[AG-TECH] AG -> SSM strategy

[Bill Nickless]

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An idea came up this evening, inspired by 
http://www.live.com/autotunneling.txt (which you should read anyway, but 
don't try to figure out how it relates to the rest of this note.)

Consider SSM, Source Specific Multicast.  SSM requires that the client 
software know the Source address and Group address for each Source of 
interest.  A client node, interested in traffic from a given 
(Source,Group), sends an IGMPv3 Join message including the (S,G) addresses 
and the network starts delivering the traffic.

How might this get bootstrapped in the context of the AG?

Well, we already know that AG nodes need to work with a Virtual Venue 
server.  This is a relatively fixed web server now.  Each Virtual Venue 
(virtual conference room) could have an associated (S,G) address.  The VV 
server would report this (S,G) address to interested AG nodes.

Here's the key idea: the AG nodes would join this VV (S,G) and receive 
periodic notifications of other active (S,G)s for the audio and video 
transmission from other AG nodes.  Each interested AG node would then join 
the (S,G)s for the audio and video streams it wants from the other AG nodes.

How would the VV server know what audio and video streams are 
available?  Each AG node would periodically (say, every 5 seconds) unicast 
their availability to the VV server, and the VV server would re-transmit 
those availability messages on the VV (S,G).

Because the stream availability would go through the VV server, the VV 
server could do several things.  First, it could encrypt the availability 
notices so that only the appropriate AG nodes with a key could decrypt them 
and know about active sources.  Second, it could look at the availability 
notices it receives and only rebroadcast those from authorized 
transmitters.  I'm sure we can think of other useful options.

The VV server would not have to maintain any state, because of the periodic 
nature of the source availability messages.  This simplifies the 
implementation considerably.
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Bill Nickless    http://www.mcs.anl.gov/people/nickless      +1 630 252 7390
PGP:0E 0F 16 80 C5 B1 69 52 E1 44 1A A5 0E 1B 74 F7     nickless at mcs.anl.gov

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