asterisk users - Dec 2006 - Problem faxing with SPA2100 in passthru mode.

Hi everyone,

I'm trying to send a FAX with the following configuration:

Analog FAX machine (OKI)
<----->SPA21000<----->LAN<----->Asterisk<--------> PSTN

I'm restricted to use passthru mode for faxing, instead of T.38
protocol, because the Asterisk box is running v1.2 and cannot be
changed as it is in a heavy production environment. Anyway, it
"should" work in passthru mode (G.711a) as the ATA and the Asterisk
are in the same LAN with very low traffic.

The problem arises when I try to send a fax: the Asterisk server
initiates the call and, after a few seconds, it hangs the Zaptel
channel. I'm using the following configuration in the SPA2100:

- Network jitter buffer: very high
- Jitter buffer adjustment: disable
- Call Waiting: no
- 3 Way Calling: no
- Echo Canceller: no
- Silence suppression: no
- Preferred Codec: G711a
- Use pref. codec only: yes
- Silence Threshold = medium
- Echo Canc Enable = no
- Echo Canc Adapt Enable = no
- Echo Supp Enable = no
- FAX CED Detect Enable = no
- FAX CNG Detect Enable = no
- FAX Passthru Codec = G711a
- FAX Passthru Method = NSE
- FAX Process NSE = yes
- FAX Disable ECAN = no
- FAX Codec Symmetric = yes
- DTMF Tx Method = auto
- Hook Flash Tx Method = none
- Release Unused Codec = yes

I have checked the SPA2100's logs, but I can't see anything of
interest (and I couldn't find any documentation about this logs at
Sipura's website). The ATA seems to dial correctly but, after a few
seconds, it hangs the call (CC:Failed w/ Calling)

      [0]Off Hook
      2. Report digit first_digit_of_dialed_number (1)(40 ms)
      2. Report digit second_digit_of_dialed_number (1)(40 ms)
               .... etc ...
      2. Report digit last_digit_of_dialed_number (1)(40 ms)
      Calling:dialed_number@asterisk_box_ip_address:0
      [0:0]AUD ALLOC CALL (port=16434)
      [0:0]RTP Rx Up
      [0:0]ENC INIT 8
      [0:0]RTP Tx Up (pt=8->c0a806dc:16304)
      [0:0]RTCP Tx Up
      CC:CallProgress
      [0:0]RTP Rx 1st PKT @16434(2)
      [0:0]DEC INIT 8
      [0]AUD:FAX Event=2
      [0:0]ENC INIT 8
      [0]FM Alert Stop RxTx (c=0022c1e8;a=0)
      [0:0]AUD Rel Call
      CC:Failed w/ Calling
      [0]On Hook
      Sess Terminated
      CC:Clean Up

      --- OBJ POOL STAT ---
      OP:RTPRXB =  96 ( 96  192)   OP:RTPREB =  40 ( 40   48)
      OP:RTPTXB =  64 ( 64  108)   OP:TIMEOU = 111 (120   52)
      OP:SIPCOR =   0 (  1   28)   OP:SIPCTS =  32 ( 32  568)
      OP:SIPSTS =  32 ( 32 3492)   OP:SIPAUS =   4 (  8  588)
      OP:SIPDLG =  10 ( 10  148)   OP:SIPSES =  12 ( 12 8200)
      OP:SIPREG =   3 (  4  292)   OP:SIPLIN =   0 (  2  140)
      OP:SUBDLG =   2 (  2 6436)   OP:STUNTS =  16 ( 16   68)

Has anyone suceed in sending a fax in a scenario like this? I would
appreciate any help on this point.

Best regards,

--
Mike
aster.mike NO_SPAM_AT gmail.com

> The problem arises when I try to send a fax: the Asterisk server
> initiates the call and, after a few seconds, it hangs the Zaptel
> channel.
Make sure you disable T.38 in the Sipura, "FAX Enable T38: No".
Otherwise it will reinvite using T.38 once it detects a fax tone and
Asterisk will hang up because it cannot handle T.38. That should do
it. On a local LAN, G711 should work OK.

BTW, even 1.4 only has T.38 pass through support so you need a T.38
capable PSTN gateway. Faxing with T.38 to a Asterisk with a Zapatel
hardware will not work (someone please correct me if I'm wrong).

--Luki