SIP Load test

I am in the middle of programming a simple SIP load testing application where I generate x number of calls to a trixbox system and send the milliwatt 1k tone for t duration. Both x and t are currently manually changed in the application to match the needed load. The trixbox unit under test is currently recording all the calls so I can verify call quality by playing back the recordings.

Now the interesting part: If I set the call to last 2 minutes the subsequent recorded file has a duration for nearly 10 minutes??? The calls are confirmed to last the pre-configured duration via the CDR. Why is it transferring more data than it should? Or maybe I should ask How do I throttle the data flow to match a 64k voice stream? My assumption (also my first error is to assume), SIP and the codec would maintain the 64k rate to the recording.

Your input is greatly appreciated.

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