[cisco-voip] SIP trunk one way audio

[Pawlowski, Adam]

Yes, I just went through this, this morning, with a SIP trunk through Asterisk to the CUCM. Without the MTP functioning, being in the right group/group list, and being enabled, DTMF does not work.

If you look at the SIP/SDP ACK that comes back from the call manager it will not contain the RTP 101 attribute for RFC2833 signaling and it flat out does not work. It won't say anything either as far as I can tell (CUCM 6.1.3.3190) because it is operator error having been setup that way.

That being set with Asterisk anyways (out of topic of this list but some people here use it with their SIP implementations) there were some bugs where that particular attribute was not being advertised to the callmanager despite being set, and it doesn't reply as being capable in that situation either. 

I'm not sure what the other out of band signaling is given "OOB" as the other option.

Adam Pawlowski
Network Analyst
University at Buffalo