This feature uses the Leg Manager to get the names of the original SIP legs established during call set up, and saves the values to a set of session state fields that may be used by other VoLTE features when they need to access a specific leg by name.

Feature cheat sheet

B2BUA Instance Originating / Terminating Point in Session Plan Network Operator Data Subscriber Data Stateful or Stateless POJO Feature or SBB Feature

Both or either of MMTEL or SCC

Originating and Terminating

SIPAccess_*PreCreditCheck AND SIPAccess_PartyResponse

No

No

Stateless

POJO

Prerequisite features

These features must run before DetermineInitialLegNames:

  • DetermineCallType

Session input and output variables

Session input variables

Session state variable name Variable type 
CallType

Enum

Session output variables

Session state variable name Variable type Comments 
CurrentLocalLegName

String

The name of the leg towards the local UE (that is, the calling party on an originating instance, or the called party on a terminating instance)

 
CurrentRemoteLegName

String

The name of the leg towards the remote UE (that is, the called party on an originating instance, or the calling party on a terminating instance)

 
CurrentCallingLegName

String

The name of the leg towards the calling party

 
CurrentCalledLegName

String

The name of the leg towards the called party

Statistics

DetermineInitialLegNames statistics are tracked by the volte.sentinel.sip SBB and can be found under the following parameter set: SLEE-Usage → volte.sentinel.sip service → volte.sentinel.sip SBB.

Name Description 
DetermineInitialLegNamesFeatureStarted

Incremented each time the feature runs

 
DetermineInitialLegNamesFeatureFailedToStart

Incremented when sentinel VoLTE encounters an error while attempting to start the feature

 
DetermineInitialLegNamesFeatureIssuedWarning

Incremented when a non-fatal problem is encountered and the feature and issues a warning

 
DetermineInitialLegNamesFeatureFailedDuringExecution

Incremented when a fatal problem is encountered and the feature cannot execute correctly

 
DetermineInitialLegNamesFeatureTimedOut

Incremented when the feature takes too long to complete and Sentinel VoLTE aborts execution

 
DetermineInitialLegNamesFeatureCallingLegNameSet

Incremented when calling leg name is found

 
DetermineInitialLegNamesFeatureCalledLegNameSet

Incremented when called leg name is found

Behaviour

Network pre-credit check

When invoked at the SipAccess_NetworkPreCreditCheck execution point the feature will do the following:

  • Retrieve the leg that the initial INVITE arrived on and get its name.

  • Set the CurrentCallingLegName session variable to the leg’s name.

  • On an originating instance, set the CurrentLocalLegName session variable to the leg’s name;
    on a terminating instance, set the CurrentRemoteLegName session variable to the leg’s name.

SIP access party response

When invoked at the SipAccess_PartyResponse execution point the feature will do the following:

  • Retrieve the leg that the response arrived on and get its name.

  • Verify that the response is to an INVITE and has a 2XX status. (If it isn’t, the feature will stop here.)

  • Set the CurrentCalledLegName session variable to the leg’s name.

  • On an originating instance, set the CurrentRemoteLegName session variable to the leg’s name;
    on a terminating instance, set the CurrentLocalLegName session variable to the leg’s name.

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Sentinel VoLTE Version 2.7.0