x-lite over the wan with CUCM 6.1.4

Answered Question
Apr 13th, 2010

I have a CounterPath X-lite sip softphone registered with our CUCM 6.1.4.  The soft phone works great when calling within my location.  I can call other SCCP phones and to our MCU audio conference bridge.  However, when I call DNs in different locations over the WAN the call does not complete.  X-lite dials fine and then the phone rings, but as soon as the remote end goes off-hook then the call is diconnected.

We have CUCM configured to use G729 across the WAN to different regions, but I would have thought that our SCCP phones would simply default back to G711 since X-lite only supports G711.

Questions...

1) Where can I find logs in CUCM that might help me troublehoot (aka where the debug command)?

2) Any idea why this call doesn't go through?

I have this problem too.
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Correct Answer by William Bell about 6 years 7 months ago

Tod,

Your assessment is the correct one. Because you have configured your inter-region voice CODEC to use G.729, the phones in the different regions will be unable to stand up the media stream. In other words, your calls are failing for the reasons you have already identified. If you go with the X-Lite pro, you can get the G.729 CODEC supported in the client and then you should be able complete your calls successfully. You only other alternative is to put X-Lite in a special device pool which has a special region that allows inter-region use of the G.711 CODEC.

Keep in mind that when CUCM refers to the audio CODEC they really mean the "best CODEC" not the "only CODEC supported". It is a subtle difference, but a difference nonetheless. It doesn't have an immediate impact on your scenario, but it is something to keep in mind. Also, with respect to SIP trunks, CUCM relies on the CODEC preferences in the SDP provided by the SIP-UA. Not sure how this plays with X-Lite as a client, but it may mean you will need to set a preference on CODEC choices. This assumes you decide to invest money into supporting the Counterpath product that you enjoy using and purchase the X-Lite pro.

HTH.

Regards,

Bill

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Correct Answer
William Bell Tue, 04/13/2010 - 18:00

Tod,

Your assessment is the correct one. Because you have configured your inter-region voice CODEC to use G.729, the phones in the different regions will be unable to stand up the media stream. In other words, your calls are failing for the reasons you have already identified. If you go with the X-Lite pro, you can get the G.729 CODEC supported in the client and then you should be able complete your calls successfully. You only other alternative is to put X-Lite in a special device pool which has a special region that allows inter-region use of the G.711 CODEC.

Keep in mind that when CUCM refers to the audio CODEC they really mean the "best CODEC" not the "only CODEC supported". It is a subtle difference, but a difference nonetheless. It doesn't have an immediate impact on your scenario, but it is something to keep in mind. Also, with respect to SIP trunks, CUCM relies on the CODEC preferences in the SDP provided by the SIP-UA. Not sure how this plays with X-Lite as a client, but it may mean you will need to set a preference on CODEC choices. This assumes you decide to invest money into supporting the Counterpath product that you enjoy using and purchase the X-Lite pro.

HTH.

Regards,

Bill

Tod Larson Wed, 04/14/2010 - 06:23

Bill,

Per your advice, I add the X-Lite phone to an existing device pool that uses G.711 to talk to all regions.  Then it worked perfectly.

I've learned that our Telepresence, Unity Voice Mail and  Meet-Me's have their own device pools in their own regions that talk only G.711.  Before I thought that the phone were just negotiating the G.711 codec.   This will help me in the future since we just got new conference phones that support G.722.  We'll have to create a new region for the G.722 code as well.

Thanks for the guidance.

Tod

William Bell Wed, 04/14/2010 - 06:34

Tod,

Actually, you won't need to create a new region for G.722 CODEC, your G.711 regions will support this (assuming you have CM service params and enterprise params set to the defaults). This gets into that "choose the best" discussion I had in my original follow up. From the CUCM/Region perspective, CODEC selection is derived from the intersection of CODECs supported by all entities involved in the media stream. The CODEC setting for a region or inter-region communication does not specify the exact CODEC that will be chosen. This setting identifies the best quality (highest bandwidth) CODEC that can be negotiated. An exception to this rule is iLBC. When this CODEC is specified and the inter-region Link Loss Type is set to “lossy” the iLBC CODEC is forced.

Now, G.722 has the same bandwidth requirements that G.711 has. So, as long as you have the G722 CODEC enabled in the Call Manager service parameter, have enabled G.722 advertisement in the Enterprise Parameters, and have phones that are allowed to advertise G.722 -- then you will find that two G722-capable phones that are talking to each other in a G.711 region will actually use G.722. This is because it is the "best quality" CODEC that can be negotiated.

HTH.

Regards,

Bill

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