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

[Tihomir Culjaga]

well, my experience with T.38 is that we switched it off within our network
and now use passthrough instead :P.

the reason:

   - new fax machines that defaults to v.34 and on some you cannot disable
   SG3 at all... just imagine what pain it is to produce a how to disable V.34
   manual for every damn fax machine
   - a variety of T.30 <> T.38 mapping issues, broken GWs/ATAs that don't do
   a correct encoding/decoding expectantly when it comes to a terminating fax
   server that doesn't send a proper EOP... God save our souls...
   - our network has very low jitter - up to 40 ms , so passthrough works
   perfect
   - bandwidth become cheap :=)
   - and ... don't even remember any fax issues after shutdown T.38

i could go with the list... but i suppose you have better things to do  :P


T.

On Thu, Oct 22, 2009 at 9:29 PM, Gabriel Kuri <gkuri at ieee.org> wrote:

> 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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