T.38 protocol faxing to Fongo Mobile no longer works

[Liptonbrisk]

I have alerted Fongo about this. They may not care or may be very busy dealing with support tickets. No one responded yet.

Anyway, https://support.fongo.com/hc/en-us/arti ... ngo-Mobile no longer applies when Fongo Mobile's voicemail system answers the incoming T.38 fax protocol call. The call eventually drops after reaching Fongo Mobile's voicemail system. This behaviour changed after the outage.

Incoming, regular G.711 codec fax calls to Fongo Mobile work.


All incoming fax calls work, including ones sent using T.38 fax protocol, when reaching Freephoneline's voicemail system. Negotiation always works.

I am unable to see what's going on after the call is answered by Fongo Mobile's voicemail system in my syslog.

Eventually, I just see this:

[T38] event callback, id: 1, p1: 0, p2: 3295800

[locallanIP]<7> FXS[1]:FAX T38 event - disconnected

[locallanIP]<7> sendto a3d56f24:5060

[locallanIP]<7> BYE


This situation is strange, considering the switch (PortaSIP) appears configured to accept T.38 for Freephoneline's voicemail system but not for Fongo Mobile.
https://docs.portaone.com/docs/mr106-fa ... ted-codecs

T.38 works even when T.38 ECM is enabled when connecting to Freephoneline's voicemail system too, which is good.