[cisco-voip] H.323 MTP Usage

[Tom Mc]

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