[Asterisk-Users] Clarification - FAX on local network

[Lee Howard]

On 2004.09.14 11:10 Marty Mastera wrote:
> Ok, ok, I know there has been plenty of discussion on asterisk and fax
> -
> from this I understand:
> 
> 1)    First and foremost, use g.711 ulaw

Yes, the codec must be lossless.

> 2)    Packet loss, etc...makes faxing over the internet unreliable

I'm not sold on this theory yet.  I don't think that it's so much a 
matter of packet loss (this shouldn't occur regularly), but rather of 
latency.  Transmitting packets over a network, and in particular the 
internet, can result in latency delays that could, in theory, pose a 
problem for FoIP, but I've heard of so many people successfully doing 
FoIP with equipment other than Asterisk (i.e. using Cisco VoIP 
equipment), that I tend to believe that the reliability factor is more 
a consequence of SIP or the equipment used (Asterisk and, in my case, a 
Sipura SP-2000).

I have used a HylaFAX system connected to an SP-2000 for both sending 
and receiving faxes.  The fax call comes in to an FXO on the Asterisk 
server, which directs it over a small LAN to the Sipura.  This 
arrangement works tolerably well, but it's quite noticeably 
less-reliable than when the HylaFAX server is connected directly to the 
PSTN.  I don't know if the Sipura is to blame or if it's Asterisk, or 
if it's SIP design.  Although I've used a number of IAXys for voice, I 
haven't tried using one instead of the Sipura for fax.  (Testing that 
would be able to eliminate or isolate SIP+Sipura.)

Lee.