CUCM 12.5.1.14900-63 SIP calls disconnect after 15 mins; refresh adj

[jonscmc]

I have a CUCM 12.5 installation where PSTN calls (through a Spectrum Enterprise SIP trunk) disconnect after 15 minutes. The CUCM connects directly to the telco-provided Audiocodes Mediant SBC. I do not have a CUBE involved in this setup.

Attached is a call trace. It appears the Spectrum SBC is sending a reinvite at the 15 minute mark and CUCM is responding “trying” but then perhaps never closes the loop? Then the SBC sends a 408 Request Timeout and tears the call down.

I have messed with the SIP refresh timeout in CUCM service parameters both increasing and decreasing it and the problem remains. I am not an expert but to me there must be some setting that can instruct CUCM to send something more definitive in response to a mid-session reinvite than “trying.”

Any ideas where to look?

Many thanks in advance.

[eyalraba]

I checked couple of calls in the logs, and I noticed that the MRA device side, puts the other party on hold, also you have the MTP option checked on the trunk.

Does the issue happen if:

- MTP not checked

- The other party does not put the call on hold

[eyalraba]

Also CUCM software MTP does not support T.38, and could cause some unexpected behavior, can you disable this codec from Audiocodes Mediant SBC side?