AudioCodes Mediant 3000 User Manual page 940

Parameter
[T38MaxDatagramSize]
T38 Fax Max Buffer
[T38FaxMaxBufferSize]
Detect Fax on Answer Tone
[DetFaxOnAnswerTone]
CED Transfer Mode
[CEDTransferMode]
T.38 Fax Session
[T38FaxSessionImmediateStart
]
User's Manual
used.
The valid range is 120 to 600. The default is 560.
Defines the maximum size (in bytes) of the device's T.38 buffer.
This value is included in the outgoing SDP when T.38 is used for
fax relay over IP.
The valid range is 500 to 3000. The default is 3000.
Determines when the device initiates a T.38 session for fax
transmission.

[0] Initiate T.38 on Preamble = (Default) The device to which the
called fax is connected initiates a T.38 session on receiving V.21
Preamble signal from the fax.

[1] Initiate T.38 on CED = The device to which the called fax is
connected initiates a T.38 session on receiving a CED answer
tone from the fax. This option can only be used to relay fax
signals, as the device sends T.38 Re-INVITE on detection of any
fax/modem Answer tone (2100 Hz, amplitude modulated 2100
Hz, or 2100 Hz with phase reversals). The modem signal fails
when using T.38 for fax relay.
Note: The parameters is applicable only if the IsFaxUsed
parameter is set to 1 (T.38 Relay) or 3 (Fax Fallback).
Defines the method for sending fax/modem CED (answering) tones.

[0] Fax Relay or VBD = (Default) The device transfers the CED
tone in Relay mode and starts the fax session immediately.

[1] Voice Mode or VBD = The device transfers the CED tone in
either Voice or Bypass mode and starts the fax session on V21
preamble.

[2] RFC 4733 Blocking RTP VBD = The device transfers the
CED tone in RFC 2833. This is applicable only to V.150.1
modem relay and fax bypass.

[3] RFC 4733 Along with RTP VBD = The device transfers the
CED tone in RFC 2833 and bypass, in parallel. For combined
V.150.1 modem relay and fax relay, use this option.
Note: The parameter is applicable only to the Gateway application.
Enables fax transmission of T.38 "no-signal" packets to the
terminating fax machine.

[0] Disable (default)

[1] Immediate Start on Fax = Device activates T.38 fax relay
upon receipt of a re-INVITE with T.38 only in the SDP.

[2] Immediate Start on Fax & Voice = Device activates T.38 fax
relay upon receipt of a re-INVITE with T.38 and audio media in
the SDP.
The parameter is used for transmission from fax machines
connected to the device and located inside a NAT. Generally, the
firewall blocks T.38 (and other) packets received from the WAN,
unless the device behind NAT sends at least one IP packet from
the LAN to the WAN through the firewall. If the firewall blocks T.38
packets sent from the termination IP fax, the fax fails.
To overcome this, the device sends No-Op ("no-signal") packets to
open a pinhole in the NAT for the answering fax machine. The
originating fax does not wait for an answer, but immediately starts
940
Description
Document #: LTRT-89730
Mediant 3000