[asterisk-users] T.38 Fax With Flowroute SIP Provider

[Ryan Wagoner]

Does anybody have T.38 faxing working with Flowroute? I am running
Asterisk 1.6.2.7-rc3 with spandsp 0.0.6-pre17. I can successfully
receive faxes over ulaw. I enabled T.38 with t38pt_udptl=yes in
sip.conf. When I receive a fax it tries to negotiate T.38 and
Flowroute sends back a Bad Request response saying I have a SIP syntax
error.

Flowroute support is recommending that I try again after removing
externip and localnet from sip.conf. They state that their service
will recognize the private IP and rewrite the SIP packets. However
this is going to cause issues for my remote SIP phones.

Thanks,
Ryan

DEBUG[32389] app_fax.c: Negotiating T.38 for receive on SIP/flowroute-00000000

INVITE sip:+number at xx.xx.xx.xx:5060 SIP/2.0
...
CSeq: 102 INVITE
User-Agent: Asterisk PBX 1.6.2.7-rc3
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO
Supported: replaces, timer
X-asterisk-Info: SIP re-invite (External RTP bridge)
Content-Type: application/sdp
Content-Length: 293

v=0
o=root 2048302926 2048302927 IN IP4 xx.xx.xx.xx
s=Asterisk PBX 1.6.2.7-rc3
c=IN IP4 xx.xx.xx.xx
t=0 0
m=image 4575 udptl t38
a=T38FaxVersion:0
a=T38MaxBitRate:14400
a=T38FaxFillBitRemoval
a=T38FaxRateManagement:transferredTCF
a=T38FaxMaxDatagram:1400
a=T38FaxUdpEC:t38UDPFEC

SIP/2.0 400 Bad Request
...
CSeq: 102 INVITE
Error-Info: <sip:+number at xx.xx.xx.xx>;cause="[line 023] SIP syntax error"
Content-Length: 0

WARNING[32389] app_fax.c: Transmission error