[asterisk-users] T.38 fax between ATA's and Asterisk and Cisco PGW 2200

[Jason Aarons (US)]

WireShark does a good job showing the T38 communication. Most products you can also set packet redundancy to send 2 packets.

Your setup was T.38 ATA to T.38 Gateway with PRI/ANALOG/PSTN/G.711.  I've heard various problems with SIP/PSTN and faxing, around jitter/packet loss and it's not supported by Verizon SIP and others.

From: asterisk-users-bounces at lists.digium.com [mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of P Z
Sent: Thursday, July 29, 2010 7:49 AM
To: asterisk-users at lists.digium.com
Subject: [asterisk-users] T.38 fax between ATA's and Asterisk and Cisco PGW 2200

To provide a reliable fax solution for users connected to a Asterisk 1.6.2.6 server i have tested a few T.38 capable ATA's:
- Patton M-ATA
- Grandstream HandyTone 486
- Fritz!Box 7170

I have tried Asterisk 1.6.2.6 compiled with SpanDSP-0.0.6pre17 and also Asterisk 1.6.2.6 with Fax for Asterisk installed.

These Asterisk servers are connected to a Cisco PGW 2200 + AS5400XM.


Sending fax messages from all ATA's to the PSTN (so ATA -> Asterisk -> PGW -> PSTN) failed with a variety of error messages so i tested the different steps one by one.


ATA's -> Asterisk ReceiveFax:
So far i have only succeeded in sending fax messages from the Fritz!Box 7170 to both Asterisk configurations using the ReceiveFax application.
Sending fax messages from the other ATA's to Asterisk using the ReceiveFax application failed.


ATA's -> PGW:
To exclude Asterisk i have connected the ATA's directly to the PGW; no success either.


Asterisk -> PGW:
To exclude the ATA's i used the Asterisk SendFax application to send a TIFF file to a landline each time with a different fax machine connected to it. Results:


Asterisk 1.6.2.6 compiled with SpanDSP-0.0.6pre17 :

asterisk[1367]: WARNING[18591]: app_fax.c:223 in phase_e_handler: Error transmitting fax. result=19: Received other than DIS while waiting for DIS.
asterisk[1367]: WARNING[18591]: app_fax.c:820 in transmit: Transmission failed

asterisk[1367]: WARNING[18906]: app_fax.c:223 in phase_e_handler: Error transmitting fax. result=20: Received no response to DCS or TCF.
asterisk[1367]: WARNING[18906]: app_fax.c:820 in transmit: Transmission failed

asterisk[1367]: WARNING[18986]: app_fax.c:223 in phase_e_handler: Error transmitting fax. result=49: The call dropped prematurely.
asterisk[1367]: WARNING[18986]: app_fax.c:817 in transmit: Transmission error


Asterisk 1.6.2.6 with Fax for Asterisk :

asterisk[7092]: WARNING[3167]: res_fax.c:1529 in sendfax_t38_init: Audio FAX not allowed on channel 'SIP/out.to.pgw-000b3f49' and T.38 negotiation failed; aborting.
asterisk[7092]: ERROR[3167]: res_fax.c:1650 in sendfax_exec: error initializing channel 'SIP/out.to.pgw-000b3f49' in T.38 mode

asterisk[7092]: VERBOSE[3226]:     -- FAX handle 0: [ 028.000627 ], entering CLOSING state
asterisk[7092]: VERBOSE[3225]:     -- Channel 'SIP/out.to.pgw-000b3f72' FAX session '11' is complete, result: 'FAILED' (FAX_FAILURE_TRAINING), error: '3RD_FRM_CHECK_ERROR', pages: 0, resolution: 'unknown', transfer rate: '2400', remoteSID: ''

asterisk[7092]: WARNING[3272]: res_fax.c:1529 in sendfax_t38_init: Audio FAX not allowed on channel 'SIP/out.to.pgw-000b3f8b' and T.38 negotiation failed; aborting.
asterisk[7092]: ERROR[3272]: res_fax.c:1650 in sendfax_exec: error initializing channel 'SIP/out.to.pgw-000b3f8b' in T.38 mode


My questions:

- Does anyone have experience with T.38 fax with a setup like this: ATA -> Asterisk -> PGW -> PSTN?

- Does anyone have experience in connecting Asterisk to a Cisco PGW 2200 + AS5400XM?

- Are there any tools to debug T.38 traffic?

Thanks!



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