I've had this problem for a while and finally figured out the cause but not the fix.
I have a pair of 2651XM voice gateways at my main site. They are used to access PRI circuits as well as performing g.711/g.729 transcoding services for Unity. Note that Unity is configured to only accept g.711 calls.
Here is the problem. Packets from the voice gateway to phones are marked 101110 (DSCP EF). Packets from the same device but using the transcoder service are marked 101100 (DSCP ??).
Packets from Unity to x-coder are marked 101110
Packets to Unity from x-coder are marked 101100 <==== BAD!
Packets from phone to x-coder are marked 101110
Packets to phone from x-coder are marked 101100 <==== BAD!
Packets from phone to PRI gateway are marked 101110
Packets to phone from PRI gateway are marked 101110
How do I change the transcoder to use the right EF DSCP value? I'm running CM 4.1.3.