[cisco-voip] H.323 MTP Usage

[Ryan Ratliff]

What codec is getting used for the calls through the MTP?  The software MTP only supports g.711 and if you are using any other codec CUCM will try to allocate a transcoder and this part sounds like it is failing based on your description.

-Ryan

On Apr 27, 2010, at 7:58 AM, Tom Mc wrote:

> Hi guys,
> 
> I have a query about how mtp can be implemented with h.323 gateways.
> 
> We are going through a migration for a customer replacing a LCR solution.
> Topology looks something like this:
> PBX --> QSig --> 3845 --> H.323 --> CUCM 7.1 --> H.323 --> 3845 --> QSig --> PBX
> CUCM has been configured for call routing using route patterns with
> h.323 gateway destinations
> 
> This solution has been implemented internationally for about 40 sites
> all with 'any to any' connectivity which has not been a problem.
> We now need to cutover Australia, and I have just been told that
> routing to the other 40 sites at this point in time is not possible
> and that media traffic will need to be routed via the CUCM cluster.
> 
> I've tried to lab up this solution (replacing the pbx with ip phones)
> trying to get the gateways to use an MTP (which is registered) and
> thus forcing the media stream out to the internationally hosted CUCM
> cluster.
> 
> Ticking the box "Media Termination Point Required" in the gateway
> config and assigning a MRGL with the CUCM software MTP's does not seem
> to work.
> Wireshark shows the media stream from GW to GW not GW to CUCM to GW as expected.
> Setting the service parameter  "Fail Call If MTP Allocation Fails" to
> true, predictably ends the call on answer attempt.
> 
> Is what I am attempting to do possible with the CUCM software MTP's?
> Do I need hardware resources to do this?
> 
> The "Help, this page" on the gateway config page tells me the
> following (which sort of tells me that this is not the purpose of the
> MTP):
> 
> "If you want a Media Termination Point to implement features that
> H.323 does not support (such as hold and transfer), check the check
> box.
> 
> Use this check box only for H.323 clients and H.323 devices that do
> not support the H.245 Empty Capabilities Set message.
> 
> If you check this check box to require an MTP and this device becomes
> the endpoint of a video call, the call will be audio only."
> 
> 
> Cheers,
> Tom
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