[AG-TECH] Question about multicast...

Markus Buchhorn Markus.Buchhorn at anu.edu.au
Thu Jan 15 19:19:17 CST 2004

At 15:45 15/01/2004 -0500, Sanders, Donell wrote:
>So I'm coming back to my office (well, really two cubes lined up against a big picture window in the new Computer Science Building) and my network guy asks me if we always connect to the same place when we start up the AG.  I'm thinking, "Hmmm.  That's a good question.  I only care if it doesn't work."  Am I right in thinking that we all connect to one place (the venue server) and then go our separate ways (to each venue) from there?  And if so, what is the IP address of this place?  Our network guy is trying to keep the AG traffic separate from the other "everyday" network traffic.  Or is it possible that we actually connect to whichever place that gets us to the venue server the "best" way or whatever?  Am I making any sense?  Just don't laugh at me too hard.

No laughter here, good questions.

The initial connection is unicast to the venue server (http/https), the address and port of which you select when connecting to the venue server (i.e.http://venues.<whatever>:<port>/...). The venue server returns information to your client about available venues, and what they have in them (varies by version of AGtk). 

So, that unicast traffic can be separated fairly easily. Not sure if there's much benefit in terms of performance, since it's basically small amounts of reliable-ish tcp traffic (the venue server itself is less reliable ;-) ).

A venue is identified as a set of multicast addresses and port numbers. So, your venue client tells the media tools (and whatever else you need) to point at certain multicast addresses. And that's basically it, barring the intra-node traffic between your audio/video/display machines.

You could ask the network guys to deliver multicast traffic differently to 'everyday' traffic, if that makes sense on your campus. We'll probably do that here for a while, for obtuse reasons :-)

Or they could store a (growing) list of venue addresses and just carve that off. Disadvantage of that is that one day the multicast addresses for venues will be dynamically allocated (unless Ivan/Tom and the gang have changed their mind).

There are some other traffic flows, such as the MOO/chat tool (unicast, to a specific address), but again these are small flows compared to the audio and video.

Does that help at all?


Markus Buchhorn, ANU Internet Futures Group,       |Ph: +61 2 61258810
Markus.Buchhorn at anu.edu.au, mail: Bldg #108 CS&IT  |Fx: +61 2 61259805
Australian National University, Canberra 0200 Aust.|Mob: 0417 281429

More information about the ag-tech mailing list