AudioCodes Mediant 500L MSBR

User's Manual 17. Media
Version 6.8 187 Mediant 500L MSBR
17.2.2.5 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).
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. Set the ini file parameter, NSEMode parameter to 1 (enables NSE).
5. Set the ini file parameter, NSEPayloadType parameter to 100.
17.2.2.6 Fax / Modem Transparent with Events Mode
In this mode, fax and modem signals are transferred using the current voice coder with the
following automatic adaptations:

Echo Canceller = on (or off for modems)

Echo Canceller Non-Linear Processor Mode = off

Jitter buffering optimizations
 To configure fax / modem transparent with events 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).