One way audio for overseas calls

[eschroedorica]

I am having an odd problem. Ever since upgrading my CallManger cluster to 8.6, overseas calls (IE, to Australia) have only one way audio from the IP communicator. The caller, running the IP Communicator can hear the other party, but the other party cannot hear the caller.

I don't think it's a network configuration problem or a firewall issue, because internal, local, domestic LD, and LD to Canada all work perfectly.

We are running CM 8.6.2a, IP Communicator v8.6.1.0, and I have verified that the PSTN gateways are running a compatible IOS for callmanager 8.6.2.

I should mention that overseas calls made from a physical handset work just fine.

Has anyone ever seen this problem before?

[Chris Deren]

One way audio is 99% of the time related to routing issue.  Make sure that the data network the IPC is on has full routing to the voice network at the remote site and vice-versa.

Chris

[eschroedorica]

It does. Like I mentioned, this is all going through the same PSTN gateway, and everything other than overseas calls works fine.

[Udit Mehrotra]

Take a simaltaneous Packet Capture from CIPC and Voice Gateway. Make sure, no MTP is invoked. If you do not see any RTP from Phone to gateway, it is a routing problem. If you do see RTP being received on the gateway, contact your provider.

--

Udit

[eschroedorica]

Thanks everyone's replies. I think I found the issue.

For some reason, overseas calls were using the iLBC/G.728 codec, while all other calls were using G.729. I honestly have no idea why, because the codec used to communicate with the PSTN GW should be the same no matter where the destination is, to my understanding, seeing as the PSTN GW can only have one device pool associated with it.

In any case, I just changed all the region relationships for my softphone users' device pool to G.729. Problem solved.

[UC Support]

Hi Evan,

We have encountered the same problem, it seems is only when the call is thru a voice GW and uses iLBC codec, we have the one way audio, the IP Phone doesn't send packets (TX), the workaround is to use a G.729. I have seen the problem with:

Voice GW IOS 151-4.M2 and the following IP Phone models:

7937

796x

Weird thing the 69XX works OK with that config and the CIPC 8.6.1 works too. Also if we call between phones using iLBC it works fine, it's only when the call goes thru the voice GW.