[Asterisk-Users] FAX over PRI

[Roger Schreiter]

Michael Gaudette schrieb:
> I've been warned many times that Fax over VoIP is unreliable.  
> 
> How should I consider Fax over PRI channels with Asterisk?  Is the quality
> and reliability good, or should I be prepared for alot of grief?


Hi,

we tested faxing a lot. With spandsp (app_rxfax/txfax) we had
very reliable results, as long as only one or two simultanious
faxes were transmitted or received.

Than we bought a commercial DSP software, which is, according
to the manufacturer, capable of sending or recieving up
to 100 faxes simultaniously on a high perfomance machine.

Well, we tested with a dual Pentium machine, not considerable
as high perfomance machine, but we expected anyway good results.

We could drive up to 30 fax sessions at once using a TE405 Digium
card (Asterisk-1.0.10) without notable errors, more fax sessions
at once showed a slightly increasing error rate. CPU usage was
about 20% (80% idle time average).
(We've sent in total 15000 faxes in order to get reliable mean values
about the error rates.)


Roger.