[asterisk-users] T.38 with Audiocodes gateway

Olivier oza.4h07 at gmail.com
Fri Apr 29 01:34:11 CDT 2016


I'm helping a colleague (*) which has the following setup:

ITSP --- <T.38 capable PJSIP trunk> --- Asterisk 13 ---  <PJSIP>--
Audiocodes MP-112 ---  <FXO/FXS> --- Fax machine

My issue is the following :
Audiocodes gateway reject INVITEs with 488 Not Acceptable Here

It seems this gateway requires t38 settings to be present in SDP body in
the very first INVITE.

My questions are the following:

1. I expected T.38 to exclusively work with reINVITE where calls are
established as normal voice calls (PCMA/PCMU in SDP, for instance) and then
upgraded to T.38 (when CNG is detected, for instance).
Have you ever heard of T.38 sessions being established right from the start
(ie with T.38 settings in the first INVITE) ?

2. Is it possible to configure Asterisk to pass T.38 settings in SDP in the
first INVITE it sends ?

3. Any suggestion with Audiocodes gateway ?


(*) That's the reason why I don't have as many details as I would like, at
the moment.
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