[Freeswitch-users] Faxing problems if B leg offers T.38

[Yehavi Bourvine]

It might be related to JIRA 3274 which I've (re)opened recently.
When Freeswitch receives a RE-Invite with T.38 parameters inside it responds
with "Trying" but no "OK" following it. The originator then times out and
disconnects the call.

                     Regards, __Yehavi:

2011/5/24 Rob Morin <rmorin at blie-ent.com>

> David,
>
>
>
> It isn’t the ATA. I’ve tried both the Grandstream HandyTone 502 and
> Cisco/Linksys SPA 2102. Same story in both cases.
>
>
>
> I had my carrier help me troubleshoot and we can see the SIP request from
> the carrier come in. When T.38 is enabled, it is forwarded to the A leg, but
> the response from the A leg isn’t forwarded back to the B leg. I can produce
> traces that show this.
>
>
>
> When T.38 isn’t enabled, the B leg is sending a T.38 reinvite. FS doesn’t
> respond or forward it. So the connection dies.  I have every reason to
> believe that I’d be able to send the fax if FS would respond with a 488
> indicating T.38 is not acceptable. But instead, all I get is silence. Again,
> I can produce traces that demonstrate this.
>
>
>
> There’s another similar email  trail out there,
> http://freeswitch-users.2379917.n2.nabble.com/T-38-via-UPDATE-request-td3821994.html,
> but I’m not certain that they’re related.
>
>
>
> Thank you for your help!
> Rob
>
>
>
> *From:* David Ponzone [mailto:david.ponzone at ipeva.fr]
> *Sent:* Monday, May 23, 2011 6:11 PM
> *To:* FreeSWITCH Users Help
> *Subject:* Re: [Freeswitch-users] Faxing problems if B leg offers T.38
>
>
>
> Rob,
>
>
>
> perhaps you should not consider T38 is 100% interoperable.
>
> You may tell us what ATA is that, because some of them are nice piece of
> junk.
>
>
>
> David Ponzone  Direction Technique
>
> email: david.ponzone at ipeva.fr
>
> tel:      01 74 03 18 97
>
> gsm:   06 66 98 76 34
>
>
>
> Service Client IPeva
>
> tel:      0811 46 26 26
>
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>
>
>
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> * *
>
>
>
>
>
> Le 23/05/2011 à 20:51, Rob Morin a écrit :
>
>
>
> I’m having problems faxing if the B leg offers T.38.  Several scenarios,
> but always the same result.
>
>
>
> First, the architecture
>
>
>
> FAX à ATA (T.38 optional) à FS à Carrier  à Destination (Possibly another
> carrier (PSTN) and the fax machine)
>
>
>
> On my ATA, T.38 is enabled (Auto Detect).
>
>
>
> If the destination supports T.38, the Carrier will offer it to Freeswitch.
> If the Destination doesn’t support T.38, the B leg doesn’t offer it and the
> faxes go through.
>
>
>
> I’ve set Freeswitch as:
>
>       <action application="set" data="fax_enable_t38=true"/>
>
>       <action application="export" data="t38_passthru=true"/>
>
> When that’s the case, and the B leg offers T.38, Freeswitch passes through
> the offer and the ATA responds, 3 times. But the response never gets sent to
> the B leg, so it terminates the call after about 30 seconds.
>
>
>
> When I set Freeswitch as:
>
>       <action application="set" data="fax_enable_t38=false"/>
>
> The B leg still offers T.38 if its other side is capable. Freeswitch
> doesn’t pass the offer through and the B leg terminates the call after about
> 30 seconds.
>
>
>
> I’m running on a recent git ( FreeSWITCH Version 1.0.head (git-86d757d
> 2011-05-17 22-51-47 -0500) ).
>
>
>
> I’ve had no success attempting to configure FS as a gateway. Frankly, T.38
> “passthrough” has had the most success, mostly when the other ends aren’t
> T.38 capable and it stays in G711u.
>
>
>
> Is there something else I need to do to enable T.38 in passthrough mode?
>
>
>
> Thank you,
> Rob Morin
>
>
>
> PS – I can provide tcpdumps of this, or whatever else is necessary.
>
>
>
>
>
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