CUCM 7.1 G.729 SIP Trunk to Nortel

Unanswered Question
Jul 27th, 2009
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Hi All,

I have created a SIP trunk from CUCM ver 7.1 towards a Nortel PBX ver 5.0.

The scenario is like:

Phone A----->CUCM 7.1-----SIP Trunk--->Nortel CS 5.0-------> Phone B

The regions are configured to be in G.729. As per the interop document we have to check MTP required check box so as to support the SIP Early Media Offer.

I have configured a transcoder, to have the MTP requirement. I have ensured that transcoding is invoked in all the calls.

When calls are made from Phone A connected to CUCM to Phone B connected to Nortel, some supplementary features are not working.

If Phone A calls Phone B, and Phone A presses HOLD and RESUME, it works fine at the Cisco end. But at the same time, when Phone B presses HOLD and RESUME, Phone B is able to hear Phone A but Phone A is not able to hear Phone B.

The strange thing is , after the previuos HOLD retreival failure for Phone B, If I press HOLD and RESUME at the Phone A the voice path is re-established.

Any idea of this strange behaviour?



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Overall Rating: 3 (1 ratings)
gogasca Tue, 07/28/2009 - 08:13
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Hi Manu,

Make sure that MTP invoked is an MTP not a transcoder.

You need to use SW MTP in the IOS router, because there's a limitation DSP firmware for transcoding which we cannot do G729-G729. It must be an MTP configured to do G729.

Let us know if that helps.

manumohan200 Tue, 07/28/2009 - 08:52
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Hi Gonzalo,

Thanks for the reply. Infact I had tried this initially but couldn't make success. I had ensured the G.729 codecs are specifid under the dspfarm profile. But somehow the calls were not going.

After this I configured the present scenario of transcoder after which only the calls are going.

Any other thoughts in this?



gogasca Tue, 07/28/2009 - 09:45
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for SW MTP in IOS router we dont really use DSPs. thats the trick Pure SW IOS MTP.

You can upload CUCM detailed traces and let us know the configuration so we can take a look, if urgent dont hesitate to open a TAC case with us.

Thank sManu

manumohan200 Tue, 07/28/2009 - 09:48
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Thanks Gonzalo,

Let me check my region configurations b'cos I suspect something here, and reproduce the issue. Thanks once again.



sshams007 Tue, 07/28/2009 - 11:07
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Hi Manu,

I am also running into a similar issue but im using H.323 and not SIP. Iv'e already raised a TAC case but and TAc asked me to use IOS software MTP to be configured and tested, but no use :(

PLease share with me the procedure should you get the issue resolved. Thanks in advance


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