CODEC negotiation between different regions,locations and within the region.

[mahmoodmkl]

Hi,

I would really apprecaite if someone can clarify the below questions.

1.How does the IP Phone knows to use a particular CODEC(G.711) when it is communicating with another IP Phone which is in the same region.

2.The same as above but communicating with another IP Phone which is in different region.eg(G.729).

I might come up with some more questions once the above are answered.

Thanks

[Carlo Poggiarelli]

Hi.

When you add a IP Phone on the CUCM, you specify a Device Pool for it.

Within the DP, you specify the Region which is the decision maker for the Codec that IP Phone will use to communicate with another IP Phone within the same region (Because they are in the same DP or because all DP share same Region) or with another IP Phone of another Region.

Within the "System"-->> "Region" configuration menu, you can specify which codec phones should use for intra-region and inter-region communications, specifying "Region Relationship"

Keep in mind that by default, Intra-Region codec is G711 and Inter-Region is G729.

You can modify the default behaviour by changing "Default Intraregion Max Audio Bit Rate" parameter on "System"-->"Service Parameters" by selecting "Callmanager" Service and clicking on Advanced.

HTH

Regards

Carlo

[mahmoodmkl]

Hi,

Thanks for the information.

One last question,the above settings i mean the instruction to use certain CODEC is it delivered to the phone in the configuration file or ..?

Thanks

[Ayodeji Okanlawon · Accepted solution]

During media negotiation, CUCM informs the IP phones what codec to use and the IP address to send the media to. This is done after cucm has computed the capabilities relationship based on the regions the devices are in
 

[yadwindersingh]

Hi, i need some help 

I have a sceneries, we are using codec g729 for internal and external calls. And it is working fine. But in some cases we are unable to make calls on some specific numbers. CDR shows *bearier channel capabilities not implemented*. And if we change the codec to g711 we are able to make calls. 

So my question is why we are unable to call out using g729. Is there anything we can do to make calls using g729 instead of g711.

[Manish Gogna]

You may be calling out to certain endpoints / applications that do not support G729 like the Cisco Unity Express or others, in that case you will need a transcoder to make this work or get the codec changed to G711. if both parties can support G729 then it should not be an issue.

Manish

[yadwindersingh]

Trying to make PSTN Call on a mobile number...also when the same person call on ip phones we are unable to answere the call as phone keeps on ring while offhook.    Any suggestion

[Manish Gogna]

Hi,

When creating regions on cucm, you can specify the codec that it will use when talking with another regions or itself. if it is not specified then cucm instructs to use the following default region settings from the call manager service parameters:

Default Intraregion Max Audio Bit Rate   --- By default it is G722 / G711

Default Interregion Max Audio Bit Rate   ---- By default it is G729

HTH

Manish