[cisco-voip] CUCM MTP and g729

[Wes Sisk]

Interesting observations.

I am not aware of any changes around CM's software MTP only doing G.711.

The packet capture shows RTP coming into(?) to the MTP. I do not see any sign of anything egressing the MTP.

ccm has internal logic that attempts to connect RTP streams even if codec negotiation fails. This is controlled by a service parameter. You may be seeing an artifact of this behavior where no codec was common but the streams attempted to setup anyway.  Streaming codecs to the MTP that it does not support typically results in garble or silence on the egress leg.

/wes


On Jan 11, 2013, at 3:11 PM, Anthony Holloway wrote:

Hi All,

I have a wireshark capture off of my CUCM 8.6(2) which shows that it is receiving a g729 audio stream from my VG224.

Long story short, according to the CUCM SRND, the CUCM MTP can only terminate g711, and yet, attached is a screenshot of the wireshark capture which clearly shows it terminating g729.

What piece of this puzzle am I missing?  Also, the CUCM traces read like the MTP is being invoked on that CUCM.  It's due to the lack of the fm package on my VG224 and a mismatch in DTMF to the PSTN (SIP).  I had a fun time resolving that, as you can probably imagine.

Thanks and Happy Friday!


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