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@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@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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