Infrequently, calls will not have audio in one direction.

Question

We're using OCS 2007 R2 with a Dialogic DMG2000 series gateway and Tanjay phones.  Occasionally, I have a user who might complain that an outbound call doesn't have audio in one direction or the other.  This happens once every few days.  I don't see errors anywhere and the Dialogic reports that there are no call issues.  The problem will clear up quickly and appears at random.  We still have the old PBX up, which also flows through the same Dialogic and does not experience the issue so I believe it's buried in OCS somewhere.
How can I being troubleshooting an issue like this?  Can someone point me in a direction?  I want my users to have as much confidence in this solution as possible.

Answer 1

One way audio issues have a few common root causes to check for:
1) Communicator users can sometimes mute speakers or mic on their PC without realizing it. Also If they have multiple audio devices attached then check they one they think they are using is really the one selected. Some devices also have local
mute buttons that get selected without the user realizing it.
2) Faulty devices can cause one way audio. Switch the device for one you know that works to test this or try using Sound Recorder to record a raw audio file and then play it back.
3) PSTN gateway configuration issues. This is a tougher one to troubleshoot, but if only OCS-PSTN calls are experiencing one way audio and it happens to many different users this is a likely cause. Check the codec configuration of GW means codec choices
with the Mediation Server match, i.e. G.711 u-law or G.711 a-law are preferred on both sides. Other configuration issues are vendor specific and so you may need their help verifying the Gateway is properly setup.
4) Less commonly network issues can cause one-way audio if there are serious routing or packet loss problems in one direction. You can look for signs of this in the QoE Server report of an affected call. The "PacketUtilization" metric records the packet
count for an audio stream. (You can find details of what indiviudal QoE metrics mean here -
http://technet.microsoft.com/en-us/library/dd819959(office.13).aspx). If further network troubleshooting is necessary you can try pings to see if network path is functioning and/or
collect network sniffs during an affected call.
There is a useful guide available to troubleshooting OCS VoIP issues here:
http://www.microsoft.com/downloads/details.aspx?familyid=7B490758-EF9A-4442-9F0F-A5AEB4935C46&displaylang=en