Transcoder Query

[Ayodeji Okanlawon]

Hi guys,

I am seeing some interesting transcoding events on my cluster..

Calls between eg unity connection and Cube gateway even though set to use G711 bothways are invoking a xcoder resource..

This is a sh sccp connection

sess_id    conn_id      stype mode     codec   sport rport ripaddr
536953668  469829856    xcode sendrecv g711u   17822 32224 172.16.80.89
536953668  469829855    xcode sendrecv g711u   19442 17824 172.16.80.10
536953733  469830509    xcode sendrecv g711u   16426 18648 172.16.80.120..unity connection server
536953733  469830508    xcode sendrecv g711u   16386 29870 172.16.80.104

sh sccp all revealed this.

sess_id    conn_id    call-id    codec   pkt-period dtmf_method    type        bridge-info(bid, cid)   mmbridge-info(bid, cid) srtp_cryptosuite          dscp  
536953733  -          165022     N/A     N/A                 rfc2833_pthru     transmsp  All RTPSPI Callegs      N/A                     N/A                       N/A   

536953733  469830509  165023     g711u   20         rfc2833_pthru     rtpspi    (111780,165022)          N/A                     N/A                       184  

536953733  -          165022     N/A     N/A        pthru_report      transmsp  All RTPSPI Callegs      N/A                     N/A                       N/A   

536953733  469830508  165021     g711u   20         pthru_report      rtpspi    (111739,165022)          N/A                     N/A                       184  

As you can see from the output of sh sccp all and sh sccp connection, these calls use same codec and yet invoke a xcoder resource.

Is there any reason for this?

[Chris Deren · Accepted solution]

This is probably because an MTP is needed for DTMF, etc, Xcoder can do some MTP functionality and CUCM will allocate it if it's available in the MRGL.  Adjust your MRGL to list Xcoders in seperate MRG and make sure that MRG is listed below an MRG with MTPs.

HTH,

Chris

[Ayodeji Okanlawon]

Chris,

I guess this was the case and I just wanted to be sure. I have looked a cucm traces and i have seen cucm requesting MTP for dtmf. The only thing that confused me was that i expect to see "MTP" as the device type on "sh sccp conn" and not "xcode"

[Chris Deren · Accepted solution]

That's the way CUCM works, it will use Xcoder in place of MTP if it is not prioritized accordingly via MRGL/MRG configuration.

Chris

[Ayodeji Okanlawon]

Chris, excellent!. One other thing i cant see to wrap my head around is that, on this device that is been used for xcoding (GW-XA), I have software MTP also configured on it. This device is not assigned to any MRGL, so its in the default group.

When cucm invokes MTP resource for the gateway (GW-CS) that needs it, it says that it cant find any resource in the gateway MRGL. In the MRGL, I have only xcoders and no MTP.

However it goes to GW-XA (which has a software MTP configured) in a default MRGL, and does not select MTP but the xcoder on it...Its strange. If its mtp it needs, it should use the mtp on it...Just a but lost as to why it cant use the xcoder on  gateway GW-CS for mtp and using the other gateway xcoder.

[Chris Deren]

Well, a transcoder for the most part can do eveything an MTP can do (there are things it cannot).  So, CUCM will allocate xcoder in MTPs place if it finds one. So your MRGL design needs to have a seperate MRG that includes the MTPs  listed before MRG that lists xcoder. This way MTP will be allocated when it needs to and xocder when it needs to as MTP on the other side cannot do xcoding.

HTH,

Chris