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Multicast traffic effect on data network

This is more of a conceptual question I think. Recently I was called in to a client site to install a new 2600 Router, PIX firewall, and an IDS system (along with a bunch of other server side work). Anyways, I happened to do a few packet captures at that point which turned out to be a blessing. Now, fast forward a few weeks, the project is completed;however, over the course of the last few weeks, they also had a voice over IP system installed during that time. I will be the first to admit my own ignorance of VoIP systems (especially 3Com), but I wasn't concerned because the VoIP system was from the begining going to utilize it's on network infrastructure. In other words..the Voice and Data networks would never meet. To make a long story longer..the weekend of the install, they informed us the only way it will work is to have all of it running over the same network (Voice and Data all on the same subnet). This VoIP system is generating a ton of multicast packets. It went from 1.5 multicast packets /s previous to the phone system install to 45 multicast packets per second after the install. Now the client is complaining about occasional performance problems on the data network. I can't find anything wrong with the equipment that would account for these issues (10 or so second delays accessing network resources and such) question is simple if long winded...

45 packets isn't alot when I consider some of the broadcast storm scenario's i've seen, but then again in a broadcast storm, the whole network would come down. Is 45 packets per second multicast enough to affect system performance in a production environment? It seems like it would to me in my experience..What do you think?? I wish I could tell them to turn the phones off for a day, but obviously that's not possible. Anybody got any good multicast documents concerning how it affects data networks? any ideas would be greatly appreciated.


Re: Multicast traffic effect on data network

Actually, it might depend on the hardware resources on the network devices and the bandwidth available. But, anyhow I don't think 45 packets per second is too large, if there are no loops.

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Re: Multicast traffic effect on data network


I think it is something wrong there.

for 1 call in G729 there is only 30 pps

have u capture what is it ?

what is the diagram ?

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