Hi there I have a SIP ATA with a fax machine attached and a SIP FXO gateway to the PSTN. When I try to send faxes in either direction, I get nothing but stony silence. I have changed the gateway and the ATA to peer to peer mode to test them and they happily do the T.38 thing and faxes flow. It seems that they initially negotiate a G.729 codec, which is what I want and then when the receiving end detects the fax machine, it wants to re-negotiate and use the t38fax codec. This is the working the Micronet devices use at least. When I put the units into proxy mode and run them through Asterisk, they fail at the negotiation stage. Now I have learned from my dealings with Asterisk and the newsgroup that Asterisk does not do T.38. However, why should it not let devices do T.38? My debug messages from Asterisk don't show it saying no, but the gateways don't wont' setup the T.38 on Asterisk. I have chanded sip.conf to allow=all and there are no explicit rules in the registrations for the gateways. Does anyone have an idea here? For this venture to be truly usable, I have to be able to get FAX working at this basic level. Regards Mark Dutton -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.digium.com/pipermail/asterisk-users/attachments/20050407/6afcdeee/attachment.htm
Mark, Try forcing ulaw on the devices, make a successful ulaw voice call, then try the fax again. Clay ________________________________ From: asterisk-users-bounces@lists.digium.com [mailto:asterisk-users-bounces@lists.digium.com] On Behalf Of Mark Dutton Sent: Thursday, April 07, 2005 7:01 AM To: asterisk-users@lists.digium.com Subject: [Asterisk-Users] T.38 fax with SIP devices Hi there I have a SIP ATA with a fax machine attached and a SIP FXO gateway to the PSTN. When I try to send faxes in either direction, I get nothing but stony silence. I have changed the gateway and the ATA to peer to peer mode to test them and they happily do the T.38 thing and faxes flow. It seems that they initially negotiate a G.729 codec, which is what I want and then when the receiving end detects the fax machine, it wants to re-negotiate and use the t38fax codec. This is the working the Micronet devices use at least. When I put the units into proxy mode and run them through Asterisk, they fail at the negotiation stage. Now I have learned from my dealings with Asterisk and the newsgroup that Asterisk does not do T.38. However, why should it not let devices do T.38? My debug messages from Asterisk don't show it saying no, but the gateways don't wont' setup the T.38 on Asterisk. I have chanded sip.conf to allow=all and there are no explicit rules in the registrations for the gateways. Does anyone have an idea here? For this venture to be truly usable, I have to be able to get FAX working at this basic level. Regards Mark Dutton -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.digium.com/pipermail/asterisk-users/attachments/20050407/33f1a12b/attachment.htm
Hello Mark, I have been working on a similar plan but am still looking for reasonable/tested hardware - can you tell me what devices you are using? Thanks, Jonathon On Apr 7, 2005 7:01 AM, Mark Dutton <replies@datamerge.com.au> wrote:> > Hi there > > I have a SIP ATA with a fax machine attached and a SIP FXO gateway to the > PSTN. When I try to send faxes in either direction, I get nothing but stony > silence. I have changed the gateway and the ATA to peer to peer mode to test > them and they happily do the T.38 thing and faxes flow. > > It seems that they initially negotiate a G.729 codec, which is what I want > and then when the receiving end detects the fax machine, it wants to > re-negotiate and use the t38fax codec. This is the working the Micronet > devices use at least. > > When I put the units into proxy mode and run them through Asterisk, they > fail at the negotiation stage. > > Now I have learned from my dealings with Asterisk and the newsgroup that > Asterisk does not do T.38. However, why should it not let devices do T.38? > My debug messages from Asterisk don't show it saying no, but the gateways > don't wont' setup the T.38 on Asterisk. > > I have chanded sip.conf to allow=all and there are no explicit rules in the > registrations for the gateways. > > Does anyone have an idea here? > > For this venture to be truly usable, I have to be able to get FAX working at > this basic level. > > Regards > > Mark Dutton > _______________________________________________ > Asterisk-Users mailing list > Asterisk-Users@lists.digium.com > http://lists.digium.com/mailman/listinfo/asterisk-users > To UNSUBSCRIBE or update options visit: > > http://lists.digium.com/mailman/listinfo/asterisk-users > >
I will give this a try Clay, but I don't think it will make a difference. When the gateway detects fax tone, it switches to T.38 and the voice codec becomes irrelevant. I am a relative novice to SIP transactions, but from what I have seen from the debug output of my gateways, the gateway first negotiates a voice codec, in this case g729. This is to be expected as this stage happens as part of the call setup. As soon as either gateway detects fax tone, the debug output of this gateway shows this detection and then it appears to re-invite with the t39fax protocol. When the gateways are in peer to peer mode, this re-invite is successful, but when all invites must be put through the asterisk server, I think Asterisk denies the T39fax protocol. This leads me to the thought, is it hard to tell Asterisk about the protocol so it will accept it? The Micronet gateways see t39fax as a codec, which makes sense and they call it "t39fax". Even though t39fax is not strictly a codec, it makes sense that gateways see it as this as for the purposes of a SIP conversation between the gateways, it looks and acts like a codec. More input on this subject is welcome. I can't be the only person who needs fax through SIP devices and T.39 is as old as the hills. I know I could turn off T.39 (actually I can't on the Micronet gateway) and use spandsp, but this is a kludge compared to the rock solid T.39 protocol. Cheers Mark Date: Thu, 7 Apr 2005 09:07:33 -0400 From: "Clay Reiche" <creiche@accxx.com> Subject: RE: [Asterisk-Users] T.38 fax with SIP devices To: "Asterisk Users Mailing List - Non-Commercial Discussion" <asterisk-users@lists.digium.com> Message-ID: <A842467212C1DC43A5D34E1C63C80C74016F8FEC@mail.accxx.com> Content-Type: text/plain; charset="us-ascii" Mark, Try forcing ulaw on the devices, make a successful ulaw voice call, then try the fax again. Clay ________________________________ From: asterisk-users-bounces@lists.digium.com [mailto:asterisk-users-bounces@lists.digium.com] On Behalf Of Mark Dutton Sent: Thursday, April 07, 2005 7:01 AM To: asterisk-users@lists.digium.com Subject: [Asterisk-Users] T.38 fax with SIP devices Hi there I have a SIP ATA with a fax machine attached and a SIP FXO gateway to the PSTN. When I try to send faxes in either direction, I get nothing but stony silence. I have changed the gateway and the ATA to peer to peer mode to test them and they happily do the T.38 thing and faxes flow. It seems that they initially negotiate a G.729 codec, which is what I want and then when the receiving end detects the fax machine, it wants to re-negotiate and use the t38fax codec. This is the working the Micronet devices use at least. When I put the units into proxy mode and run them through Asterisk, they fail at the negotiation stage. Now I have learned from my dealings with Asterisk and the newsgroup that Asterisk does not do T.38. However, why should it not let devices do T.38? My debug messages from Asterisk don't show it saying no, but the gateways don't wont' setup the T.38 on Asterisk. I have chanded sip.conf to allow=all and there are no explicit rules in the registrations for the gateways. Does anyone have an idea here? For this venture to be truly usable, I have to be able to get FAX working at this basic level. Regards Mark Dutton
Hi Jonathon. The boxes are at work, but I am pretty sure the FXO box (6port) is a Micronet SP5050/S and the FXS box (2 port) is the Micronet SP5002/S. http://www.micronet.com.tw I recommend you move to the Digium users forum. I have taken this question there. Not much feeback so far, but it is much better than this old mailing list. Cheers Mark Date: Thu, 7 Apr 2005 10:52:50 -0400 From: Moody <asterisk.user@gmail.com> Subject: Re: [Asterisk-Users] T.38 fax with SIP devices To: Asterisk Users Mailing List - Non-Commercial Discussion <asterisk-users@lists.digium.com> Message-ID: <f1cd25f80504070752613cda91@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Hello Mark, I have been working on a similar plan but am still looking for reasonable/tested hardware - can you tell me what devices you are using? Thanks, Jonathon
Right you are Michael. I have some Multitech MVP200s and they do work indeed. Only problem is mine are too old to do SIP. I know Asterisk does not do T.39 but as it only needs to ALLOW the codec when devices are communicating with each other, it can't be too hard to get working. Perhaps the t39fax codec needs to be added to the Asterisk codec list so it knows about it and then it can be added to the allow list in SIP. Mark Date: Thu, 07 Apr 2005 21:17:03 -0700 From: Michael D Schelin <mike@shelcomm.com> Subject: Re: [Asterisk-Users] T.38 fax with SIP devices To: Scott Wolfe <scottwolfe@orbus.net>, Asterisk Users Mailing List - Non-Commercial Discussion <asterisk-users@lists.digium.com> Message-ID: <425605BF.1080908@shelcomm.com> Content-Type: text/plain; charset="us-ascii" Hello, The Multitech VOIP line supports T38 and I have tested it. It works great. You will need a public IP to make it work. Very expensive though. T38 Is not compatible with Asterisk.