SIP Trunk + Transcoder understanding

[drbabbers]

All,

I was wondering please for a bit of fundamental help understanding a call flow involving an ITSP and a codec mismatch, with the possible use of a transcoder. The transcoder part is what I am mainly interested in understanding.

If we go with this call setup as an example:

HQ PHONE<--------CUCM<---------SIP TRUNK<--------CUBE<--------------ITSP<-------PSTN PHONE

<----------------------------------------------INBOUND CALL FROM PSTN TO HQ PHONE-----------

• The phone and SIP Trunk are in a Device Pool + Region that only supports g729
• CUBE is setup with the only permitted codec being g729
• An INVITE comes in from the ITSP to the CUBE with an early offer of g711 only
• For the inbound call leg we have a codec mismatch between CUBE and the ITSP

My questions are...

• I assume normally the call will fail with a media negotiation issue?
• Can I implement a local transcoder on the CUBE to fix this situation? (Standalone and not registered with CUCM?) Therefore we have a media stream between CUBE and the ITSP in g711 and a media stream between CUBE and the HQ PHONE in g729?
• If the transcoder can assist, then will the SIP call successful with what the ITSP are offering? So in this case g711 is negotiated in the call setup end to end?
• Is a transcoder invoked at the 'problem end' of the call leg? For example the CUBE here can't support what the ITSP are offering.

Your help is much appreciated! I would love to lab this but don't have a spare CUBE laying around :-)

Thanks

D

[Dennis Mink]

there is probably no silver bullet, but if you cant change the codec negotiation to include G711 end to end then yes, XCODE will be a necessity.

CUBE;s can do local transcoding without an SCCP dependency on CUCM:

http://www.cisco.com/c/en/us/support/docs/voice-unified-communications/unified-border-element/100480-cube-transcode.html

the requirement for this is that the CUBE is in flow through. which means ALL RTP streams go though the CUBE.

Please rate if useful

[Devansh]

please configure a universal transcoder. this will eliminate sccp protocol.