P-Dual-Info Header

The P-Dual-Info header is used in a spiral call scenario, when the call leg to (and from) the call server is set to dual. While the media portion of a spiral call goes from endpoint to endpoint through the Oracle® Enterprise Session Border Controller, the signaling portion of the call loops through a call server.

The Oracle® Enterprise Session Border Controller inserts a P-Dual-Info header into a SIP info message sent to the call server, which in turn forwards the SIP INFO message back to the Oracle® Enterprise Session Border Controller. Seeing the P-Dual-Info header, the Oracle® Enterprise Session Border Controller knows not to forward this SIP INFO message to the target endpoint because it would be a duplication of DTMF indication already sent to the endpoint in media format.