HW conf bridge or transcoding?

Unanswered Question
May 7th, 2010

I have an environment with CUCM 7.1(3). Inside the LAN, we run g711 and people outside the company has IP Communicator running g729. Since SW conf bridge accept only g711, what is the best practice to enable conference with g711 and g729 streams: a HW conf bridge or transcoding on the routers?

I have this problem too.
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Jaime Valencia Fri, 05/07/2010 - 08:02

IMO either work

It would really depend on some questions.

Do you have a full DSP for HW CFB?

Or do you have some remaining channels but not a full DSP?

If you have a full DSP you can go with the HW CFB, otherwise you can only configure the XCODER

How often and how many users use CIPC for conference?

A HW CFB could be configured in a MRGL as 2nd option for the other users and they could use it as well, if you don't use XCODER anywhere else, they would only be used by CIPC users and only for a conference



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mnkojima Fri, 05/07/2010 - 08:13

Yes Java, I have full DSP's available. About MRGL with SW CFB as 1st and HW CFB as 2nd: if I have a conf with g729 and g711, will CUCM automatically allocate the HW CFB, or it will try to get the SW CFB since it is the 1st option?

Thank you for your help


Jaime Valencia Fri, 05/07/2010 - 08:16

It'll try whatever you have in the 1st MRG

You would need to modify the MRGLs, one for CIPCs with HW CFB in first place and one for the rest with SW CFB in first place.



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Aaron Harrison Fri, 05/07/2010 - 08:18

My personal preference is (assuming it suits the topology in general) to user a hardware transcoder at the CCM site, which is invoked when a G729 caller wants to join the software conference bridge on CCM.

Last time I looked (and this may have changed since) some things such as listing conference participants and removing them were supported on the software bridge but not on IOS.

It also means that you have transcoders available if (for example) you have UCCX or Unity running G711 (or other app servers) which tend to be on the same site as the CCMs.

If you have hardware conferences set up, you may still wind up in a position where someone tries to bring you (as G729) into an existing conference on the software bridge and it fails as you have no transcoders.

I would normally deploy a hardware conference bridge on remote sites with no CCM, where bandwidth is limited and it suits the operation of the business.


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mnkojima Fri, 05/07/2010 - 10:43

Thank you Aaron.

What do guys think about a mixed configuration: in the MRGL HW CFB as 1st option and SW CFB, and also XCODER. This way when I am without HW CFB available, g729 calls will be in the conf through XCODER.

Aaron Harrison Fri, 05/07/2010 - 16:00

That way you would need both xcode and cfb resources defined on the gateway which use physical DSP resource.

If you split it out, you dedicate all your hardware to xcoding, and use the software resource on CCM for the conferencing. Nice and simple, and predictable.



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