Expedited Call Leg Release for Preempted Hairpin Calls

When hairpinned calls are ended because of signaling failures (such as a SIP mid-dialog signaling timeout, or an H.323 TCP keepalive failure) on one call leg, the Oracle® Enterprise Session Border Controller deletes both legs’ media flows simultaneously by default. In addition, when the first hairpinned call leg is torn down, the second call leg is gracefully released immediately by the Oracle® Enterprise Session Border Controller creating and sending an appropriate signaling message (e.g., BYE for a SIP call or ReleaseComplete for an H.323 call) to the endpoint.

You can override this behavior by configuring the dont-terminate-assoc-legs option in the media manager. When configured, the orphaned call leg in the hairpin scenario will be torn down after the initial guard timer expires. The disconnect times of the two call legs, as recorded by the accounting appliation, will be significantly different, due to the initial guard time for the second call leg.

Accounting Considerations

To indicate cases like this, where the second leg of the hairpinned call was preempted, Oracle® Enterprise Session Border Controller includes the following combination of release/termination causes in the CDR:

VSA 49: Acct-Terminate-Cause = NAS_REQUEST
VSA 62: Acme-Disconnect-Cause = 8