scm-j@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:
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.
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