Fax / Modem Nse Mode - AudioCodes MP-124 User Manual

SIP User's Manual
7.2.2.3
Version 5.2
http://ArtTel.ru
V32ModemTransportType = 2
V34ModemTransportType = 2
BellModemTransportType = 2
Additional configuration parameters:
•
FaxModemBypassCoderType
•
FaxBypassPayloadType
•
ModemBypassPayloadType
•
FaxModemBypassBasicRTPPacketInterval
•
FaxModemBypassDJBufMinDelay
When the gateway is configured for modem bypass and T.38 fax, V.21 low-
Notes:
speed modems are not supported and fail as a result.

Fax / Modem NSE Mode

In this mode, fax and modem signals are transferred using Cisco-compatible Pass-through
bypass mode. On detection of fax or modem answering tone signal, the terminating
gateway sends three to six special NSE RTP packets (using NSEpayloadType, usually
100). These packets signal the remote gateway to switch to G.711 coder (according to the
parameter FaxModemBypassCoderType). After a few NSE packets are exchanged
between the gateways, both gateways 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 the proprietary AudioCodes' Bypass mode
FaxBypassPayloadType and ModemBypassPayloadType are not used with NSE Bypass.
When configured for NSE mode, the gateway 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, perform the following configurations:
IsFaxUsed = 0
FaxTransportMode = 2
NSEMode = 1
NSEPayloadType = 100
V21ModemTransportType = 2
V22ModemTransportType = 2
V23ModemTransportType = 2
V32ModemTransportType = 2
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7. Telephony Capabilities
September 2007