draft-ietf-magma-mld-source-05.txt   draft-ietf-magma-mld-source-06.txt 
MAGMA Working Group B. Haberman MAGMA Working Group B. Haberman
draft-ietf-magma-mld-source-05.txt Caspian Networks draft-ietf-magma-mld-source-06.txt Caspian Networks
Expires August 2003 February 2002 Expires December 2003 June 2003
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
skipping to change at page 2, line 38 skipping to change at page 2, line 38
detection. detection.
In addition, Sections 5 and 6 of [RFC 2710] mandates that a node In addition, Sections 5 and 6 of [RFC 2710] mandates that a node
receiving an MLD Report message verify that the IPv6 source address receiving an MLD Report message verify that the IPv6 source address
is a link-local address. This document relaxes this rule in order to is a link-local address. This document relaxes this rule in order to
support the alternative IPv6 source address in use during duplicate support the alternative IPv6 source address in use during duplicate
address detection. address detection.
The discrepencies in the rules defined in [RFC 2710] and [RFC 2462] The discrepencies in the rules defined in [RFC 2710] and [RFC 2462]
has led to implementation issues. Several IPv6 implementations skip has led to implementation issues. Several IPv6 implementations skip
sending MLD Report messages during duplicate address detection. This sending MLD Report messages during duplicate address detection
leads to operational problems when a node is attached to switches because they have no valid link-local address. This leads to
that perform MLD snooping. In this scenario, duplicate address operational problems when a node is attached to switches that perform
detection will complete successfully and collisions occur once the MLD snooping. In this scenario, duplicate address detection will
address is put into use. These rules will allow implementations to complete successfully and collisions can occur once the address is
correctly implement duplicate address detection and operate in the put into use because switches may not have forwarded the DAD messages
described environment. 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 MLD Source Address Selection Guidelines
An MLD speaking node is required to choose a suitable IPv6 source An MLD speaking node is required to choose a suitable IPv6 source
address for all MLD messages (Report, Done, and Query). address for all MLD messages (Report, Done, and Query).
MLD Query messages MUST be sent with a valid link-local address as 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 the IPv6 source address. If a node (router or host) receives a query
message with an IPv6 source address set to the unspecified address message with an IPv6 source address set to the unspecified address
(::), it MUST silently discard the message and SHOULD log a warning. (::), it MUST silently discard the message and SHOULD log a warning.
skipping to change at page 3, line 22 skipping to change at page 3, line 29
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 Routers receiving an MLD Report or Done message with the unspecified
address as the IPv6 source address MUST silently discard the packet address as the IPv6 source address MUST silently discard the packet
without taking any action on the packets contents. 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 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
skipping to change at page 3, line 42 skipping to change at page 4, line 4
dropped if the implementation does not consider the unspecified dropped if the implementation does not consider the unspecified
address to be link-local in scope. address to be link-local in scope.
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 temporary 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 For hosts and routers, all received MLD messages from an unspecified
lead to on-link abuse that is harder to trace. However, due to the source address are silently discarded. This is the required behavior
expected behavior of RFC 2710 implementations to drop these messages from [RFC 2710] and is not changed by this document. Thus, the
and the additional rule that Query messages with the unspecified changes have no new security impacts.
address be dropped, the impact of such messages will not affect
multicast capabilities on the link. 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 References
Normative References Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 2710] Deering, S., Fenner, W., Haberman, B., "Multicast [RFC 2710] Deering, S., Fenner, W., Haberman, B., "Multicast
Listener Discovery (MLD) for IPv6", RFC 2710, October Listener Discovery (MLD) for IPv6", RFC 2710, October
skipping to change at page 4, line 38 skipping to change at page 5, line 4
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 300 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: brian@innovationslab.net
Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society (2003). 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
 End of changes. 

This html diff was produced by rfcdiff 1.23, available from http://www.levkowetz.com/ietf/tools/rfcdiff/