• The caller, a local fax machine (Fax, ATA and Freeswitch) with T.38, is behind a slow line so therefore T.38 is needed here
• a central Freeswitch fax server serves as a central gateway to the SIP provider
• the SIP provider sometimes reinvites T.38 and sometimes not.
• In case, the SIP provider does NOT answer with T.38, the central Freeswitch fax server shall act as a T.38 gateway and transcode between local fax (T.38) and SIP provider (T.30)
• In case, the SIP provider does answer with T.38, the central Freeswitch fax server shall pass T.38 to the local fax ,machine (T.38)

How we set this up

• according to the wiki we have a dialplan as follows: (this is what CLI shows)
  

Dialplan: sofia/internalvpn2/49274xxxxx@10.7.0.1 Action set(fax_enable_t38=true)
Dialplan: sofia/internalvpn2/49274xxxxx@10.7.0.1 Action set(fax_enable_t38_request=true)
Dialplan: sofia/internalvpn2/49274xxxxx@10.7.0.1 Action set(execute_on_answer=t38_gateway self)
Dialplan: sofia/internalvpn2/49274xxxxx@10.7.0.1 Action ring_ready()
Dialplan: sofia/internalvpn2/49274xxxxx@10.7.0.1 Action bridge(sofia/gateway/sip.provider.com/xxxxxxxxxxxxxxx@sip.provider.com)

In all profiles, we have
<param name="t38-passthru" value="true"/>

In case, the SIP provider does NOT answer with T.38, it works. The caller's side is reinvited with T.38, the SIP provider side is T.30

What the problem is: When the SIP provider' side IS answering with T.38, then (sometimes, when I send it via cli from the local freeswitch near the sending fax machine, it works)

• caller initiates a call
• call is bridged to the SIP provider' side
• we receive a T.38 Reinvite from the SIP provider' side
• Freeswitch sends Trying back to the the SIP provider' side
• Freeswitch logs: set(execute_on_answer=t38_gateway self)
  
• Freeswitch sends a T.38 Reinvite to the caller, establishes T.38 on this side.
• But the T.38 Reinvite from the SIP provider' side is not answerered
• So the SIP provider' sidehangs up after 10 sec of timeout.

What are we doing wrong here? Is it possible to act as a t.38 passthrough router and a T.38 gateway in the same dialplan?

-- 
With kind regards
Peter Steinbach 

Telefaks Services GmbH
mailto:lists (att) telefaks.de
Internet: www.telefaks.de