[AG-TECH] What's typical loss on multicast video/audio?

[Markus Buchhorn]

Hi John

>I have been reporting to my networking staff that I've been seeing losses on the order of 1-15% on my incoming multicast video/audio when participating in events and that those participating do report that they see some loss coming from me as well. Sometimes its only around 2-3% on average - other times its 5-10%.. and jumps up and down.

If things are going well, we get basically zero loss almost all of the time. The longer the path between you and the sender of course, the greater the chance of loss, and UDP makes it worse. 

I'd suggest running a beacon client and seeing if performance varies by 'network distance', which would give you a first order hint. You've sort of done this by moving around, but with the beacon the senders are in multiple locations so you don't have to be :-)
http://dast.nlanr.net/Projects/Beacon/

Something else to check, look at the CPU load on your receiver. One of the things we've found is that if the CPU load gets 'reasonably' high, then eventually vic fails to service the network buffer in time, and packets get dropped (overwritten) in the buffer - which vic reports as loss (rightly) but it isn't a network issue there.

Cheers,
        Markus


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