Subject: [Softwires] Regarding draft-sarikaya-softwire-6rdmulticast-02.txt

From: "WRIGHT, STEVEN A" <[email-masked]>
Date: Fri, 2 Mar 2012 20:06:06 +0000

There is no address shortage in the IPv4 multicast address space, though it is nice to see completeness of support for multicast in 6rd.If I understand this correctly, this draft tunnels the IPv6 multicast stream as an AMT tunnel riding over the 6rd tunnel between the RG and 6rd BR. This has the disadvantage that it cannot leverage packet replication the in access network, which is potentially inefficient. It might be helpful if the document pointed out that limitation.
As a transition strategy that inefficiency may be ok, or if it is some new low bandwidth service. Current access equipment like DSLAMs do not support layer 3 Multicast completely, but it typically does support snooping on the IGMP messages and packet replication at layer 2. I believe some of the BBF specs provide a more complete description of this behavior.

Steven Wright, MBA, PhD.
Lead Member of Technical Staff

AT&T Services Inc.
Architecture & Planning
1057 Lenox Park Blvd NE, STE 4D28
Atlanta, GA 30319
P: 404.499.7030

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