Subject: I-D ACTION:draft-mattson-multicast-2547bis-00.txt

From: [email-masked]
Date: Mon, 28 Jul 2003 11:06:22 -0400

A New Internet-Draft is available from the on-line Internet-Drafts directories.

	Title		: Multicast Group Membership Update over 2547bis VPNs
	Author(s)	: G. Mattson
	Filename	: draft-mattson-multicast-2547bis-00.txt
	Pages		: 0
	Date		: 2003-7-28
	
[RFC2547-bis] is a peer-to-peer VPN model allowing customers to establish unicast routed connectivity over L3 VPNs. But [RFC2547bis] does not provide a means for customers to establish multicast distribution trees over these VPNs. This text proposes a simple means for supporting multicast over [RFC2547-bis] VPNs. The solution is generic and can be used with most multicast IGPs (M-IGPs) including PIM-SM, PIM-DM, IGMP proxy and CBT.

The proposed technique allows a PE to act as a gateway between multicast M-IGP peers in the CE and the MBGP-based VPN. The PE maintains an M-IGMP peering relationship with an M-IGP agent at the CE. Through the M-IGP peering session the PE receives group membership information. The PE gateway exports this membership information to BGP. The information is then conveyed to the appropriate far-end PE by means of MBGP with proposed extensions. The far-end PE imports this membership information and acts on it according to the rules of the M-IGP it is supporting. In general the far-end PE will setup/teardown a forwarding entry for this group and pass the join/prune information toward the source. 

In order, to keep this protocol simple, this solution is directed only at the Source-Specific Multicast service model, but is structured in a way that does not explicitly preclude future expansion to cover the Any-Source Multicast service model. 

Another simplifying assumption regards the topology of the VPN. Multicast protocols are often designed with the assumption that the IGP routing on which it is based is symmetrical throughout the network. The proposal maintains this assumption. The solution is not necessarily applicable to all the possible multi-level, overlapping, asymmetrical VPN topologies that are possible within [2547-bis]. Rather, this proposal is directed at the fully-meshed VPNs with symmetrical routing metrics at each PE.

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