CUCM7 - Understanding Conferencing needs

Unanswered Question
Oct 16th, 2009


I currently have a CUCM7 site and some remote CUCME branches and PSTN gateways.

All the phones, in all the infrastructure use G.729 (even between phones in CUCM HQ).

For conferencing:

- between CUCM phones with G.729 i can make conferences (even knowing that Software Conference Bridge only supports G.711). Are this using Cisco IP Phones capabilities to make the conference?

- if i try to conference with remote CME IP Phones or PSTN users, it won't work. For this i'll need hardware conference resources? Can i tell CUCM to use remote gateways (CME and PSTN GW) resources to conference?

thanks in advance


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Jaime Valencia Fri, 10/16/2009 - 17:42

No, most probably you're using an XCODER or a HW CFB for them without noticing it.

You forcefully need to send G711 to the SW CFB so it mixes the streams.

You can allocate and instruct phone to use resources anywhere as long as you have them configured in CUCM and correctly configured MRG and MRGL.

Depending on who initiates the conference is which CFB is allocated.

I would suggest you to read the SRND chapter named media resources for further understanding



if this helps, please rate

metalium2007 Fri, 10/16/2009 - 23:39

How can i use an XCODER or an HW CFB without noticing it? I don't have it in MRG and MRGL.

Phones talking between them in G.729, registered in CUCM7 can conference without hardware resources. That works. Why? Is there any explanation?

(as long as i dont leave the CUCM domain, the conferences works in G.729)



Jaime Valencia Sat, 10/17/2009 - 18:19

The other explanation would be that someone explicitly configured the region between phones and SW CFB to be in G711

Do a simple test, make a conference call and see what codec the phone is talking in the call stats



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metalium2007 Mon, 10/19/2009 - 02:26

Yes indeed all other regions talk G.711 to Conference Bridge, since the CB doesnt support G.729.

Phones in HQ region can conference.

Phones in remote regions (that surely talk G.711 to CB too) don't conference (phones registered in CMEs and Legacy PBXs).

Is this the correct behaviour?

Thanks J.



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