Question: When a PCEF includes `IMS_SIGNALLING` within the Bearer-Usage AVP in a CCR command for a default bearer dedicated to IMS signalling, how must the PCRF respond if it accepts this dedication?
Option 1: The PCRF shall include `IMS_SIGNALLING` within the Bearer-Usage AVP in the CCA command and apply the applicable QCI for IMS signalling, restricting the bearer's usage.
Option 2: The PCRF may choose to either include or exclude `IMS_SIGNALLING` from the Bearer-Usage AVP in the CCA command without any further restrictions.
Option 3: The PCRF must reject the request by not including `IMS_SIGNALLING` in the Bearer-Usage AVP and assigning a different QCI value not specified for IMS signalling.
Option 4: The PCRF will always deny the dedication of the default bearer to IMS signalling by excluding `IMS_SIGNALLING` from the Bearer-Usage AVP in the CCA command.
Explanation: This is because, according to specified behavior for PCC and QoS rule provisioning, when a PCEF indicates `IMS_SIGNALLING` for a default bearer and the PCRF accepts this, the PCRF must confirm this dedication by including `IMS_SIGNALLING` in its response (CCA command) and ensure the bearer is restricted to IMS signalling by applying the appropriate Quality Class Identifier (QCI) for IMS, maintaining service quality and integrity.