Sorry, Fat fingered that one. G3. I've had instances with some fax machines that receive a call from a like machine and they determine that they are Super G3 compatible, they turn ECO back on when it is turned off. I think its a Panasonic if I'm not mistaken. You think everything is working fine, and then intermittently, you get faxes that don't work. You scramble around playing with gateways, etc. to find it was a fax machine all along. It's that Super G3 tone that is being manhandled by one ITSP to improve their fax service over their IP network. It's a real problem for the ITSP's, although many don't admit it, while others openly say its a problem.
I've not ran into T.38 redundancy. It's been a while since I read the spec's on T.38, but from what I remember, T.38 since it has no error correction, transmits each packet multiple times as its form of ensuring the data gets to the other side. If my memory serves me, what I remember reading is that the standard doesn't say how many times to transmit it, that it's up to the sender to determine how many times to transmit the data. I did a quick google on T.38 redundancy and Cisco was saying in their configuration that it determines the number of times the data is transmitted. It didn't go into great detail, but lead me to believe that they allow theirs to be configurable maybe? I'm by no means an expert on this subject, I just have a few more grey hairs from it having fought issues from it with some larger customers. Sometimes it's to easy to point a finger at something we don't understand, when the real issue is really another component on the network. I'm only suggesting people not ignore that their fax issues could actually be the fax machines and their inability to play within the constrictions of T.38. And, its a really easy thing to check out. One big key, if you get one page and then it drops each time, check ECO. -----Original Message----- From: Jan Schumacher [mailto:[email protected]] Sent: Wednesday, June 10, 2009 11:36 PM To: [email protected]; [email protected] Subject: Re: [sipx-users] fax compatibility list? Hi Todd, what did you mean with G5 fax machine? Is it a T.38 IP fax machine? Is it better to turn off the T.38 redundancy too? Jan 2009/6/11 Todd Hodgen <[email protected]>: > Are you sure the issue is with the Gateway itself and not the fax machines. > It's important on the faxes to turn off Error Correction. And, it gets > trickey, because some machines allow you to turn them off, some require the > manufacturer to turn them off, and some turn back on by themselves when they > detect a G5 fax machine. Error Correction must be turned off for Faxing to > work in an IP network. I learned this lesson the hard way with some large > Nortel CS1000 implementations. Problem wasn't the switch, but the fax > machines on the ends, and the T.38 protocol itself. > > I know of at least one ITSP's that's even beginning to tweak their network > now to ensure error correction is stripped off of their network entirely to > improve fax capabilities. > > Voipfrustration.com is a sight that has instructions for turning off Error > Correction on different Fax Machines, it can be helpful when things are > coming together. > > > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Matt Keys > Sent: Wednesday, June 10, 2009 9:42 PM > To: [email protected] > Subject: [sipx-users] fax compatibility list? > > Is there a list of sipxecs tested/certified ATAs that work for faxing? I > was able to get a SPA-2102 to send/receive yesterday. Tests using a > AudioCodes MP-112 (version 5 firmware) have failed. > > FYI - I just discovered HP has a very handy tool available. Call > 1-888-hpfaxme (1-888-473-2963) and it will receive your test fax and > send it back to you. See > http://h10025.www1.hp.com/ewfrf/wc/document?docname=c00259105&lc=en&dlc=&cc= > us&product=424230 . > > > _______________________________________________ > sipx-users mailing list [email protected] > List Archive: http://list.sipfoundry.org/archive/sipx-users > Unsubscribe: http://list.sipfoundry.org/mailman/listinfo/sipx-users > sipXecs IP PBX -- http://www.sipfoundry.org/ > > _______________________________________________ > sipx-users mailing list [email protected] > List Archive: http://list.sipfoundry.org/archive/sipx-users > Unsubscribe: http://list.sipfoundry.org/mailman/listinfo/sipx-users > sipXecs IP PBX -- http://www.sipfoundry.org/ > _______________________________________________ sipx-users mailing list [email protected] List Archive: http://list.sipfoundry.org/archive/sipx-users Unsubscribe: http://list.sipfoundry.org/mailman/listinfo/sipx-users sipXecs IP PBX -- http://www.sipfoundry.org/
