< draft-ietf-magma-mld-source-06.txt		draft-ietf-magma-mld-source-07.txt >
			A new Request for Comments is now available in online RFC libraries.
	MAGMA Working Group B. Haberman		RFC 3590
	draft-ietf-magma-mld-source-06.txt Caspian Networks
	Expires December 2003 June 2003
	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
	groups may also distribute working documents as Internet- Drafts.
	Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet- Drafts as reference
	material or to cite them other than as "work in progress."
	The list of current Internet-Drafts can be accessed at
	http://www.ietf.org/ietf/1id-abstracts.txt.
	The list of Internet-Draft Shadow Directories can be accessed at
	http://www.ietf.org/shadow.html.
	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.
	This document updates RFC 2710.
	Introduction
	The original specification of the Multicast Listener Discovery
	Protocol[RFC 2710] mandates 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
	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 when no link-local addresses are available.
	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].
	Justification
	In [RFC 2710], Section 3 requires that all MLD messages be sent with
	a valid link-local IPv6 source address. However, a node in the
	process of performing duplicate address detection for its link-local
	address will not have one available to use as a source address. For
	this reason, this document provides an alternative IPv6 source
	address for MLD messages being used during duplicate address
	detection.
	In addition, Sections 5 and 6 of [RFC 2710] mandates that a node
	receiving an MLD Report message verify that the IPv6 source address
	is a link-local address. This document relaxes this rule in order to
	support the alternative IPv6 source address in use during duplicate
	address detection.
	The discrepencies in the rules defined in [RFC 2710] and [RFC 2462]
	has led to implementation issues. Several IPv6 implementations skip
	sending MLD Report messages during duplicate address detection
	because they have no valid link-local address. This leads to
	operational problems when a node is attached to switches that perform
	MLD snooping. In this scenario, duplicate address detection will
	complete successfully and collisions can occur once the address is
	put into use because switches may not have forwarded the DAD messages
	to all nodes on the link as required. This document fixes this
	problem by specifying that MLD reports are to be sent using an
	unspecified source address prior to DAD being started in order to
	ensure that messages sent to LL multicast addresses (e.g., including
	MLD) are forwarded to all appropriate nodes as required.
	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 a node (router or host) 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 are sent with a link-local address as
	the IPv6 source address, if a valid address is available on the
	interface. If a valid link-local address is not available (e.g. one
	has not been configured), the message is sent with the unspecified
	address (::) as the IPv6 source address.
	Once a valid link-local address is available, a node SHOULD generate
	new MLD Report messages for all multicast addresses joined on the
	interface.
	Routers receiving an MLD Report or Done message with the unspecified
	address as the IPv6 source address MUST silently discard the packet
	without taking any action on the packets contents.
	Snooping switches MUST manage multicast forwarding state based on MLD
	Report and Done messages sent with the unspecified address as the
	IPv6 source address.
	Source Address Selection Implications
	In RFC 2710, MLD Report and Done messages are required to have an
	IPv6 source address that is link-local. This memo augments that rule
	by allowing these messages to contain the unspecified address (::) as
	the source address.
	The behavior of RFC 2710 implementations, when receiving a message
	with a source address of ::, is dependent upon how the implementation
	treats the unspecified address. That is, these messages will be
	dropped if the implementation does not consider the unspecified
	address to be link-local in scope.
	As the unspecified address is only used when there is no link-local
	address, RFC 2710 implementations discarding these packets will have
	no affect on the packet's sender as the use should only be for
	joining the link-local solicited-node multicast group [RFC 2462].
	There is an implication to senders with respect to joining other
	multicast groups prior to the activation of a link-local address.
	The dropping of Reports using the unspecified address as a source
	address could cause a lack of multicast traffic that is expected by
	the node. This black hole will be temporary until the node can send
	a Report with a valid link-local address.
	Security Considerations
	General security issues related to MLD are discussed in [RFC 2710].
	For hosts and routers, all received MLD messages from an unspecified
	source address are silently discarded. This is the required behavior
	from [RFC 2710] and is not changed by this document. Thus, the
	changes have no new security impacts.
