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VTC issues

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jimfixit

MIS
Aug 5, 2003
116
US
our telecome group has purchased Polycom 7000 VTC HD units. The quality of the calls between two offices in the same building is great. Between units at opposite ends of our MPLS it is not so great. It can appear to be fine during tests and then when we go live it's all pixelated.

The polycoms have some stats indicating lots of jitter and high packet loss, but the switch ports on the internal network show 0 errors or drops, same with the routers between the offices. We've check our QOS policy map and the VTC service is not showing drops, we see the counters increase. We've gotten our carrier involved and they have stated they see the traffic and see no drops or errors. The checked the headers on the traffic and it is correctly tagged.

We can't reproduce the problem at will but it's pretty frequent. We can't tie it to amount of traffic, it will happen with testing in the middle of the night.

This has become very frustrating and there is a lot of finger pointing going on. The one thing I notice is that these VTC units, if you turn them off, lose all their settings such as IP address etc. So I question if they are really properly configured.

Right now, I'm trying to capture packets between two offices but I have zero experience in reading the protocols used by VTC. Wireshark expert info says it sees no errors but...we got some errors somewhere...we have to have. How do I find them so I can zero in on the cause?

I can post configs but there are a lot of units involved. And the same configs used to work fine with our older VTC units...it's these HD units that are giving us fits. Nothing in the network has changed. Maybe that's the issue. Maybe something should in order to correctly do HD?
 
finally found it. Had nothing to do with our network. Polycoms were set up for "basic" setting mode which does not give best quality end to end.

Incidentally found another issue: when putting it into high resolution, I guess it starts to use a different protocol. It looks the same a Gnutella and unfortunately our packet shaper would block that sort of stuff. So we had to change that tool to make VTC work right.
 
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