AudioCodes Mediant 4000 SBC - Page 195

CHAPTER15 Media
Mediant 4000 SBC | User's Manual
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. On the Fax/Modem/CID Settings page, do the following:
● Set the 'Fax Transport Mode' parameter to Bypass (FaxTransportMode = 2).
● Set the 'V.21 Modem Transport Type' parameter to Enable Bypass
(V21ModemTransportType = 2).
● Set the 'V.22 Modem Transport Type' parameter to Enable Bypass
(V22ModemTransportType = 2).
● Set the 'V.23 Modem Transport Type' parameter to Enable Bypass
(V23ModemTransportType = 2).
● Set the 'V.32 Modem Transport Type' parameter to Enable Bypass
(V32ModemTransportType = 2).
● Set the 'V.34 Modem Transport Type' parameter to Enable Bypass
(V34ModemTransportType = 2).
2. Set the ini file parameter, BellModemTransportType to 2 (Bypass).
3. Configure the following optional parameters:
● 'Fax/Modem Bypass Coder Type' (FaxModemBypassCoderType).
● 'Fax Bypass Payload Type' (FaxBypassPayloadType).
● ModemBypassPayloadType (ini file).
● FaxModemBypassBasicRTPPacketInterval (ini file).
● FaxModemBypasDJBufMinDelay (ini file).
● When the device is configured for modem bypass and T.38 fax, V.21 low-speed
modems are not supported and fail as a result.
● When the remote (non-AudioCodes) gateway uses the G.711 coder for voice and
doesn’t change the coder payload type for fax or modem transmission, it is
recommended to use the Bypass mode with the following configuration:
✔ EnableFaxModemInbandNetworkDetection = 1.
✔ 'Fax/Modem Bypass Coder Type' = same coder used for voice.
✔ 'Fax/Modem Bypass Packing Factor'(FaxModemBypassM) = same interval as
voice.
✔ ModemBypassPayloadType = 8 if voice coder is A-Law or 0 if voice coder is
Mu-Law.
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