I am planning to use FAX machine under Callmanager 6.1.
The documentation below says that " Use "Fax mode" when the gateways in the network do not support "Fax pass-through mode"."
Is "Fax mode" just an alternative solution when you cannot use "Fax pass-through" mode?
Does "Fax mode" have any benefit over "Fax pass-through mode"?
I would like to pick more reliable solution.
Thanks in advance.
"Fax mode" refers to fax relay (Cisco proprietary or T.38-based). Fax pass-through attempts to use a standard G.711 with VAD disabled audio call for the T.30 signals to pass through. Pass-through is extremely sensitive to packet loss and consumes lots of bandwidth by doubling the packets sent to minimize the chances of a lost packet. This sensitivity means a minor interruption or jitter will typically fail the entire fax. Relay consumes less bandwidth and can handle a packet-based network better.
The ATA186/188 do not support relay of any kind. They suck to put it bluntly. I would recommend using the VG202 or VG204 instead if you can.
Here's a lot more on the topic: