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High Latency & Jitter from SIP-connected Fax Server

Hi everyone.

I have a new RightFax (OpenText) server being integrated with my UCM 7.1 cluster via SIP trunk. Outbound calls route through a MGCP-controlled PRI circuit located in the same building. I've set up both ends for T.38 encapsulation.

Functionally, call routing works in both directions. At the moment we're just working with outbound calls from the fax server, and we're finding transmission times are slower than via directly-connected T1s by factors of 2-5 times. Looking at CMR records there are extremely high values for Jitter (200+) and Latency (1000+), which surprises me since all of the infrastructure is in the same building.

My question is about the RTP data path for the fax transmission. In the CMR, it shows the destination device as the gateway, as expected, but the originating device is the SIP trunk as defined on UCM. Does this imply that the RTP stream traverses UCM? I would have thought that UCM would act the same way it does with phone/gateway calls where the RTP stream is set up between the endpoints.

I'm struggling with where to look to troubleshoot this.



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