AudioCodes Mediant 500L MSBR

User's Manual 186 Document #: LTRT-10466
Mediant 500L MSBR
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).
4. Configure the following optional parameters:
• 'Fax/Modem Bypass Coder Type' (FaxModemBypassCoderType).
• 'Fax Bypass Payload Type' (FaxBypassPayloadType) - in the RTP/RTCP
Settings page (Configuration tab > VoIP menu > Media > RTP/RTCP Settings).
• ModemBypassPayloadType (ini file).
• FaxModemBypassBasicRTPPacketInterval (ini file).
• FaxModemBypasDJBufMinDelay (ini file).
Note: 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.
Tip: 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.