RFC 2833 Customization
RTP Timestamp
As a media flow with injected RFC 2833 telephone-event packets exits the Oracle® Enterprise Session Border Controller, the newly generated RTP packets are timestamped in one of two ways. If RFC 2833 generation is preformed in the NPs, the default method of creating the timestamp for a generated RFC 2833 packet is to use the previous RTP packet’s timestamp and add 1.
Alternatively, the Oracle® Enterprise Session Border Controllercan estimate the actual time that the injected RFC 2833 telephone-event packet will leave the system and use that. This method tags the injected DTMF indication packet more accurately than the than previous packet + 1 method. As an additional bonus, the packet’s checksum is regenerated. This alternate timestamp creation behavior is configured by setting the rfc2833-timestamp parameter to enabled.
When RFC 2833 telephone-event generation is preformed by the transcoding modules, the packets’ timestamps are the set to the time that the packets leave the Oracle® Enterprise Session Border Controller,.
RFC 2833 telephone-event duration intervals
- RFC2833 packet 1, digit: 5, duration 50 ms
- RFC2833 packet 2, digit: 5, duration 100 ms
- RFC2833 packet 3, digit: 5, duration 150 ms
- RFC2833 packet 4 (end packet), digit: 5, duration 160 ms
- RFC2833 packet 5 (end packet), digit: 5, duration 160 ms
- RFC2833 packet 6 (end packet), digit: 5, duration 160 ms
When either no DTMF event duration is specified, or the event duration is less than the 50ms default minimum, you can set the default RFC 2833 telephone-event duration using default-2833-duration parameter in the media manager configuration. This is the value that the Oracle® Enterprise Session Border Controller, uses for the duration of a telephone event when none is specified in the incoming message. The default-2833-duration’s valid range is 50-5000ms. The Oracle® Enterprise Session Border Controller, also uses this configured value when it receives a SIP INFO message with a duration less than the minimum signal duration.
You can configure the minimum duration at which RFC 2833 telephone-events are generated by the Oracle® Enterprise Session Border Controller, using the min-signal-duration option in the media manager configuration, thus changing the lower threshold of the default-2833-duration parameter from 50 ms to your own value. If the duration the Oracle® Enterprise Session Border Controller, receives is less than the threshold, it uses the value configured in the default-2833-duration parameter.
Note:
Timestamp changes and duration changes only take effect when the 2833 timestamp (rfc-2833-timestamp) is enabled in the media manager configuration. If you enable the rfc-2833-timestamp parameter, but do not configure the default-2833-duration parameter, the default-2833-duration parameter defaults to 100 ms.RFC 2833 End Packets
When the Oracle® Enterprise Session Border Controller, generates RFC 2833 telephone-event packets, they are forwarded from the egress interface every 50 ms by default. Each packet includes the digit and the running total of time the digit is held. Thus DTMF digits and events are sent incrementally to avoid having the receiver wait for the completion of the event.
At the conclusion of the signaled event, three end packets stating the total event time are sent. This redundancy compensates for RTP being an unreliable transport protocol.
- RFC2833 packet 1 (end packet), digit: 5, duration: 160 ms
- RFC2833 packet 2 (end packet), digit: 5, duration: 160 ms
- RFC2833 packet 3 (end packet), digit: 5, duration: 160 ms