draft-ietf-magma-mld-source-04.txt   draft-ietf-magma-mld-source-05.txt 
MAGMA Working Group B. Haberman MAGMA Working Group B. Haberman
draft-ietf-magma-mld-source-04.txt Caspian Networks draft-ietf-magma-mld-source-05.txt Caspian Networks
Expires June 2003 December 2002 Expires August 2003 February 2002
Source Address Selection for Multicast Source Address Selection for Multicast
Listener Discovery Protocol (RFC 2710) Listener Discovery Protocol (RFC 2710)
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Abstract Abstract
It has come to light that there is an issue with the selection of a It has come to light that there is an issue with the selection of a
suitable IPv6 source address for Multicast Listener Discovery suitable IPv6 source address for Multicast Listener Discovery
messages when a node is performing stateless address messages when a node is performing stateless address
autoconfiguration. This memo is intended to clarify the rules on autoconfiguration. This memo is intended to clarify the rules on
selecting an IPv6 address to use for MLD messages. selecting an IPv6 address to use for MLD messages.
This document updates RFC 2710.
Introduction Introduction
The original specification of the Multicast Listener Discovery The original specification of the Multicast Listener Discovery
Protocol[RFC 2710] mandates the use of a link-local IPv6 source Protocol[RFC 2710] mandates the use of a link-local IPv6 source
address for the transmission of MLD messages. In addition, MLD also address for the transmission of MLD messages. In addition, MLD also
requires nodes to send MLD Report messages when joining any IPv6 requires nodes to send MLD Report messages when joining any IPv6
multicast group (except the All-Nodes address and addresses of scope multicast group (except the All-Nodes address and addresses of scope
less than 2). less than 2).
These MLD requirements conflict with the use of IPv6 multicast within These MLD requirements conflict with the use of IPv6 multicast within
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MLD Report and Done messages are sent with a link-local address as 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 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 interface. If a valid link-local address is not available (e.g. one
has not been configured), the message is sent with the unspecified has not been configured), the message is sent with the unspecified
address (::) as the IPv6 source address. address (::) as the IPv6 source address.
Once a valid link-local address is available, a node SHOULD generate Once a valid link-local address is available, a node SHOULD generate
new MLD Report messages for all multicast addresses joined on the new MLD Report messages for all multicast addresses joined on the
interface. 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.
Source Address Selection Implications Source Address Selection Implications
In RFC 2710, MLD Report and Done messages are required to have an 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 IPv6 source address that is link-local. This memo augments that rule
by allowing these messages to contain the unspecified address (::) as by allowing these messages to contain the unspecified address (::) as
the source address. the source address.
The behavior of RFC 2710 implementations, when receiving a message The behavior of RFC 2710 implementations, when receiving a message
with a source address of ::, is dependent upon how the implementation with a source address of ::, is dependent upon how the implementation
treats the unspecified address. That is, these messages will be treats the unspecified address. That is, these messages will be
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As the unspecified address is only used when there is no link-local As the unspecified address is only used when there is no link-local
address, RFC 2710 implementations discarding these packets will have address, RFC 2710 implementations discarding these packets will have
no affect on the packet's sender as the use should only be for no affect on the packet's sender as the use should only be for
joining the link-local solicited-node multicast group [RFC 2462]. joining the link-local solicited-node multicast group [RFC 2462].
There is an implication to senders with respect to joining other There is an implication to senders with respect to joining other
multicast groups prior to the activation of a link-local address. multicast groups prior to the activation of a link-local address.
The dropping of Reports using the unspecified address as a source The dropping of Reports using the unspecified address as a source
address could cause a lack of multicast traffic that is expected by address could cause a lack of multicast traffic that is expected by
the node. This black hole will be termporary until the node can send the node. This black hole will be temporary until the node can send
a Report with a valid link-local address. a Report with a valid link-local address.
Security Considerations Security Considerations
General security issues related to MLD are discussed in [RFC 2710]. General security issues related to MLD are discussed in [RFC 2710].
The ability to send MLD messages with the unspecified address can The ability to send MLD messages with the unspecified address can
lead to on-link abuse that is harder to trace. However, due to the lead to on-link abuse that is harder to trace. However, due to the
expected behavior of RFC 2710 implementations to drop these messages expected behavior of RFC 2710 implementations to drop these messages
and the additional rule that Query messages with the unspecified and the additional rule that Query messages with the unspecified
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1998. 1998.
[RFC 2462] Thomson, S., Narten, T., "IPv6 Stateless Address [RFC 2462] Thomson, S., Narten, T., "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998. Autoconfiguration", RFC 2462, December 1998.
Author's Address Author's Address
Brian Haberman Brian Haberman
Caspian Networks Caspian Networks
One Park Drive One Park Drive
Suite 400 Suite 300
Research Triangle Park, NC 27709 Research Triangle Park, NC 27709
Phone: +1-919-949-4828 Phone: +1-919-949-4828
EMail: bkhabs@nc.rr.com EMail: bkhabs@nc.rr.com
Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
the copyright notice ore references to the Internet Society or other the copyright notice ore references to the Internet Society or other
Internet organizations, except as needed for the purpose of Internet organizations, except as needed for the purpose of
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