Multicast Address Use in AG2
Ivan R. Judson
judson at mcs.anl.gov
Tue Feb 11 04:34:44 CST 2003
I promised a plan, but here is a bit more than that. I'm going to describe
the problems and put forth a solution.
The problem we have is the following:
- AG 1.0 used statically assigned multicast addresses for the media (e.g.
one address for video and one address for audio).
- There has been some work at making sure this set of addresses work,
including various firewall, bridge, and tunneling solutions.
- AG 2.0 uses dynamically assigned addresses for media by default, however
static addressing is supported. The static address support should ensure
events like SCGlobal can succeed. We're moving to dynamic addressing because
there is a limited IPv4 multicast address space and we plan on creating
competition for that resource by making Virtual Venues so simple to host
that they are everywhere (as many as web pages? That'd be cool)
- We can't support infinite backwards compatibility, but want to support
backward compatibility enough for users to comfortably transition (we don't
want to abandon the community!)
- We're moving to dynamic addressing, but before we can do entirely dynamic
address allocation we need to ensure the basic services are fault tolerant
and robust enough to handle the problems associated with network brokenness.
- During the transition we need the right solution so the community can
transition comfortably from AG1.0 to AG2.0.
So, what do we do?
1) AG2 will incorporate functionality to statically configure a Virtual
Venue with audio and video media streams. These statically configured
streams are AG1 compliant streams (ie, H.261 video or 16bit, 16KHz
2) We will host a transitional AG2 Venue Server that is initialized with the
AG1 venues (same name, description, topology, and media streams) so that AG2
users can collaborate with AG1 users. We will get this built as soon as
3) We will transition along the following timeline:
- On or near September 15th we'll turn off the existing Virtual
- On or near November 31st, we'll stop supporting the transitional
If there are any questions or concerns, please don't hesitate to send email
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