FoIP - SIP trunk & T.38

[Henry Britz]

We created a SIP trunk from our CUCM to a FAX server.

The FAX server requires T.38 and we created T.38 on a MGCP gateway.

The traffic arrives at the FAX server from the CUCM SIP trunk but nothing is received on the FAX server from the MGCP gateway.

How do we bind the SIP trunk to the MGCP gateway to initiate T.38 for the FAX server?

Can the CUCM convert a G711 fax to T.38 without a gateway, if so how?

Attach a .PNG file with the diagram

[Ayodeji Okanlawon]

Henry,

What is the region setting between the gateway and the sip trunk set to? From the trace it looks like it is set to G729. Your fax server wants to do either G711u or G711alaw..But CUCM cant do any of that codec, this is most likely due to region settings..Please check this and ensure that it is set to G711

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[Henry Britz]

The region is set to G711. If you look at the latest attach trace "0 PCMU/8000 a 0 PCMU/8000 a" means that we use G711. Where in the trace do you still see G729.

Thank you

Regards

Henry

[Ayodeji Okanlawon]

That is what your fax server is advertising. That is the 200 OK from your fax server. CUCM needs to send an ACK to that 200 ok and the codec used will depend on the region between the gateway and the sip trunk to the fax server. Can you send the full cucm traces?

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[Henry Britz]

I will ask the customer for the traces and will forward them to you ASAP. That will most likely be later tonight or tomorrow.

Thank you

Regards

Henry

[Jean-Christophe Majchrzak]

"0 PCMU/8000 a 0 PCMU/8000 a" is what your fax server asks to CUCM, which is unable to do so because the Region is not allowed to use G711.

If you have configured this setting into the Region have you reset the SIP Trunk to apply changes ?

[Henry Britz]

We will setup a test environment tomorrow. We will configure it separately from the life environment and then run the test. Will update as soon as the tests are finish.

Thank you all for the assistance so far.

Regards

Henry

[Jagpreet Singh]

Henry,

As Aok said, we need the complete CCM traces to move forward on this.

Regards,

Jagpreet


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