[Freeswitch-users] Proxy media mode with T.38 re-invite

[Peder]

We have probably 30-40 fax machines running T.38 between Linksys SPA-3102
and Cisco gateways.  We have a pretty good success rate and we have been
doing this for probably 2-3 years.  We have a couple of them going thru an *
1.4 box and it seems to work ok.  One of my projects is to try and get them
all converted to go thru an FS box, I just haven't had time.  Our biggest
issues have always been error correction.  Once we disable that on the fax
machine, it seems to work pretty good.  As a general rule, we have found
that older cheaper machines work better.  New fancy machines are unreliable
and that could certainly be related to v.34 issues, but we haven't bothered
to get that into it to find out.

Peder

-----Original Message-----
From: freeswitch-users-bounces at lists.freeswitch.org
[mailto:freeswitch-users-bounces at lists.freeswitch.org] On Behalf Of Gabriel
Kuri
Sent: Thursday, October 22, 2009 2:29 PM
To: freeswitch-users at lists.freeswitch.org
Subject: Re: [Freeswitch-users] Proxy media mode with T.38 re-invite

AFAIK T.38 v2 supports a max speed of 14.4 anyhow, so that's the max
speed you'll ever see in the SDP. T.38 v3 supposedly supports v.34
speeds, however no one that I've seen has implemented it yet - not sure
it's even an official standard?

Yes, in my experience, v.34 capable FAXes do not properly negotiate down
to 14.4 speeds, we've always had to disable v.34 (or whatever the option
is called on your particular make/model to force it down to 14.4 or
slower speeds). We use the Cisco/Linksys ATAs - I've heard there's
better ATAs out there that properly negotiate the FAX down to 14.4 on
the T.30 side of the connection, but never had a chance to play with them.

I'd certainly be interested to hear anyone's experience with T.38
reliability and various combinations of FAX machines and make/model of ATAs.

Gabe

Kristian Kielhofner wrote:
> Gabe,
> 
>   I don't think any of them are plus the T.38 SDP tells me the bitrate
> is 14400, certainly not V.34 speed.
> 
>   Are you saying the machine even trying to negotiate V.34 poses a
problem?
> 
> On Thu, Oct 22, 2009 at 2:16 PM, Gabriel Kuri <gkuri at ieee.org> wrote:
>> Out of curiosity, is it a Super G3 (ie v.34) capable FAX? We've had
>> nothing but intermittent problems with Super G3 FAXes over T.38, unless
>> v.34 is strictly turned off on the machine.
>>
>> Gabe
>>
> 


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