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