Subject: [Rmt] small group replication service, application-level multicast etc.

From: Rick Boivie <[email-masked]>
Date: Wed, 19 Mar 2003 12:55:22 -0500

Sally,
You mentioned the work that's been done in application-level multicast.
But this doesn't appear to be useful in solving the problem we're trying to
solve.

As I mentioned in the meeting on Monday, we're trying to solve the problem
of limited bandwidth in the first mile so that we can provide scalable
support for applications like VoIP conferencing, videoconferencing,
e-meetings in which there are likely to be very large numbers of
not-very-large groups.

In our view, the various multicast schemes (e.g. real multicast,
application level multicast) don't solve this problem very well since they
involve per-flow state and per flow signaling -- which, in our view, is not
the right model if one wants to support very large numbers of simultaneous
conferences.  We don't want to have to store state for tens of thousands or
tens of millions of distinct small groups and we don't want to have to
repair millions of distinct multicast distribution trees after a topology
change.

Does that make sense?

Rick Boivie

This problem of maintaining multicast state can be minimized in an
end-system multicast scheme if the multicast state is kept only in the
end-systems of the meeting participants.  But this approach doesn't seem
appropriate if we have limited bandwidth in the first mile (see problem
statement above).

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From: Justin Chapweske <[email-masked]>
Date: Wed, 19 Mar 2003 12:44:31 -0600

Actually, the Swarmcast system that we developed in late 1999 utilized 
Forward Error Correction combined with peer-to-peer (end-system) 
multicast to overcome the first-mile bottleneck in systems like this.

I'd be happy to discuss this approach off-line with anyone that is 
interested.

Thanks,

-Justin

-- 
Justin Chapweske, Onion Networks
http://onionnetworks.com/