SIP fax sending software?
John Osmon
josmon at rigozsaurus.com
Thu May 31 05:46:00 UTC 2018
On Thu, May 31, 2018 at 12:54:05AM -0400, John R. Levine wrote:
> >You *can* get a fax across a G.711 connection if your throughput,
>
> My SIP provider supports T.38. How much difference does that make?
It can make a great deal of difference.
You change the dynamics from:
fax ------------ fax
modem <-> VOIP <-> modem
------------
Into something more like:
T.38 service
fax ----------------------------- fax
modem <-> modem <-> IP <-> modem <-> modem
-----------------------------
Fax communications have a data envelope that don't play well with
anything that has latency/jitter/loss issues that don't act/feel like
a POTS system. Also, the envelope doesn't recover well from errors.
So --- faxes fail.
So, you terminate the envelop at each end, and plug them together with
and IP connection. You may still have problems, but a single issue
doesn't necessarily mean that you have to terminate the transmission and
start over.
More (and better/more accurate) details with the article I linked
earlier: http://www.soft-switch.org/foip.html
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