Fax Bypass Method; Configuring Fax Failover - Patton electronics SmartWare R.3.20 Software Configuration Manual

SmartWare Software Configuration Guide
Mode: profile voip profile-name
Step
1 [ name ] (pf-voip)[name]#[no] fax ced-
retransmission number

Fax bypass method

This command specifies the method for notifying the remote device that the RTP Stream has switched to a
voice-band FAX transmission. This feature is only available on the SIP protocol. If the command option 'v150-
vbd' is selected, a re-invite is sent even if the current voice coder is configured the same as the fax bypass coder.
Furthermore the re-invite contains a gpmd-attribute line with the value 'vbd=yes' in the media description
part. It signals the remote device of the new media transmission. If the command option 'default' is selected,
the system behavior is the same as before.
For a fax transmission over a VoIP (SIP or H.323) network, the Cisco NSE standard uses events defined by
RFC2833. These events are used for the setup of the fax transmission starting between the calling- and called-
peer. Upon detecting a fax transmission, the called-peer issues NSE Event 192. NSE Event 192 indicates the
data stream is via a voice band, and it forces the calling-peer to do two things—deactivate voice activity detec-
tion and reconfigure the de-jitter buffer for data reception. The option 'nse' enables this fax transmission stan-
dard.
Mode: profile voip
Step
1
[ name ] (pf-voip)[name]#fax bypass-
method {default | v150-vbd|nse}
Configuring fax failover
When using fax transmission in SIP, it is possible configure the SIP gateway to first try to use T.38 and to fall
back to a high-rate codec, if the remote gateway does not support T.38. This can be configured as follows:
Mode: profile voip <pf-name>
Step
1
[ name ] (pf-voip)[pf-name]# fax
transmission 1 relay t38-udp
2
[ name ] (pf-voip)[pf-name]# fax
transmission 2 bypass
g711alaw64k
Note
The first codec must always be T.38, while the second one must be a high-
rate codec such as G.711, which supports fax transmission.
VoIP profile configuration task list
Command
Command
Command
40 • VoIP profile configuration
Purpose
Specifies the number of CED retransmissions.
Default: 2
Purpose
Specifies the fax bypass signaling method.
Default: default
Purpose
Define T.38 UDP as the first fax transmission
method to try
Define G.711 A-Law as the second fax transmis-
sion method to try, if T.38 is not supported by the
remote gateway.
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