[cisco-voip] SIP Issue

[Jason Granat]

This is a little off-topic but to me still relevant in my learning process. I'm not looking for someone to solve this specific problem, in and of itself. I need to know if I am doing something wrong. I want to understand the technology. I have a voice lab to pass, you know... :)

Sooo... I've had this issue with a UC520. On CME 7.x or greater I have an issue with outbound calls through my SIP carrier having one-way audio, only when 'service phone videoCabaility' is set to 1 under telephony-service. This does not happen on CME 4.2 or lower. I ran some tests. This is all 100% reproducible every time. I am trying to pinpoint this thing with sub-nanometer precision...

Here's the basic layout. UC520 with skinny phones (796X & CIPC) with CUVA ball cams. SIP trunk to CallCentric. When the video option is off globally in telephony-service (service phone videoCapaility 0) all calls are fine. When video is enabled (service phone videoCapaility 1) calls from the skinny phones out to PSTN via CallCentric have one-way audio: the called party hears just fine but the calling party has dead air. No rx on the phone. Wireshark confirms no RTP coming back to the phone, yet signaling does. All other calls are fine, internal to internal, PSTN to internal.

I started my testing by rebooting the UC520 without modifying the config. When it came back up I was able to make outbound calls several times with 100% success, with the 'service phone videoCapability' set to 1. After roughly 5 minutes of uptime I went from 100% success to 100% failure. I rebooted again, same behavior:  5  minutes of 100 % outbound calling success, followed by 100% failure.

1'st sanity check: while it was working I copied the running config to tftp as a 'good' file. After it started failing I copied the running config to tftp as a 'bad' file. A diff on the two showed no differences. The config doesn't change between 'good' and 'bad'.

2'nd sanity check: I added the entire list of CallCentric supported codecs to my 'voice class codec'. When the call works it negotiates G711uLaw. As soon as the problem starts happening the call starts negotiating at G729r8. The call setup completes, yet one-way audio.

3'rd sanity check: I set 'service phone videoCapability' back to 0, create cnf-files, reset phones and things work again, always, without rebooting. This parameter is the only thing that changes to break or fix the issue.

4'th sanity check: I watched system uptime with the 'version' command. The problem ALWAYS starts happening at the 6 minute mark.

5'th sanity check: This only happens with IOS post 12.4(11)XW10, which has CME 4.2(0). If I roll back to 12.4(11)XW10 the problem never happens, whether video is enabled or not... NEVER!!! In fact I can only have the G711uLaw codec in my list and it still works flawlessly on this code... IOS post this release is CME version 7.x...

Aaaarrrgghhhh.....


TIA...

Jason

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