	In the case of snooping switches, multicast forwarding state will be
	maintained based on Report and Done messages sent with the
	unspecified address as the source address. However, the security
	vulnerabilities in this scenario are similar to those describing
	forged messages in the security considerations section of [RFC 2710].
	References
	Normative References
	[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate		Title: Source Address Selection for the
	Requirement Levels", BCP 14, RFC 2119, March 1997.		Multicast Listener Discovery (MLD) Protocol
			Author(s): B. Haberman
			Status: Standards Track
			Date: September 2003
			Mailbox: brian@innovationslab.net
			Pages: 6
			Characters: 11554
			Updates: 2710
	[RFC 2710] Deering, S., Fenner, W., Haberman, B., "Multicast		I-D Tag: draft-ietf-magma-mld-source-07.txt
	Listener Discovery (MLD) for IPv6", RFC 2710, October
	1999.
	Informative References		URL: ftp://ftp.rfc-editor.org/in-notes/rfc3590.txt
	[RFC 2461] Narten, T., Nordmark, E., Simpson, W., "Neighbor		It has come to light that there is an issue with the selection of a
	Discovery for IP Version 6 (IPv6)", RFC 2461, December		suitable IPv6 source address for Multicast Listener Discovery
	1998.		(MLD) messages when a node is performing stateless address
			autoconfiguration. This document is intended to clarify the rules on
			selecting an IPv6 address to use for MLD messages.
	[RFC 2462] Thomson, S., Narten, T., "IPv6 Stateless Address		This document is a product of the Multicast & Anycast Group Membership
	Autoconfiguration", RFC 2462, December 1998.		Working Group of the IETF.
	Author's Address		This is now a Proposed Standard Protocol.
	Brian Haberman		This document specifies an Internet standards track protocol for
	Caspian Networks		the Internet community, and requests discussion and suggestions
	One Park Drive		for improvements. Please refer to the current edition of the
	Suite 300		"Internet Official Protocol Standards" (STD 1) for the
	Research Triangle Park, NC 27709		standardization state and status of this protocol. Distribution
	Phone: +1-919-949-4828		of this memo is unlimited.
	EMail: brian@innovationslab.net
	Full Copyright Statement		This announcement is sent to the IETF list and the RFC-DIST list.
			Requests to be added to or deleted from the IETF distribution list
			should be sent to IETF-REQUEST@IETF.ORG. Requests to be
			added to or deleted from the RFC-DIST distribution list should
			be sent to RFC-DIST-REQUEST@RFC-EDITOR.ORG.
	Copyright (C) The Internet Society (2003). All Rights Reserved.		Details on obtaining RFCs via FTP or EMAIL may be obtained by sending
			an EMAIL message to rfc-info@RFC-EDITOR.ORG with the message body
			help: ways_to_get_rfcs. For example:
	This document and translations of it may be copied and furnished to		To: rfc-info@RFC-EDITOR.ORG
	others, and derivative works that comment on or otherwise explain it		Subject: getting rfcs
	or assist in its implementation may be prepared, copied, published
	and distributed, in whole or in part, without restriction of any
	kind, provided that the above copyright notice and this paragraph are
	included on all such copies and derivative works. However, this
	document itself may not be modified in any way, such as by removing
	the copyright notice ore references to the Internet Society or other
	Internet organizations, except as needed for the purpose of
	developing Internet standards in which case the procedures for
	copyrights defined in the Internet Standards process must be
	followed, or as required to translate it into languages other than
	English.
	The limited permissions granted above are perpetual and will not be		help: ways_to_get_rfcs
	revoked by the Internet Society or its successors or assigns.
	This document and the information contained herein is provided on an		Requests for special distribution should be addressed to either the
	"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING		author of the RFC in question, or to RFC-Manager@RFC-EDITOR.ORG. Unless
	TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING		specifically noted otherwise on the RFC itself, all RFCs are for
	BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION		unlimited distribution.echo
	HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF		Submissions for Requests for Comments should be sent to
	MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.		RFC-EDITOR@RFC-EDITOR.ORG. Please consult RFC 2223, Instructions to RFC
			Authors, for further information.
End of changes. 14 change blocks.
	200 lines changed or deleted		38 lines changed or added
This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/