[asterisk-users] T.38 Peer Negotiation Fails

Chris Miller
2010-06-29T06:04:11Z

Asterisk 1.4.32 (Also 1.4.26, 1.4.33)
Broadvox ITSP   (xxx.xxx.xxx.xxx)
Linksys 2102    (yyy.yyy.yyy.yyy)

Both peers :
canreinvite=yes
t38pt_udptl = yes

I'm having some trouble getting a T.38 fax call established with
Broadvox. During negotiation, Asterisk sends a SIP re-invite (T38
switchover) to Broadvox with the Asterisk server's IP address in the
Connection Information (c) instead of the Linksys ATA's IP address.
This causes the negotiation to revert back to t38state zero
(chan_sip.c: T38_DISABLED), and shortly after the ATA hangs up.

What is a bit odd about this, is that Asterisk says it's about to
establish a peer to peer UDPTL connection :

chan_sip.c: Sending reinvite on SIP
'1057817983_43059159 at xxx.xxx.xxx.xxx' - It's UDPTL soon
redirected
to IP yyy.yyy.yyy.yyy:16468

chan_sip.c: Strict routing enforced for session
1057817983_43059159 at xxx.xxx.xxx.xxx

On a known good/working T.38 configured Asterisk PBX elsewhere (with
Affinity as the ITSP), I also see the "Strict routing" message, yet
T.38 negotiation achieves t38state 5 (chan_sip.c: T38_ENABLED) and
calls are successful.

I've been comparing Asterisk debug from both systems as well as
wireshark captures, but I can't figure out why Asterisk is not
sending the Linksys ATA's IP address.

Broadvox uses a Sonus switch and gateway with separate IP addresses
for SIP and media. Affinity uses "Sippy" (?) with a common IP for
SIP and media.

I believe I've already covered all the possible configuration
scenarios. I just can't get the right detail out of Asterisk to
determine if this is an Asterisk issue, or an ITSP issue.

Using bug ID#16705 as a guide, I patched this version, as well as
downgraded to a known working version, and to the latest 1.4.33.1
which includes several t.38 fixes.

https://issues.asterisk.org/view.php?id=16705

Thoughts?

Chris