17 Feb
2005
17 Feb
'05
11:07 p.m.
How is the fax generated? A PSTN fax machine connected
to asterisk?
span_dsp?
A PSTN fax machine comes in to the Asterisk (via SIP or IAX. tested both
ways but neither works), where the caller gets authenticated (via ANI or
DTMF) and the destination leg of the call is originated by Asterisk to
Level-3 via SER...
-----Original Message-----
From: Klaus Darilion [mailto:klaus.mailinglists@pernau.at]
Sent: Thursday, February 17, 2005 9:46 AM
To: scm-j(a)nuntius.com
Cc: serusers(a)lists.iptel.org
Subject: Re: [Serusers] Fax problem with SER/Asterisk
scm-j(a)nuntius.com wrote:
I am facing some problems with sending fax calls. I am
using G.711
codec. However, my service provider (Level-3) does not support T.38
fax
relay.
According to Level-3 they think the problem lies in the Media
Description field of the SDP message I am sending them. The problem
is
related to the Media Format sub-field (value 101)
that I am
sending,
which according to them should be removed.
The SDP Media Description field I am sending, looks as follows:
m=audio 20744 RTP/AVP 0 101
which is decoded by Ethereal as follows:
Media Type: audio
Media Port: 20744
Media Proto: RTP/AVP
Media Format: ITU-T G.711 PCMU
Media Format: 101
My call is initiated by Asterisk which is sent to Level-3 via SER
Asterisk -à SER -à Level-3
The SIP call flow looks fine for the call. The sending fax sends the
page and then gives an error. The receiving side gives me an error and
prints a blank page.
My questions are as follows:
1) Could the Media Format 101 be the problem? If so, how do I
remove the 101? This change is probably in Asterisk, as it initiates
the
call, and not SER, or probably both.
I don't think that this will cause problem. If this is really the
problem, than the L3 gateway su$%s.
2) If not, should I be looking elsewhere in SER/Asterisk to
solve
this problem?
How is the fax generated? A PSTN
fax machine connected to asterisk?
span_dsp?
regards,
klaus