NSE

NSE (Named Signaling Events) is a proprietary protocol to switch from voice to passthrough for fax/modem communication without involving SIP. It uses a proprietary event, based on NTE (Named Telephone Events). NTE is not proprietary, but NSE is.

TelcoBridges and NSE

We currently support NSE events:

192 (switch to passthru)
193 (disable echo)
194 (switch back to voice)

This adds a new SIP SDP entry that looks like this for initial negotiation:

a=rtpmap:100 X-NSE/8000
a=fmtp:100 192-194

The system does not send a SIP re-invite, but instead will send this NSE event 192.

Call Flow

Configuration

• Toolpack v2.7: NSE configuration

References

• RFC 2833
• list of NSE events