MAGMA Working Group                                          B. Haberman
draft-ietf-magma-mld-source-00.txt                            Consultant
Expires March 2003                                        September 2002


                 Source Address Selection for Multicast
                 Listener Discovery Protocol (RFC 2710)


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
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Abstract

   It has come to light that there is an issue with the selection of a
   suitable IPv6 source address for Multicast Listener Discovery
   messages when a node is performing stateless address
   autoconfiguration.  This memo is intended to clarify the rules on
   selecting an IPv6 address to use for MLD messages.

Introduction

   The original specification of the Multicast Listener Discovery
   Protocol[RFC 2710] mandated the use of a link-local IPv6 source
   address for the transmission of MLD messages.  In addition, MLD also
   requires nodes to send MLD Report messages when joining any IPv6
   multicast group (except the All-Nodes address and addresses of scope
   less than 2).

   These MLD requirements conflict with the use of IPv6 multicast within
   the Neighbor Discovery Protocol[RFC 2461].  For stateless
   autoconfiguration, as defined in [RFC 2462], a node is required to



Haberman                                                        [Page 1]

INTERNET DRAFT                                            September 2002


   join several IPv6 multicast groups in order to perform Duplicate
   Address Detection prior to its use.  Since the only address the node
   has is tentative, and cannot be used for communication, it does not
   have a suitable address to utilize as a source address.

   This document will clarify the IPv6 source address selection rules
   for use with MLD.

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].

MLD Source Address Selection Guidelines

   An MLD speaking node is required to choose a suitable IPv6 source
   address for all MLD messages (Report, Done, and Query).

   MLD Query messages MUST be sent with a valid link-local address as
   the IPv6 source address.  If ia router receives a query message with
   an IPv6 source address set to the unspecified address (::), it MUST
   silently discard the message and SHOULD log a warning.

   MLD Report and Done messages SHOULD be sent with a valid link-local
   address as the IPv6 source address.  If a valid link-local address is
   not available, the Report MAY be sent with the unspecified address
   (::) as the IPv6 source address.

Security Considerations

   Security issues related to MLD are discussed in [RFC 2710].

References

   [RFC 2710] Deering, S., Fenner, W., Haberman, B., "Multicast Listener
              Discovery (MLD) for IPv6", RFC 2710, October 1999.

   [RFC 2461] Narten, T., Nordmark, E., Simpson, W., "Neighbor Discovery
              for IP Version 6 (IPv6)", RFC 2461, December 1998.

   [RFC 2462] Thomson, S., Narten, T., "IPv6 Stateless Address
              Autoconfiguration", RFC 2462, December 1998.

   [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.





Haberman                                                        [Page 2]

INTERNET DRAFT                                            September 2002


Author's Address

   Brian Haberman
   bkhabs@nc.rr.com

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Haberman                                                        [Page 3]