Modem call fails on SIP, ITSP proposes T.38, Not accepted

[Tom Ribbens]

Hi all,

We are encountering a problem with a modem connection that does not work. Attached is a debug ccsip messages made on the cube.

Call-ID betweer CUBE and CUCM: 8b3fec80-c714746-36530-b08a8c0@192.168.8.11

Call-ID to ITSP:628C1A40-42D811E2-91EFAF74-6CC424DD@10.218.16.3

We see that we send an INVITE to the ITSP requesting G.711a, but we get an INVITE back for T.38, which we cannot accept since this is not a fax connection. ITSP says they send another INVITE again for G.711, but I do not see that invite in our logs. I do see we send multiple BYE messages that do not get a response, before finally sending a BYE that gets a response.

Is it possible that this is a configuration error on our end? It has worked, so we believe it to be a ITSP issue, they say they are investigating, but they think it's not their fault.

Thanks

[Tom Ribbens]

Finally gotten round to testing with a second modem that is installed. This one works as expected.

In the INVITE to the ITSP, the only difference is that the working modem does not include this in the SDP:

a=rtpmap:100 X-NSE/8000
a=fmtp:100 192-194

The difference on CUCM is that the working modem is connected to a ATA 186, while the non-working modem is connected to a VG248.

Is there a way to disable NSE on that VG248 port?