On Mon, 2008-06-02 at 00:54 +0300, Dovid Bender wrote: > Hi List, > I was thinking the other day that even with T.38 there are still some > issues with faxing. I was thinking of a protocol that instead of just > sending down the fax tones an ATA or "VOIP fax machine" would get the > entire fax convert it into some sort of image and pass it down the > line to the receiving end. I got the idea from RFC2833. Yes I know > that fax machines send bit by bit and get a conformation on it but > maybe this would work a bit better. Send the entire "image" over and > then get a response when it is done. This way if there is issues along > the way the packets can be re-sent with out any issue. > > Dovid > (Cross posted to Biz for those that aren't on the users list - I want > their onion too ;) ).
first t.38 is a codec not a protocol as that word is commonly defined. :) What you are describing is similar to T.37, which uses smtp, mime and all that and is in essence store and forward. The reason for T.38 is so that the capabilities of each of the two endpoints can be agreed upon. With T.37 for example, the least common matching features between the two endpoints and the gateway in the middle are what ends up being used. RFC2833 lets you represent tones, you could in theory use that, however I wouldnt recommend it as many devices do not properly support RFC2833 tones, and to convert the tones that way really provides little benefit and is likely to trash the data. T.38 has some redundancy built in, or at least its supposed to, so that "this frame" and "last frame" are sent, so any single frame lost can be recovered with the next one. One issue is that not everyone implements T.38 the same way, kinda like SIP, RFC2833, and some others. If you dont have a *really* good T.38 implementation that can identify and deal with all the quirks you are potentially going to have issues somewhere with some devices. -- Trixter http://www.0xdecafbad.com Bret McDanel Belfast +44 28 9099 6461 US +1 516 687 5200 http://www.trxtel.com the phone company that pays you! _______________________________________________ --Bandwidth and Colocation Provided by http://www.api-digital.com-- asterisk-biz mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-biz
