1. ACLI Configuration Guide
  2. DTMF Transfer and Support
  3. RFC 2833 Customization

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

If an incoming SIP INFO message’s DTMF indication duration is unspecified, the Oracle® Enterprise Session Border Controller, uses a default 250 ms duration for the generated RFC 2833 telephone-event. Otherwise, the SIP INFO’s specified event duration is used. RFC 2833 telephone-event packets are still generated at 50 ms intervals upon egress. At the conclusion of the DTMF indication, the three end-event packets are sent. The packet arrangement when the user presses the digit 5 for 160ms, with the default 50ms interval follows:
  1. RFC2833 packet 1, digit: 5, duration 50 ms
  2. RFC2833 packet 2, digit: 5, duration 100 ms
  3. RFC2833 packet 3, digit: 5, duration 150 ms
  4. RFC2833 packet 4 (end packet), digit: 5, duration 160 ms
  5. RFC2833 packet 5 (end packet), digit: 5, duration 160 ms
  6. 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.

You can configure your Oracle® Enterprise Session Border Controller, to generate either the entire start-interim-end RFC 2833 packet sequence or only the last three end 2833 packets for non-signaled digit events using the rfc2833-end-pkts-only-for-non-sig parameter. If the parameter were enabled, the RFC 2833 telephone-event packets for the same event would appear as follows:
  1. RFC2833 packet 1 (end packet), digit: 5, duration: 160 ms
  2. RFC2833 packet 2 (end packet), digit: 5, duration: 160 ms
  3. RFC2833 packet 3 (end packet), digit: 5, duration: 160 ms

ACLI Instructions and Examples

To configure RFC 2833 customization:

  1. In Superuser mode, type configure terminal and press Enter. 
    ORACLE# configure terminal
  2. Type media-manager and press Enter to access the media-level configuration elements. 
    ORACLE(configure)# media-manager
ORACLE(media-manager)#
  3. Type media-manager and press Enter to begin configuring this feature. 
    ORACLE(media-manager)# media-manager
ORACLE(media-manager-config)#
  4. rfc2833-timestamp—Set this parameter to enabled to use the estimated real departure timestamp on an injected RFC 2833 telephone-event packet.
  5. default-2833-duration—Set this parameter to the default value you wish to use when the Oracle® Enterprise Session Border Controller, creates or generates DTMF-indication messages.
  6. rfc2833-end-pkts-only-for-non-sig—Set this parameter to enabled for the Oracle® Enterprise Session Border Controller, to only send the three RFC 2833 telephone-event end-packets to indicate a total event duration, rather than the running total from time=0.
  7. options—Set the options parameter by typing options, a Space, the option name min-signal-duration=x (where x is the value in milliseconds you want to use for the threshold) with a plus sign in front of it. Then press Enter.
  8. Save and activate your configuration.