On 07/18/2012 09:43 PM, Matthew Jordan wrote:
----- Original Message -----
From: "Alejandro Recarey" <a...@recarey.org>
To: "Asterisk Users Mailing List" <asterisk-users@lists.digium.com>
Sent: Wednesday, July 18, 2012 6:30:26 AM
Subject: [asterisk-users] Using Asterisk 10.6 as a T38 Fax gateway
Hi all, and thanks for taking the time to read this.
I am trying to configure Asterisk 10.6 as a T38 Fax gateway. I am
receiving calls through the PSTN and want to send them to my VoIP
carriers as T38. This is my dialplan:
[fax]
exten => _X.,1,Set(FAXOPT(t38gateway)=yes,20)
exten => _X.,n,Dial(SIP/${EXTEN}@x.x.x.x)
The correct setting is not FAXOPT(t38gateway) - that is not a valid parameter
to pass to the FAXOPT function. As you mention below, the correct setting
is Set(FAXOPT(gateway)=yes). The optional timeout is fine.
https://wiki.asterisk.org/wiki/display/AST/Asterisk+10+Function_FAXOPT
I have tried with both FAXOPT(t38gateway) and FAXOPT(gateway). I have
also tried setting t38pt_udptl = yes,redundancy in sip.conf. None of
these things work. When we send a fax:
1. Asterisk does NOT send a REINVITE with the t38 offered. Reading
the
documentation, it should detect the fax tone with the audiohook and
then send a REINVITE with t38 capability.
Have you confirmed that Asterisk does not send the re-INVITE using either
a packet sniffer or by monitoring the log with 'sip set debug on'? Without
seeing the SIP message traffic and a DEBUG log, its hard to say what
might be the cause of your issues.
Typically, I would expect to see something like the following in a DEBUG log:
[Jul 18 08:29:18] DEBUG[20234] res_fax.c: detected v21 preamble from
SIP/ast1-g711-00000001
[Jul 18 08:29:18] DEBUG[20234] res_fax.c: requesting T.38 for gateway session
for SIP/ast1-t38-00000000
Note that this also answers your question in a subsequent e-mail: you
should be using res_fax, with either res_fax_spandsp or Fax for Asterisk.
2. Asterisk does not offer t38 in the SDP of the initial INVITE. This
is not a problem if it correctly detects and REINVITES for faxes, but
our destination carriers tell us that they cannot do the REINVITE
themselves because we do not offer t38 in our SDP, so they believe we
do not have that capability.
Obviously I would prefer to just detect the fax myself and have
asterisk do the REINVITE.
I have read all of the documentation on the asterisk wiki (which is
rather short) and anything else I could find online. Unfortunately
most of it is out of date and refers to asterisk versions 1.4 to 1.8,
which do not have T38 Gateway capability.
There typically isn't a lot of configuration that is needed for T.38
gateway support. The necessary dialplan configuration is documented
here:
https://wiki.asterisk.org/wiki/display/AST/T.38+Fax+Gateway
One thing that page doesn't mention is only spandsp supports T.38
gateway right now. The Digium FAX module does not.
Regards,
Steve
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