Fax / Modem Nse Mode - AudioCodes Mediant 800B User Manual

•
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:
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.

14.2.2.5 Fax / Modem NSE Mode

In this mode, fax and modem signals are transferred using Cisco-compatible Pass-through
bypass mode. Upon detection of fax or modem answering tone signal, the terminating
device sends three to six special NSE RTP packets (configured by the NSEpayloadType
parameter; usually to 100). These packets signal the remote device to switch to G.711
coder, according to the 'Fax/Modem Bypass Packing Factor' parameter. After a few NSE
packets are exchanged between the devices, both devices start using G.711 packets with
standard payload type (8 for G.711 A-Law and 0 for G.711 Mu-Law). In this mode, no Re-
INVITE messages are sent. The voice channel is optimized for fax/modem transmission
(same as for usual bypass mode).
The parameters defining payload type for AudioCodes proprietary Bypass mode -- 'Fax
Bypass Payload Type' (RTP/RTCP Settings page) and ModemBypassPayloadType (ini file)
-- are not used with NSE Bypass.
When configured for NSE mode, the device includes in its SDP the following line:
a=rtpmap:100 X-NSE/8000
Where 100 is the NSE payload type.
The Cisco gateway must include the following definition:
modem passthrough nse payload-type 100 codec g711alaw

To configure NSE 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).
User's Manual
When the remote (non-AudioCodes) gateway uses the G.711 coder for
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Mediant 800B Gateway and E-SBC
Document #: LTRT-10286