Translation Evaluation

After SDP has been negotiated, the Oracle® Enterprise Session Border Controller determines what types of DTMF translation takes place for the call. The Oracle® Enterprise Session Border Controller sequentially evaluates the following rules for each call leg to determine what DTMF indication type it will forward to an endpoint.

1. RFC 2833—When the SDP offer/answer exchange resolves to both the Oracle® Enterprise Session Border Controller and the endpoint supporting RFC 2833 on one side of the call, the Oracle® Enterprise Session Border Controller will send DTMF indications in RFC 2833 format.
2. DTMF audio tones—Three conditions must be met for the Oracle® Enterprise Session Border Controller to support DTMF audio tones, as transcoded from another DTMF indication form:

   • The applicable codec policy’s dtmf in audio parameter is set to preferred

   • The endpoint and Oracle® Enterprise Session Border Controller have negotiated to a DTMFable codec (G711)

   • Transcoding resources are available

     Note:

     Because of rule number one, rule number two can not happen if RFC 2833 is supported in SDP—Only one media-based DTMF transfer method, RFC 2833 or DTMF audio tones may be used on a call leg.
3. If neither RFC 2833 nor DTMF Audio tones are supported on a call leg, as a result of SDP negotiation, then the Oracle® Enterprise Session Border Controller forwards DTMF indication messages to that side in signaling message format (SIP INFO).

   In the following images that illustrate DTMF transfer scenarios, a gears icon appears when relevant. This icon indicates that the Oracle® Enterprise Session Border Controller performs DTMF indication processing, creating DTMF audio tones or RFC 2833 telephone-event messages from another form of DTMF indication.