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VOIP using cRTP

I am using cRTP on the VOIP path. There is a cisco 7206 VXR on one end of the 1 Mbps duplex satellite link and a cisco 3640 at the other end of the satellite.

The problem is that when enabling cRTP /head-compression on passive and non-passive mode, I am seeing traffic imbalance on both the input and output rate. I thought that given the symetrical nature of the VOIP traffic, I should see about the same amount of traffic on input or output. In my situation, when doing a show interface on my serial (with a 30s load interval), I am seeing that the input rate is twice the output rate.

When I disabled the cRTP, the input/output rates are almost the same.(+/- 6k)

Had anyone experienced similar problem when running cRTP with the Frame-relay encapsulation over a satellite link or terrestrial link ?

Also I have increased the number of concurrent compresed conversation to the max of 256 and was wondering if this could cause any problem on the voice quality ?

Please help clarify and suggest fix thanks.



Re: VOIP using cRTP

Since there has been no response to your post, it appears to be either too complex or too rare an issue for other forum members to assist you. If you don't get a suitable response to your post, you may wish to review our resources at the online Technical Assistance Center ( or speak with a TAC engineer. You can open a TAC case online at

If anyone else in the forum has some advice, please reply to this thread.

Thank you for posting.

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