We have a PSTN termination provider for outbound calls, including faxes. They don’t act as a back-to-back user agent for faxes and just forward packets, which is causing issues on T.38 negotiation, and failures like this:
[Oct 30 07:42:59] WARNING[2087218][C-001e819c] udptl.c: UDPTL (SIP/peer1-00493eee): UDPTL asked to send 41 bytes of IFP when far end only prepared to accept 38 bytes; data loss will occur.You may need to override the T38FaxMaxDatagram value for this endpoint in the channel driver configuration.
The problem is that the different endpoints a call might go to might use different T.38 settings. We can’t use different T.38 settings in sip.conf entries, because from the point of view of our Asterisk server all calls go to the IP address of the PSTN termination provider, not the endpoint that the PSTN termination provider is forwarding the packets to.
Does anyone know of a solution to this? Is it possible to have our side adjust to whatever T.38 settings the endpoint wants to use?
Thanks in advance!