MGCP Delayed Audio at branch location

[heathbaskin]

We have one location that is complaining that when making or receiving a call, when answered, there is no audio for about 3-5 seconds. This happens on random calls throughout the day and extremely inconsistently. This can happen with calls onsite onnet. So phone A dials phone B and both are located and registered to the local branch location. When phone B answers, neither hear audio for about 3-5 seconds. I'm thinking this has to do with call setup packets between the phones and the remote call manager server they are registered to. However, bandwidth utilization at the site is low so contention shouldn't be an issue. This is the only site out of hundreds that have this issue which leads me to believe it is either local to the data circuit or the router/switch config. Has anyone else dealt with similar experiences?

[George Thomas]

Weird issue, could you tell us what call control - CUCM/CME, version, phones, firmware version? Is this issue happening on phones on the same switch?

[heathbaskin]

MGCP gateway, SCCP phones. CUCM ver 7.1.5 but will be moving to 9.1 and going to a SIP gateway.

Phones are 79xx series phones. Latest firmware supported for 7.1.5.

Yes, the issue occurs on-net even within the same switch.

I have a TAC case open and based on the logs, he thinks the call setup request is being sent on the data vlan and the phone is not responding, then timing out.  CUCM re-sends the request and then the phone responds and sets up the RTP stream.  

We've had bad luck doing wireshark captures to truly lock down the issue.

Sorry for the delay in response.