AudioCodes Mediant 2600 - Fax;Modem Bypass Mode

Version 6.8 161 Mediant 2600 E-SBC
User's Manual 14. Media

For G.711A-law:
a=gpmd:0 vbd=yes;ecan=on

For G.711 µ-law:
a=gpmd:8 vbd=yes;ecan=on
In this mode, the 'Fax Transport Mode' (FaxTransportMode) parameter is ignored and
automatically set to Disable (transparent mode).
 To configure fax fallback mode:

In the SIP General Parameters page (Configuration tab > VoIP menu > SIP
Definitions > General Parameters), set the 'Fax Signaling Method' parameter to Fax
Fallback (IsFaxUsed = 3).
14.2.2.4 Fax/Modem Bypass Mode
In this proprietary mode, when fax or modem signals are detected, the channel
automatically switches from the current voice coder to a high bit-rate coder, according to
the 'Fax/Modem Bypass Coder Type' parameter (FaxModemBypassCoderType). The
channel is also automatically reconfigured with the following fax / modem adaptations:

Disables silence suppression

Enables echo cancellation for fax

Disables echo cancellation for modem

Performs certain jitter buffering optimizations
The network packets generated and received during the bypass period are regular voice
RTP packets (per the selected bypass coder), but with a different RTP payload type
according to the following parameters:

'Fax Bypass Payload Type' (FaxBypassPayloadType)

ModemBypassPayloadType (ini file)
During the bypass period, the coder uses the packing factor, configured by the 'Fax/Modem
Bypass Packing Factor' parameter (FaxModemBypassM). The packing factor determines
the number of coder payloads (each the size of
FaxModemBypassBasicRTPPacketInterval) that are used to generate a single fax/modem
bypass packet. When fax/modem transmission ends, the reverse switching, from bypass
coder to regular voice coder is performed.
 To configure fax / modem bypass mode:
1. In the SIP General Parameters page (Configuration tab > VoIP menu > SIP
Definitions > General Parameters), set the 'Fax Signaling Method' parameter to No
Fax (IsFaxUsed = 0).
2. In the Fax/Modem/CID Settings page, do the following:
a. Set the 'Fax Transport Mode' parameter to Bypass (FaxTransportMode = 2).
b. Set the 'V.21 Modem Transport Type' parameter to Enable Bypass
(V21ModemTransportType = 2).
c. Set the 'V.22 Modem Transport Type' parameter to Enable Bypass
(V22ModemTransportType = 2).
d. Set the 'V.23 Modem Transport Type' parameter to Enable Bypass
(V23ModemTransportType = 2).
e. Set the 'V.32 Modem Transport Type' parameter to Enable Bypass
(V32ModemTransportType = 2).
f. Set the 'V.34 Modem Transport Type' parameter to Enable Bypass
(V34ModemTransportType = 2).
3. Set the ini file parameter, BellModemTransportType to 2 (Bypass).