This feature assists with originating sessions towards the Conference Factory by augmenting the REFER request sent from the UE to the Conference Factory .

The moderator UE sends a REFER request to add and remove conference participants. Such a REFER request contains a Refer-To header that is often re-written by Application Servers. The original value as sent by the UE is necessary for Re-INVITE based conferencing. This can be achieved through two means:

  1. copying the original value into a different header - the approach taken by this feature, or

  2. disabling any Application Server invocation for originating attempts towards the Conference Factory - the approach taken prior to introduction of this feature when re-INVITE based conference is used.

Feature cheat sheet

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



Originating only






Copies Refer-To header to X-MSW-Original-Refer-To

Prerequisite features

  • DetermineCallType

  • DetermineVoltePlanId

Network operator data

There is none.

Subscriber data

There is none.

Session input and output variables

Session input variables


Session output variables



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

Statistic Increments when…​

The feature is started.


Sentinel VoLTE encounters an error while attempting to start the feature.


A non-fatal problem is encountered and the feature and issues a warning.


A fatal problem is encountered and the feature cannot execute correctly.


The feature takes too long to complete and Sentinel VoLTE aborts execution.


The feature is triggered on a REFER request.


The REFER request contains a Refer-To header


This feature ignores any Trigger that is not a SIP REFER request. If the REFER request has a Refer-To header the feature copies the incoming Refer-To header into an outbound X-MSW-Original-Refer-To header.

This is to facilitate conference moderator Access Transfer where an originating SCC-AS must be present between the moderator UE and the call to the Conference Factory.

The rationale for this behaviour is that the Refer-To header tends to be re-written by routing B2BUA’s and the original value must be visible to the Conference Factory for re-INVITE based flows.

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Sentinel VoLTE Version 3.0.0