Supplementary service on H.323

Unanswered Question
Feb 23rd, 2008
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I've CCM Pub and Sub with H.323 GW connecting to a gate keeper over WAN. Further, another H.323 GW to PSTN.


G.711 on Lan and G.729 on WAN. I've configured Software MTP, Conference bridge, Moh serves.

All supplementary services works internally (Conferencing, Transfer, Hold/resume), but when a g729 call is established with IP Phone, none of the supplementary service works. Putting an external caller on hold doesn't play moh and resuming it doesn't reconnect the caller back. The call gets disconnected after few seconds. Conferencing, Transfer also drops the caller.

I've selected G.711 and G.729 codec for Moh under Services parameters.

I tried making end-to-end G.729 still same problem.

Enabling MTP checkbox on CCM fails all external calls.

Packetization on CCM for G.729 is 20 ms and for G.711 is 30 ms.

SRND mentioned devices supporting H.323V2 doesn't required Hw MTP, and all supplementary features should work without any MTP profile on the GW.

I don't have DSP resources on GW therefore Conferencing G.729 calls won't work. But, Hold/resume an external call or Transfer an external caller should work in this scenario???

Don't have access to Gateway right now, basic inbound/outbound is working fine without any supplementary services.

Any suggestions are welcome.


Kapil Atrish

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kapil.atrish Sat, 02/23/2008 - 08:55
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I am on CCM 4.1.3 SR4d.

I checked if packetization period is different software MTP doesn't help, we need Hardware MTPs. But does that fit for G.729 calls also??

Packetization on CCM for G.729 is 20 ms and for G.711 is 30 ms.


Kapil Atrish

kapil.atrish Sun, 02/24/2008 - 01:17
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I think creating an enhanced IOS MTP will solve the hold & transfer issue faced with external calls without using hardware DSP resources. Sample as following:

dspfarm profile 1 mtp

description MTP for IPIPGW

codec g729r8

maximum sessions software 100

associate application SCCP

Howeve, I still need DSPs for Conferencing. Wondering how to configure the conferencing and software MTP on same router. Conferencing profile needs dspfarming, however software MTP needs dspfarming disabled.


Kapil Atrish

kapil.atrish Mon, 02/25/2008 - 21:56
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Has anyone faced the same issue? any suggestion are welcome..


Kapil Atrish


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