[asterisk-ss7] T38 fax issue

[Gregory Massel]

See https://wiki.asterisk.org/wiki/display/AST/T.38+Fax+Gateway

Particularly the line:

exten => 1,n,Set(FAXOPT(gateway)=yes)

which you need on the SIP side of the DAHDI-SIP bridge

On 2014/08/26 08:01 AM, Huseyin Kaya wrote:
> Hello
>
> Does anyone has a working libb7 server that able to handle T38 faxing.
>
> I am working on this for the last 10 days. But still no solution.
>
> I am receiving the call from sip and sending to telco with ss7.
>
> At the beginning of the call everything is fine ( i mean codec 
> negotiation) . Then the remote sip side detects the fax tone that 
> remote end sends and Then the sip remote side sends the t38 invite and 
> asterisk sends SIP 200 OK message with G711 and G729 codec in SDP.
>
> My customer is saying that if i am sending SIP 200 OK to his T38 
> invite .in SDP of SIP 200 OK there should be only T38.
>
> Also disabling t38 with t38pt_udptl=no didnt change anything.  Still 
> asterisk is sending SIP 200 OK message with G711 and G729 codec in SDP 
> as reply to T38 invite.
>
>
> I will be glad if current libss7 users can advice me a way to find a 
> solution on this issue
>
> Regards
>
> ------------------------------------------------------------------------
> *From:* Huseyin Kaya <huseyinkaya at yahoo.com>
> *To:* Kaloyan Kovachev <kkovachev at varna.net>; 
> "asterisk-ss7 at lists.digium.com" <asterisk-ss7 at lists.digium.com>
> *Sent:* Friday, August 22, 2014 5:32 PM
> *Subject:* Re: [asterisk-ss7] T38 fax issue
>
> Hello
> Actually it will be fine If I can send sip 488 not acceptable here to 
> the re invite of t38 .
> But Asterisk is sending sip 200 ok with voice codecs in SDP.
> So if i was able to send sip 488 . The fax will contunie with g711
> Setting faxopt(gateway)=yes and t38pt_udptl = 
> yes,redundancy,maxdatagram=400 didnt work.
> By setting these asterisk should send sip 200 with SDP T38 but it is 
> still sending speech codec(g11u,etc..) in SIP 200 sdp.
> Also disabling t38 with t38pt_udptl=no didnt change anything.
>
> Regards
>
>
> ------------------------------------------------------------------------
> *From: * Kaloyan Kovachev <kkovachev at varna.net>;
> *To: * Huseyin Kaya <huseyinkaya at yahoo.com>; 
> <asterisk-ss7 at lists.digium.com>;
> *Subject: * Re: [asterisk-ss7] T38 fax issue
> *Sent: * Fri, Aug 22, 2014 1:52:44 PM
>
> Hi,
> in addition to FAXOPT(gateway) you may try to request transmission
> medium from telco - see SS7_TMR or SS7_TMR_NUM, as it should be set on
> the outgoing (dahdi) channel you need to set it on the SIP channel with
> underscore (_SS7_TMR)
>
> The possible options are defined in libss7.h and SS7_TMR_3K1_AUDIO (or 3
> as num) works fine here. If you can detect the fax calls you may request
> 64K_UNRESTRICTED data for them
>
> On 2014-08-22 15:47, Huseyin Kaya wrote:
>
> > Hello
> >
> > I am using Sangoma A104DE with libss7 on Asterisk 11.5.0 and
> > terminating calls to telco with ss7 . We are using patched version of
> > Libss7 that have timers
> > functionality.(https://issues.asterisk.org/jira/browse/SS7-27)
> >
> > The server is on production for the last 6 months and everything was
> > fine
> >
> > My interconnection with telco is only one way. From sip to ss7 .
> >
> > Everything is fine except one thing.
> >
> > One of my customers asked for t38 faxing. then i found myself in
> > trouble.
> >
> > I get several sip traces and found the problem at the end .When i
> > receive an invite T38 , asterisk is sending 200 OK message but in SDP
> > it is sending g711u,g711a,g729 as codecs. So after this point
> > everything is messed up.
> >
> > I tried to set t38pt_udptl=no in sip.conf , but still asterisk is
> > sending sip 200 ok with sdp g711...
> >
> > ? tried to set t38pt_udptl = yes,redundancy,maxdatagram=400 and
> > setvar=FAXOPT(gateway)=yes,20 in sip.conf but still i couldn't manage
> > to receive fax
> >
> > So basically what i need to send fax from sip to telco but could not
> > manage to do till now.
> >
> > Everything except fax is working like a charm.
> >
> > Is anyone succeed to handle fax with libss7.
> >
> > I will be glad if an expert can show me a way to achive this.
> >
> > Best Regards
>
>
>
>
>

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