[Freeswitch-users] Fax T.38 reinvite drops most of the SDP

[Peter Steinbach]

Hallo,

we have the following fax scenario:

Asterisk(SIP provider) => Freeswitch => Auerswald COMmander 6000R PBX
IPS 10.10.10.10                => 20.20.20.20 => 30.30.30.30

Fax is initiated by Asterisk with PCMA codec
Auerswald connects with PCMA and then does a T.38 reinvite

In the T.38 reinvite Auserwald PBX sends a
     m=audio 0 RTP/AVP 19
     m=image 49376 udptl t38.

Freeswitch then finally drops most of the SDP and answers with
   m=image 0 udptl t38.
   m=image 0 udptl t38.

and Auerwald PBX hangs up

Anybody has an idea what is causing this? Why is Freeswitch not
forwarding the complete SDP message. Maybe the "m=audio 0" is causing
the problem?




Dialplan is just
  sip_copy_multipart=false
  and bridge

In internal and external profile
   <param name="t38-passthru" value="true"/>
is set.

Freeswitch log shows in between:
2014-02-10 13:23:10.869112 [INFO] sofia.c:5543 Activating T38 Passthru

========= Here are the SDPs==================
SDP from Reinvite Auerswald to Freeswitch
v=0.
o=- 5045970593938686503 4940450077875186463 IN IP4 30.30.30.30.
s=-.
c=IN IP4 30.30.30.30.
t=0 0.
m=audio 0 RTP/AVP 19.
m=image 49376 udptl t38.
a=T38FaxVersion:0.
a=T38MaxBitRate:14400.
a=T38FaxUdpEC:t38UDPRedundancy.
a=T38FaxUdpEC:t38UDPFEC.
a=T38FaxRateManagement:transferredTCF.
a=T38FaxMaxDatagram:512.
a=T38FaxMaxBuffer:1472.


SDP from Invite Freeswich to Asterisk:
v=0.
o=FreeSWITCH 1392015640 1392015642 IN IP4 20.20.20.20.
s=FreeSWITCH.
c=IN IP4 20.20.20.20.
t=0 0.
m=image 19342 udptl t38.
a=T38FaxVersion:0.
a=T38MaxBitRate:14400.
a=T38FaxRateManagement:transferredTCF.
a=T38FaxMaxBuffer:1472.
a=T38FaxMaxDatagram:512.
a=T38FaxUdpEC:t38UDPFEC.

SDP from Ok from Asterisk to Freeswitch:
v=0.
o=root 1238355194 1238355195 IN IP4 10.10.10.10.
s=Asterisk PBX 11.0.1.
c=IN IP4 10.10.10.10.
t=0 0.
m=image 4609 udptl t38.
a=T38FaxVersion:0.
a=T38MaxBitRate:14400.
a=T38FaxRateManagement:transferredTCF.
a=T38FaxMaxDatagram:702.
a=T38FaxUdpEC:t38UDPFEC.


SDP from 200 OK from Freeswitch to Auerswald:
v=0.
o=FreeSWITCH 1392020936 1392020938 IN IP4 20.20.20.20.
s=FreeSWITCH.
c=IN IP4 20.20.20.20.
t=0 0.
m=image 0 udptl t38.
m=image 0 udptl t38.


Auerswald sends a BYE with Reason: SIP;cause=488;text="Not Acceptable
Here".



-- 
With kind regards
Peter Steinbach 

Telefaks Services GmbH
mailto:lists (att) telefaks.de
Internet: www.telefaks.de