[Asterisk-Users] fax <-> misdn <-> zap <-> fax // fax <-> misdn <-> ATA <-> fax

[Lee Howard]

Steve Underwood wrote:

> When you are truly aware how non-optimal faxing over a VoIP channel 
> is, you will give up. :-) This isn't a joke. Its the best advice I can 
> give. Some people will tell you they have something that works. Well, 
> lucky old them. Its not a reliably reproducible phenomenon.


If my words lend any further contribution to these statements let me 
second Steve's words here.

If you understand enough of how VoIP works, and how UDP/IP 
communications work, and how modulated audio works, and how fax works, 
well, if you understand enough of this then you would understand how 
unreliable faxing over a VoIP channel is.

Those companies, such as Vonage, that sell and support fax-over-VoIP 
(not FoIP or T.38), do so on a gamble that they can somehow minimize the 
mitigating negative factors involved in faxing-over-VoIP enough that 
they can make money selling such a service.  If they can get their 
fax-over-VoIP service to work 80% of the time, and if only 5% of the 
users experience enough trouble that they cancel the service, well then, 
you can imagine that Vonage will take that gamble.  It's not that much 
different than the gamble that supermarkets make on loss-leaders and 
electronics manufacturers make on mail-in rebates.

> I assume the fax<->misdn<->zap<->fax path has a Digium TDM card 
> between zap and the fax machine. If so, this is another configuration 
> which seldom works. Some people seem to have success, but again its 
> not reproducible. There is something screwy with either the TDM400 
> card or its driver. 


And what's really interesting to me is that thus far all X100P users 
seem to be fine with faxing (at least with IAXmodem)... so it really is 
something very specific to the TDM400 or its specific part of the zaptel 
driver.

Lee.