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>
>
> [EMAIL PROTECTED] schrieb:
>>> Hi all!
>>
>> Hello
>>
>>> My question is not 100% callweaver related, but I know there are
>>> several
>>> T.38 experts on the list thus I hope you can give me some hints.
>>>
>>> What is the best method to debug T.38 - e.g. I have a T.38 ATA and a
>>> T.38 capable gateway (e.g. callweaver but also others). ReINVITE to
>>> T.38
>>> works, but after some time the transmission stops and I want to find
>>> out
>>> who is guilty: the ATA? the Gateway? the analog fax?
>>>
>>> Are there any tools (beside wireshark) to debug the T.38 session? Are
>>> you aware of any tutorials for T.38 debugging?
>>
>> Wireshark is all I've ever used for T.38 debugging, it's great.
>>
>> There's a pretty detailed tutorial here, but it's Cisco oriented:
>>
>> http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123cgcr/vvfax_c/voipt_c/vts_fax.htm
>
> Hi Damjan!
>
> Thanks, this was really a good starting point. Do you know are there any
> papers/reports/personal experience about the robustness of T.38 against
> jitter/delay/loss?
Audiocodes claims it can deal with up to 400 milliseconds of jitter and 12
seconds round-trip delay (www.audiocodes.com/objects/FaxRelay.pdf). As for
packet loss, redundancy/FEC give you protection against a few lost packets
in a row, but in practice router tail-drops are bursty...
> btw I wonder about the bandwidth consumption of T.38. Is it really just
> the fax bandwidth (e.g. 14400 bits/s) plus the IP/UDP header or is there
> something else?
It's no bandwidth during V.21 preamble, 300 bits per second during the
V.21 HDLC, and up to 14400 bits per second during image transfer. Faxes
are always half-duplex. Redundancy/FEC increase these numbers, but I've
heard a T.38 fax still uses less bandwidth than a G.729 call.
> thanks
> Klaus
Bye
Damjan
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