[Serusers] Fax problem with SER/Asterisk

[Vitaly Nikolaev]

Hello.

 

I am working with level3 also... They require inbadn DTMF and you are trying
to use rfc2833..

 

U have to change config of the whatever SIP UA you use from your side and
configure it to use G711/inband DTMF

 

 

  _____  

From: serusers-bounces at iptel.org [mailto:serusers-bounces at lists.iptel.org] On
Behalf Of scm-j at nuntius.com
Sent: Thursday, February 17, 2005 12:33 PM
To: serusers at lists.iptel.org
Subject: [Serusers] Fax problem with SER/Asterisk

 

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 ---> SER ---> 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.

2)       If not, should I be looking elsewhere in SER/Asterisk to solve this
problem?

 

 

regards,

SCM

 

 

 

 

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