[azx]

Hi again.

Thanks for the help regarding fax so far.

But Im back

Im testing fax possibilites over satelite (Norway - Africa)
To do this I use FreeBSD and dummynet to simulate.

The script Im using is this:
#!/bin/sh

ipfw -q flush

ipfw pipe 1 config delay 250ms
ipfw pipe 2 config delay 300ms
ipfw pipe 3 config delay 275ms
ipfw pipe 4 config delay 320ms

ipfw add prob 0.25 pipe 1 ip from any to any
ipfw add prob 0.25 pipe 2 ip from any to any
ipfw add prob 0.25 pipe 3 ip from any to any
ipfw add pipe 4 ip from any to any

Our ping time is around 500 - 600ms. Ive set the seppura 2000 box to jitter level very high.

But Im not able to fax, if I turn off dummynet the fax works every time.
(and it works with a stable ping of 600ms). But it dont like the jittering.

Any thoughts around this, all info are appriciated

[azx]

Im sorry for all the rambling about this. Tell me to shut up and I try to find another way to solve this

Since I was able to test the jitter, Ive run into another problem. Im sure the fax can handle some jitter'ing, but the fax cant understand the way its gets the packets.
So Im now faced with the problem to run the same teste, but with "packet reordering" So I can be sure that the client fax gets the packets in the right order.

So if anyone with the skills can explain me this I would be very happy.
Feel free to think out loud, that is what Im doing now

[mberlant]

What you are looking for is called T.38. Fax and VoIP are oil and water. Fax does not tolerate compression, so you are limited to a lossless CODEC like G.711. And, fax does not tolerate dropped packets, so you have to constrain your fax speed to 9600 (or less, if you can) to "slow down" the packets to give them a better chance of getting through.

T.38 adds back in the end-to-end Layer 3 controls that TCP/IP stripped out of X.25 when it coopted the protocol. T.38 is typically implemented in firmware and it must be at both ends of the IP connection to work. That means that you must have it in your ATA and your service provider must have it in its PSTN gateway.

[azx]

T.38 isnt supported by our gateway yet, but will be in the future .... (sometime)

But I feel Im on the right track testwise, all I need to figure out to do the final test is how to reordering my packets.