h323 supplementary services

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Mar 30th, 2007
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Hello, I came into this issue and hope someone can help me.

I have a Callmanager 4.2, connected to an h.323 service provider trough the internet via an IPIP GW. like this:

Callmanager -- ICT -- IPIPGW -- Internet -- h.323 SP

Due to obvious bandwidth issues, a I am using g.729 for the calls, and the calls complete just fine, but when using a service such as transfer (transfering a call to another ip phone), the call disconnects, not immediatly but after a couple of seconds, there is no audio and then disconnects.

I have an xcoder and software mtp registered to the callmanger and available to the devices.

Can anybody please point me in the right direction? Is this even possible?

any help will be appreciated

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m.batts Fri, 03/30/2007 - 03:44
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Just to check does the ICT have the MTP required box ticked?



jmthewissen Fri, 03/30/2007 - 11:28
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sure does.

I notice that the phone that receives the transfered call receives the call, first tries to use g.729, then changes to g.711 and finally disconnects.

jposada_us Thu, 07/19/2007 - 21:27
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jmthewissen, documentation say that it's possible when using H.323-IPIPGW-H.323 but I have not tried it yet. At this moment I have the same scenario but with the IPIPGW doing interworking from SIP to H.323 and found exactly the same thing you mentioned...

--when using a service such as transfer, hold, or conference the call disconnects, not immediately but after a couple of seconds, there is no audio and then disconnects--

Reading the documentation it says that those services are not sported for H.323 to SIP but they are for H.323 to H.323.

It should be a transcoding issue.

jposada_us Mon, 07/23/2007 - 11:56
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Hello jmthewissen, I have now solved the problem.

I have all the path using codec g.729r8 but needed to configure an MTP and Conference Bridge on the IPIPGW; conference, hold/resume, calltransfer and callforward are working ok.

Hope this can help you.

Best regrads.

jmthewissen Mon, 07/23/2007 - 12:05
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The problem we were facing was because the payloads were different on each of the call legs. As far as I know there is no way around that when using g.729.

I never tried using the conference bridge though, ist's worth a shot.

Will let you know.


jposada_us Mon, 07/23/2007 - 12:17
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So your problem is solved now?

I'm not sure if I'm underestanding you, when you say "there is no way around..." you mean that it's not posible?

I tell you there is... I have working those features with g.729, have to enable on the inbound and outbound faststart with g.729


jmthewissen Mon, 07/23/2007 - 12:35
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I am aware it is possible to make work, when you are using the same packetization period on all the call legs.

The thing here was that the service provider was using g729 with 50 miliseconds, and we were using g729 with 20 miliseconds. Supplementary services are not supported in this scenario.

With matching packetization periods, works like a charm.

mtcumtcu76 Sat, 12/15/2007 - 01:03
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hi jmthewissen,

could you post latest "show running config" of your router which running ipipgw software?


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