> The folks that devloped the fax V.protocols took into acount typical > copper problems like noise or echo. But what they never conceived of as > even being possible is that a call might shift around in the time > domain. Thanks to jitter/latency, the delay time of a call can change in > the middle of the call. That isn't possible with copper technologies. > This makes faxing over even G.711 a dice roll. > > IMO, with a sufficiently large buffer and a rock-solid quartz clocking > system that goes way beyond what is typically seen, it might be > theoretically possible to send a fax over VOIP.
Hi All, This is a good discussion. I can support most of the findings here as I have recently spent a lot of time in the lab with T38 equipment from several vendors. Interoperability is a toss up, some ATA's only work with the parent vendor gateways, some gateways are more forgiving and work with Asterisk, some ATA's work straight out of the box, others require a PHD to configure, etc..... What I ended up with for a rock solid "ON-NET" T38 gateway to T38 fax ATA is the Audiocodes Mediant 1000 with Audiocodes ATA's (MPXXX). I emphasis on-net because I control my environment end-to-end from PSTN-Data Center-T1's-Customer-QOS LAN. I was able to reliably push 100's of faxes, multi page, single page, high density, high resolution, natted ATA's, various scenarios successful. I was very excited about T38 and was convinced this was the solution I would build on. So I took one of the ATA's home to test over the Internet (great connection, low hops to my datacenter, low latency, low jitter, lots of bandwidth) and was very disappointed when I could not get more than a 3 page fax through without errors. I started getting protocol and various page errors. I tweaked every T38 parameter that Audiocodes had with zero improvement. So I have to say, my confidence in T38 is very low, at least where open Internet connections are being used. I'm now going to look at some other technology, fax over HTTPS. I will be testing the FaxBack products to see how they stack up. JR --------------------- JR Richardson Engineering for the Masses _______________________________________________ -- Bandwidth and Colocation Provided by http://www.api-digital.com -- asterisk-users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users