On 02/15/2012 05:33 PM, James Sharp wrote:
On 02/15/2012 03:03 PM, Olivier wrote:
Hi,
When someone says "T.38 is not reliable on a (normally loaded and
managed) LAN", would you rather agree or disagree ?
In this case, fax calls are coming in through an analog gateway,
passing trough Asterisk and then going out to ISDN through a digital
gateway.
Comments ?
While I can't speak for Asterisk's T.38 performance (it was barely
past the point of "okay, it compiles" at the time of this datapoint),
T.38 in general can handle nasty network conditions without a problem
as long you enable some sort of error correction (either FEC or packet
redundancy). Case in point, I ran several hundred SIP-based T.38
calls a month over VSAT links. The links ran anywhere from 550 to
750ms latency and would average around 1-2% packet loss (averaged over
a 5 minute period). Those were with a Quintum ASG400 at the far end
and a Quintum CMS960 going into PRIs at the VSAT hub.
So if T.38 can handle that, it can handle just about anything.
It seems like the bigger issue is interop between different gateways and
fax machines. It seems to work 99% of the time, but that 1% is
impossible to fix if you can't control all the variables. If you
*could* control all the variables you'd probably not be faxing. :)
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