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ILBC and transcoding

Hi i want to use Cisco IP communicator with ILBC over vpn, so im performing a few tests and so far i just got ILBC running between 2 ip communicator without vpn, i know, no big deal, so i have a couple of questions

Im using call manager 7

i have assigned an softphone originating the call transcoding resources, this one calls a 7940 with the same MRGL asigned, they are registered on the same call manager, without VPN, who is invoking the transcoder, the 7940?

if i call to the pstn with the softphone, who is invoking the transcoder, the gateway?

and if im calling with the softphone via vpn to a 7940 in the central office=, who is invoking the transcoder?

Actually all of them use the same MRGL, and there are resources assigned to transcoding, but its no working, i dont know why, regions are properly configured, but when i place the call to the 7940 without vpn or to the pstn the codec used is g729, when i configured ILBC

any help is wellcome!!!!



Cisco Employee

ILBC and transcoding

Not many Cisco IP Phones support iLBC.

So when you trying calling a 7940 froma  IP Phone, they will negotiate a common codec. A codec which both of them support. CIPC supports most codecs. 7940 does support G711/G729 for sure.

So.. Depending on the CUCM region settings, a codec is negotiated. Only in cases were there's a total codec mismatch and no common codecs then transcoder is invoked.

Xcoder is usually invoked on the side which supports the high bandwidth. So if we have G729 on one side and G711 on another, the xcoder is invoked on the G711 side. So that G711 doesn't have to be transported over the WAN. ie if a WAN really exists in the network

Now with the GW, it depends on the type of the GW. If its a H323 GW, you can control the codecs using incoming dial-peers and voice class codecs.

Hope this makes sense


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ILBC and transcoding

Tahnks!!!, yes i think it makes sense

so, i have 2 diferent regions configured, A and B and the calls between them are set to use ILBC

if a softphone calls another softphone, they will use ILBC, because both of them support it

if a softphone calls a 7940 the will use g729, because is the one that they share

am i right?

so, how can i force the softphone to use ILBC whne calling "regular phones"?, because when i have this working i wan to to configure softphones using ILBC on the salesman laptops, and have them making calls throug VPN

thanks again!!!!



ILBC and transcoding

Hi Cesar,

You are right for softphone to softphone and softphone to 7940 IP Phone.

When calling to regular phones, I think you were refering to PSTN, you need to configure iLBC codec on dial-peers on the Voice GWs so that iLBC can be utilized. Again, it should be supported by your voice gateway IOS software.



With best regards...

ILBC and transcoding

Hi, thanks for your anwser,

Sorry i explain myself wrong, with "regula phones" i was meaning phisical phones, 79XX

thats exactly where my problem relies calls between softphone and phones 79XX not suporting natively ILBC, both of them registered on the same call manager group, being the softphone connected via VPN on a hotel room, for example, and a 7941 on the central office, how can i force ILBC on that case?

thanks a lot


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