CODEC used in two phones in the same cluster if there is gatekeeper involved.

[Oak Ridge]

I have   gatekeeper controlled trunks configured in Call Manager.  What codec is used when my IP Phone  in region A  calls  another IP Phone B  in region B through the gatekeeper?

The signalling flow is this:

IP Phone A  ------Call Manager-------ICT Trunk A -------Gatekeeper------ICT Trunk B-----Call Manager-----IP Phone B 

ICT Trunk A is in device pool with region A.

ICT Trunk B is in device pool with region B.

Region A ----Region A: G711

Region B----Region B: G711

system default: G711

I know if there is no Gatekeeper involved, the CODEC of call between two phones is decided by "Region" setting.

[Carlo Poggiarelli]

Hi Oak.

Gatekeeper does call admition and it also check if there is enough bandwidth to let the call establish based on negotiated codec.

If a Phone A is in a Region A and a Phone B in a Region B and codec relation between Region A and B is G711, IP Phone A and B will establish a call using G711 codec until zone bandwidth value is enough to allow the call.

If you leave "use system default" value remember that IP Phones within the same Region will negotiate G711 , while IP Phones on different Regions will negotiate G729.

This because of the value of Default Intraregion Max Audio Bit Rate and Default Interregion Max Audio Bit Rate parameter defined in CUCM Service Parameters (default  64 Kbps and 8kbps respectively)

HTH

Regards

Carlo

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