[Freeswitch-users] Problems with FAX transmission

Jan Riedinger riedinger at sns.eu
Fri Sep 17 09:50:52 PDT 2010

  Hello All Together,

I tried to set t38_passthru=true in the dialplan, but fax transmission 
is still not working. Now INVITE SDP (t38) is passed through, but e. g.  
the response  200 OK SDP (t38) is  not passed.

Just one hint, if you compare "Fax trace2.tif" with the trace of my last 
e-mail: I'm not sure, if I made both traces with exactly the same setup, 
because I tested with various carriers, but I observe similiar behaviour 
with all of them.

Another hint was to set <action application="set" 
data="proxy_media=true"/>. In the Wiki I found "Proxy media is really a 
special hack that should only be used for T.38 passthrough. If you are 
using it for other purposes, think about it some more...". Do you think 
it is reasonable to use this setting for a common purpose wholesale switch?

Thank you in advance

Am 17.09.2010 15:56, schrieb Brian West:
> You need to setup t38_passthru=true, I'm currently working on an issue where it seems to not be forwarding the invite properly.
> /b
> On Sep 17, 2010, at 10:21 AM, Meftah Tayeb wrote:
>> hi,
>> <action application="set" data="bypass_media=true"/>  if you are in lan,
>> or<action application="set" data="proxy_media=true"/>  to proxy the
>> media from A-Leg to B-Leg
>> Jan Riedinger a écrit :
>>> I'm trying to send a fax via our Freeswitch switch without success.
>>> It seems that the "invite sdp (t38)" message isn't forwarded from the
>>> gateway of the fax receiver to the gateway of the fax sender. See the
>>> attached tif file with the Wireshark trace.
>>> If I try the fax transmission with the same setup with a commercial
>>> softswitch (same fax equipment, same sending and receiving gateways),
>>> the fax transmission is successful.
>>> We are using the following settings in the sip_profile
>>> <param name="inbound-codec-negotiation" value="greedy"/>
>>> <param name="inbound-late-negotiation" value="false"/>
>>> Does anybody know what's going wrong?
>>> Thank you in advance
>>>       Jan Riedinger
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Jan Riedinger                           Phone :  +49-30-39 73 19 66
Dipl.-Inf. | Managing Director          Fax   :  +49-30-39 73 19 64
                                         E-Mail:  riedinger at sns.eu
SNS Consult GmbH                        ICQ   :  163-237-041
Südwestkorso 49a                        MSN   :  jan at sns-consult.de
14197 Berlin GERMANY                    Skype :  Jan Riedinger

AG Charlottenburg - HRB 71973

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