User`s manual

SIP User's Manual 8. Telephony Capabilities
Version 5.0 221 December 2006
8.3.4 Supporting V.34 Faxes
V.34 faxes don’t comply with the T.38 relay standard. We therefore provide the optional
modes described under Sections 8.3.4.1 and 8.3.4.2:
Note that the CNG detector is disabled (CNGDetectorMode=0) in all the following
examples.
8.3.4.1 Using Bypass Mechanism for V.34 Fax Transmission
In this proprietary scenario, the media gateway uses a high bit-rate coder to transmit V.34
faxes, enabling the full utilization of its speed.
Refer to the following configurations:
FaxTransportMode = 2 (Bypass)
V34ModemTransportType = 2 (Modem bypass)
V32ModemTransportType = 2
V23ModemTransportType = 2
V22ModemTransportType = 2
In this configuration, both T.30 and V.34 faxes work in Bypass mode.
Or
FaxTransportMode = 1 (Relay)
V34ModemTransportType = 2 (Modem bypass)
V32ModemTransportType = 2
V23ModemTransportType = 2
V22ModemTransportType = 2
In this configuration, T.30 fax uses T.38 Relay mode while V.34 fax uses Bypass mode.
8.3.4.2 Using Relay mode for both T.30 and V.34 faxes
In this scenario, V.34 fax machines are compelled to use their backward compatibility with
T.30 faxes; as a T.30 machine, the V.34 fax can use T.38 Relay mode.
Refer to the following configuration:
FaxTransportMode = 1 (Relay)
V34ModemTransportType = 0 (Transparent)
V32ModemTransportType = 0
V23ModemTransportType = 0
V22ModemTransportType = 0
Both T.30 and V.34 faxes use T.38 Relay mode. This configuration forces the V.34 fax
machine to operate in the slower T.30 mode.