Re: [Freeswitch-users] T.38 and Audiocodes or Patton gateway
I'm curious about your recommendation to use a long (600 sec) media/RTP timeout value in the sofia profile. Is this a specific need for the Audiocodes device or just generally better for T.38? I'm assuming you are referring to the "rtp-timeout-sec" parameter? I'm using FreeSwitch as a media proxy to a T38 provider and have had decent success, but usually have problems with longer faxes (8+ pages) and am wondering if this setting might help? Thanks, Dave Redmore ----- Original Message ----- From: "Kristian Kielhofner" <kris@kriskinc.com> To: "FreeSWITCH Users Help" <freeswitch-users@lists.freeswitch.org> Sent: Tuesday, November 16, 2010 9:39:22 AM GMT -06:00 US/Canada Central Subject: Re: [Freeswitch-users] T.38 and Audiocodes or Patton gateway Tim, I've have good experiences with the MP-20x series using T.38 with FreeSWITCH. On the AudioCodes: Make sure your T.30 and T.38 redundancy settings are at least "1". Make sure ECM is disabled. Use the latest 2.6 firmware (not 3.x). In FreeSWITCH: Make sure ECM is disabled. Make sure to have a very high (600 seconds seems ideal) media/rtp timeout parameter on the Sofia profile for the AudioCodes device. On the fax machine: Make sure ECM is disabled. Disable Super G3 or anything higher than 14.4. On Mon, Nov 15, 2010 at 1:08 PM, Tim St. Pierre <fs-list@communicatefreely.net> wrote:
Hello,
I am trying to get a reliable fax setup working.
I have set up a nice fax receiver mechanism with mod_spandsp and it works very well when I send a fax using a Linksys SPA2102
I have poor results with Audiocodes MP202B, and can't get anything to work with a Patton M-ATA
I have a number of Audiocodes MP202B in service and would rather not replace them if I can avoid it.
In each case, the fax fails with "communications error" on the sending machine, and "Call hungup prematurely" on the SpanDSP side.
There aren't too many knobs on the gateways. Are there any knobs in mod_spandsp that might help this condition? Anyone else have any experience with these devices?
Thanks!
-Tim
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-- Kristian Kielhofner http://www.astlinux.org http://blog.krisk.org http://www.star2star.com http://www.submityoursip.com http://www.voalte.com _______________________________________________ FreeSWITCH-users mailing list FreeSWITCH-users@lists.freeswitch.org http://lists.freeswitch.org/mailman/listinfo/freeswitch-users UNSUBSCRIBE:http://lists.freeswitch.org/mailman/options/freeswitch-users http://www.freeswitch.org
Dave, It's a better parameter for T.38 in general... When you look at a T.38 trace (presumably without ECM) you'll see that the T.38 data stream is entirely unidirectional. The sending device sends a stream of data - that's it. I first caught on to this with large faxes or faxes with high complexity that took a while to send. I finally found one fax page with multiple images that failed 100% of the time when being sent from FreeSWITCH to the device. Once I set the rtp-timeout-sec parameter to 600 it succeeded 100% of the time. This change was (and has been) the single biggest change I've made to my configuration to improve my T.38 success rate. Ideally FreeSWITCH could be updated with an "enhanced understanding" of the unidirectional flow of T.38 and modify/tweak/remove the RTP timeout parameter as necessary (I imagine it does something similar with silence suppression/CNG now). Or maybe I'm completely wrong and this change had no effect (I seriously doubt that). On Tue, Nov 16, 2010 at 11:14 AM, Dave Redmore <dave.redmore@spigotsystems.com> wrote:
I'm curious about your recommendation to use a long (600 sec) media/RTP timeout value in the sofia profile. Is this a specific need for the Audiocodes device or just generally better for T.38? I'm assuming you are referring to the "rtp-timeout-sec" parameter?
I'm using FreeSwitch as a media proxy to a T38 provider and have had decent success, but usually have problems with longer faxes (8+ pages) and am wondering if this setting might help?
Thanks,
Dave Redmore
-- Kristian Kielhofner http://www.astlinux.org http://blog.krisk.org http://www.star2star.com http://www.submityoursip.com http://www.voalte.com
On 11/17/2010 03:00 AM, Kristian Kielhofner wrote:
Dave,
It's a better parameter for T.38 in general...
When you look at a T.38 trace (presumably without ECM) you'll see that the T.38 data stream is entirely unidirectional. The sending device sends a stream of data - that's it. Er, no. There is is two way exchange between each page, or between each chunk of a page in ECM mode. You should require a single page that takes longer than 600s to send for this timer to expire. I first caught on to this with large faxes or faxes with high complexity that took a while to send. I finally found one fax page with multiple images that failed 100% of the time when being sent from FreeSWITCH to the device. Once I set the rtp-timeout-sec parameter to 600 it succeeded 100% of the time. This change was (and has been) the single biggest change I've made to my configuration to improve my T.38 success rate.
Ideally FreeSWITCH could be updated with an "enhanced understanding" of the unidirectional flow of T.38 and modify/tweak/remove the RTP timeout parameter as necessary (I imagine it does something similar with silence suppression/CNG now). Or maybe I'm completely wrong and this change had no effect (I seriously doubt that).
On Tue, Nov 16, 2010 at 11:14 AM, Dave Redmore <dave.redmore@spigotsystems.com> wrote:
I'm curious about your recommendation to use a long (600 sec) media/RTP timeout value in the sofia profile. Is this a specific need for the Audiocodes device or just generally better for T.38? I'm assuming you are referring to the "rtp-timeout-sec" parameter?
I'm using FreeSwitch as a media proxy to a T38 provider and have had decent success, but usually have problems with longer faxes (8+ pages) and am wondering if this setting might help?
Thanks,
Dave Redmore Steve
On Sat, Nov 20, 2010 at 10:09 AM, Steve Underwood <steveu@coppice.org> wrote:
On 11/17/2010 03:00 AM, Kristian Kielhofner wrote:
Dave,
It's a better parameter for T.38 in general...
When you look at a T.38 trace (presumably without ECM) you'll see that the T.38 data stream is entirely unidirectional. The sending device sends a stream of data - that's it. Er, no. There is is two way exchange between each page, or between each chunk of a page in ECM mode. You should require a single page that takes longer than 600s to send for this timer to expire.
Thanks for the clarification but that's exactly the behavior I saw and (not completely accurately) described. I had a single page of multiple complex images that took longer than 300 seconds to send - which was my media timeout before I bumped it to 600. Is there any chance in having the media timeouts in FreeSWITCH "tweaked" when T.38 is in use to prevent this? I can imagine people using FreeSWITCH in scenarios where they want relatively short media timeouts for traditional voice calls (RTP) and longer "timeouts" for faxes (T.38) on the same system. -- Kristian Kielhofner http://www.astlinux.org http://blog.krisk.org http://www.star2star.com http://www.submityoursip.com http://www.voalte.com
participants (3)
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Dave Redmore
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Kristian Kielhofner
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Steve Underwood