[Asterisk-Users] Asterisk in production as a fax server, anyone?

[Lee Howard]

Adolfo R. Brandes wrote:

>     After combing these lists for clues, we began experimenting 
> extensively with Asterisk and its software DSP and fax capabilities in 
> most of their incarnations, such as Rxfax or Iaxmodem/Hylafax, 
> together with Digium's E1 cards in server-grade Intel motherboards, 
> all in a dedicated test environment.
>
>     Unfortunately, though, we have yet to achieve reliable and 
> satisfactory results, even with only 1 fax call at a time.


Well, if you weren't just trying to test you could send some logs to an 
appropriate mailing list (like iaxmodem-users or whatever would be most 
appropriate), and you'd probably get a very quick indication as to why.

However, based on the comments you give I'd suspect that you're having 
what people seem to be calling "frame slipping".  There seem to be some 
motherboards that react poorly with Zap cards (or their respective 
drivers) and cause that.  Your zttest results should be revealing here.  
I don't know that anyone has yet proposed a conclusive solution to that 
matter other than to keep trying different motherboards until you find 
one that works.

> I won't go into the details because we don't need technical support, 
> given that this is, as of yet, a very loosely defined test.  What we 
> want is is merely a pointer in the right direction. So here it comes:
>
>     Has anybody ever achieved, or know of someone who has, reliable 30 
> simultaneous PRI fax calls using Asterisk and Asterisk-compatible 
> hardware and software?


Yes.  The concurrent calls really isn't that big of a deal, either, if 
those are your thoughts.  The bigger issue seems to be the quality of 
the audio as it is delivered to the fax application/modem.

>     We are hardware agnostic, so if you say Sangoma's cards do it 
> better than Digium's, or that Eicon Diva cards' hardware DSP and 
> chan_capi are the only solution, we have no problem going there.


In my experience Sangoma offers better (or maybe just more caring) 
post-sale support than does Digium, however, the "frame slipping" issue 
seems to happen with both sets of hardware.  Maybe that's because 
Sangomas partially use the zaptel driver as well as does the Digium 
hardware.  As for Eicon Divas being used for IVR, I've never used them 
that way.

> I would be most thankful, however, for detailed explanations of 
> successful scenarios, including such things as motherboard make and 
> model, processor speed, Linux distribution and version, and anything 
> else you decide to be even marginally pertinent. 


The most success I've seen has been to bridge the call through Asterisk 
to a T1 fax modem such as a Patton 2977 or an Eicon Diva Server with 
HylaFAX running the modems.  (So you put a crossover cable between the 
T1/E1 fax modem and one of the ports on your TE405P card and bridge the 
fax call, after IVR, to the fax port and let HylaFAX take it from there.)

That said, I see no reason why you couldn't have just as much success 
with iaxmodem-hylafax or even txfax/rxfax... I just haven't personally 
used either of those as much as I have the T1-faxmodem solution.

Lee.