This feature terminates a superfluous session as part of access transfer procedures .

Feature cheat sheet

B2BUA Instance Originating / Terminating Point(s) in Session Plan Network Operator Data Subscriber Data Stateful or Stateless POJO or SBB Feature Other notes

SCC

Both Originating and Terminating

 
SipTransaction_Request

None

None

Stateless

POJO

Prerequisite features

None.

Session input and output variables

Session input variables

None.

Session output variables

None.

Statistics

SCCRemoveSuperfluousSession statistics are tracked by the volte.sentinel.sip SBB and can be found under the following parameter set in REM:
SLEE-Usage → volte.sentinel.sip service → volte.sentinel.sip SBB → feature → SCCRemoveSuperfluousSession
or with rhino-stats:
"SLEE-Usage.Services.ServiceID[name=volte.sentinel.sip,vendor=OpenCloud,version=2.7.0].SbbID[name=volte.sentinel.sip,vendor=OpenCloud,version=2.7.0].feature.SCCRemoveSuperfluousSession"

Name Description 
Started

Incremented each time the feature runs

 
FailedToStart

Incremented when a fatal error occurs before feature execution

 
IssuedWarning

Incremented when a non-fatal error occurs during feature execution

 
FailedDuringExecution

Incremented when a fatal error occurs during feature execution

 
TimedOut

Incremented when feature execution does not complete within a reasonable time frame

 
TriggeredOnSipRequest

Incremented when the feature is triggered by a SIP MESSAGE request from another node

 
TriggeredOnAccessTransferRequest

Incremented when the feature is triggered by an internal AccessTransferRequest event from the same node

 
SentMessageResponse

Incremented when a response to the triggering MESSAGE request is successfully sent

 
SessionTerminated

Incremented when the session is terminated

Behaviour

Background

This feature is one part of the SCC Access Transfer system. It is triggered on an existing INVITE session by a SIP MESSAGE request, which directed into the session by the SCCSendRequestToAnchor feature.

Feature Execution

When invoked, the feature will perform a check to ensure that it was triggered by an incoming SIP request; if not, the feature will complete execution raising an unsupported trigger error. If the trigger is an incoming SIP request, additional checks will be made to determine if the request is both a MESSAGE request, and has an OC-Access-Transfer-Procedure header with the value Remove-Superfluous. If either of those checks fail, the feature will ignore the request and complete execution normally.

If the trigger is confirmed to be an incoming SIP MESSAGE request with the appropriate header, the feature will do two things before completing execution:

  1. Immediately send a SIP 200 OK response for the MESSAGE request.

  2. Terminate the session using the appropriate procedure based on the call state:

    • For sessions still being established, a 404 Not Found response for the initial INVITE will be sent upstream and a CANCEL request will be sent downstream.

    • For established sessions, a BYE will be sent in both directions.

If 200 OK response for the MESSAGE request fails to send for any reason, the feature will raise an error, but will still attempt to end the session.

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Sentinel VoLTE Version 2.7.0