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Video Conferencing over ATM

We have a problem with video conferencing over ATM

Our company has two main branches with a WAN ATM connection.

A videoconferencing system is being implemented between the two sites.

We're are experiencing a bad performance of the video and audio stream , with lost frames .

The solution provider told us that the problem is in lost packets due to the ATM .

We asked the telecom provider and it says no packets were lost between the two site's routers

the topology is as follow

host----Cat2950--CAT5000----CISCO7500-----ATM-----CISCO7500----CAT5000---cat2924---host

_ What should be checked first to troubleshoot the problem?

_ Do the switches and routers need a particular configuration for videoconferencing be effective ?

_ Do the ATM interface on both routers need a specific configuration ?

_ Can spanningtree interfere with streaming video ?

Any help is greatly appreciated

Stefano Colombo

1 REPLY
Silver

Re: Video Conferencing over ATM

Stefano,

First of all you'll need to identify were you are having problems (i.e. Dropping traffic). "sh atm traffic" is a pretty good command to tell you if you having problems. If you see a lot of Oversized PDU's it might be due to your provider shaping/policing ATM cells and dropping them. If the ATM side is the issue you have many options for QOS that might help. If you have two PVC's (one for your normal traffic and one for video) you can look into PVC bundling which is a very good technique for IP to ATM QOS mapping. If not look into MQC or Service-policy which is modular QOS for IOS. Good stuff.

To answer your specific quesions:

What should be checked first to troubleshoot the problem?

Find out what is dropping packets. Check ATM (see above)

Do the switches and routers need a particular configuration for videoconferencing be effective ?

For End to End QOS, yes, they would. Ensure all duplex and speed settings are set correctly for starters.

Do the ATM interface on both routers need a specific configuration ?

See Above for MQC and Service-policy

Can spanningtree interfere with streaming video ?

Sure it could. If your STP problem occured on your 2950 - 5000 links it would interupt your video for up to 30 seconds during a spanning tree issue. Ensure your L2 environment is stable and with no issues. Need to remove this from your equation if possible. Reduce the moving parts if you know what I mean.

Hope this helps you on your way,

Don

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