.  Protocol Overview

   This section gives a brief description of the protocol operation. The