Design consideration for UCCX

Unanswered Question
Sep 14th, 2009

I have two voice gateways at remote location and with three agents. I also have two gateways at central location with 12 agents.the central location hosts my Call Manager and UCCX. i have G729 configured between two sites.

Now Should i configure the UCCX for G711 or G729 Codec.

any help is appreciated.

I have this problem too.
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Jonathan Schulenberg Mon, 09/14/2009 - 05:59

You can technically do either but my recommendation is to always use G.711. IMO G.729 makes CCX too difficult to administer for most customers.

CCX will handle 100% of the calls in the configured codec, regardless of the regions in UCM. If the regions don't allow that codec, a transcoding resource must be invoked for the call.

Example 1: Call arrives on gateway at remote location. UCM locations specify G.729 is required but CCX is configured for G.711. UCM will invoke a transcoder at the central site for CCX.

Example 2: Call arrives at central site gateway. UCM indicates G.711 may be used within this site but CCX is running as G.729. If the gateway supports G.729, the call will be negotiated as that. If not, UCM will invoke a transcoder to translate from G.711 to G.729.

I tell customers that in the long run it ends up being easier to buy the DSPs necessary to transcode as needed than it is to deal with G.729 prompts on CCX. Unlike UCM, CCX does _not_ transcode the WAV files you give it. You must maintain all of your prompts in the codec you have set. Since G.729 is a licensed codec, it is more difficult to maintain your prompts as you cannot listen to them on your computer. You have to write an IVR script that allows you to record and play them back to you for review.

There is at least two valid counter-arguments to this advise (of course):

1) DSPs are not cheap.

2) This could result in tandem encoding/compression and degrade the MOS score and increase the delay of a call. Essentially this requires the assumption that you are the only one compressing this call. Tandem encoding/compression is not well understood by most but this document explains it. In essence, if any other point in the call path is also compressing the call, you're going to loose quality in a hurry. This probably isn't acceptable for a call center and gets especially interesting when you consider the residential VoIP services being offered now.

Understanding Delay in Packet Voice Networks - Effects of Multiple Compression Cycles

Abdulbaseer Mohammed Mon, 09/14/2009 - 15:12

It makes more sense to go with G711 for keeping things simple. I don't understand the depths of 711 vs 729 however given the number of agents/users on each G711 should be a better choice unless you have strong pressing rquirements otherwise.




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