Preferred RFC 2883 Support

Setting a signaling interface or session agent’s RFC 2833 mode to preferred indicates that the RFC 2833 telephone-event DTMF transfer method is the preferred method for sending a DTMF indication. In the capability negotiation phase a telephone-event media type will be inserted in the outgoing SDP offer, if it was not present in the original offer.

1. In the following example RFC 2833 mode is set to preferred on the egress side of the call. Because there is no telephone-event in the SDP, and RFC 2833 mode is set to preferred, the Oracle® Enterprise Session Border Controller adds telephone-event to the SDP offer.
   
2. In the following example, RFC 2833 is set to preferred mode on the SDP offer side of the call. The Oracle® Enterprise Session Border Controller maintains the telephone-event support even though telephone-event is not supported on the SDP answerer’s side of the call.