[asterisk-users] fax / t38 gateway

[Steve Underwood]

Jonn R Taylor wrote:
> I have been able to repeat the results at other locations. The location that has 26 pages is a linksys PAP2T our accounting person uses remotely to fax stuff to the office. The ATA is behind a DIL-625 router with QOS on a DSL line. 
>
> I can send faxes from my test sever at home that is using an IAX trunk to our office, same ATA. FAX--->ATA--->SIP--->Asterisk/gateway/QOS_shaper--->cablemodem--->internet--->cablemodem_office--->QOS_bridge--->asterisk/iaxmodem-hylafax So, if you look at the protocols that are used it is SIP--->IAX--->SIP--->PSTN or SIP--->IAX--->IAXmodem 
>
> This same connection is currently handling 4000 emails a day, webmail, POP, IMAP, MAPI, VPN traffic, web traffic, and normal web surfing with downloading. One test that I did with the download is started a 650MB iso download at about 900kB. Now at the same time started to send and receive faxes at the same time and worked.
>
> Jonn
>   
That signal chain is probably part of the reason you get away with this 
so often. iaxmodem does not have the real time constraints of a real FAX 
machine. Its still real time, but not as tightly constrained to a smooth 
flow of data. If packets are delayed, and jitter is high, iaxmodem can 
be very tolerant, as long as the packet loss is really low. Your QoS 
should groom things in the other direction, and ensure a reasonably 
smooth outward flow of packets.

Steve