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McKinney, TX (July 1, 2013) – The Policy Control and Charging (PCC) Rules Function (PCRF) is a centralized policy decision point that deploys business policy rules to allocate network resources and manages flow-based charges for subscribers and services.  Gx is the policy interface between the PCRF and the Policy and Charging Enforcement Function (PCEF), providing control over policy and flow-based charges for subscribers.

The Gx interface includes support for:

  • Service provisioning, activation, and deactivation;
  • Threshold triggers for service statistics processing;
  • Accounting;
  • Subscriber session  maintenance (activation, updating and termination);
  • Event notifications.

One important part of provisioning PCC rules is ascertaining that the requested resources associated with a PCC rule are successfully allocated.  The PCRF can request this verification from the PCEF with a CCA or RAR message that includes the Event-Trigger AVP with the value SUCCESSFUL_RESOURCE_ALLOCATION. The PCRF installs the rules that require resource allocation confirmation by including the Resource-Allocation-Notification AVP with the value ENABLE_NOTIFICATION within the corresponding Charging-Rule-Install AVP.

Developing Solutions’ dsTest supports this behavior of Policy Control by allowing a service to be configured with the ‘Resource_Allocation_Notification’ element.  See the dsTest schema for more information.

Reference: TS 29.212

Refer to the message flow below:

Message Exchange 1 (CCR-I/CCA-I): Initial Request and Answer

Initial Request and Answer

The PCEF establishes a Gx Session with the PCRF with a Credit-Control-Request Initialization (CCR-I) message.  The PCRF responds to the PCEF with a Credit-Control-Answer (CCA-I) in which the PCRF requests that the PCEF confirm that the resources associated with a PCC rule are successfully allocated.  This request by the PCRF is accomplished by the inclusion of an Event-Trigger AVP with the value of SUCCESSFUL_RESOURCE_ALLOCATION.


Message Exchange 2(AAR/AAA): Rx session established.

Gx Re-Authorization

The Call Session Control Function (CSCF) establishes a Rx Session with the PCRF with a Authorize/Authenticate-Request (AAR) message.  The PCRF responds to the CSCF with an AA-Answer (AAA).

Message Exchange 3 (RAR/RAA): Gx Re-Authorization

The establishment of a Rx session triggers a Gx Re-Authorization Request from the PCRF to the PCEF.

Using the Charging-Rule-Install AVP, the PCRF reauthorizes the installed PCC rules at the PCEF.  The PCRF indicates which rules require notification by including the Resource-Allocation-Notification AVP with a value of ENABLE_NOTIFICATION.

Message Exchange 4 (CCR-U/CCA-U): Gx Update

Gx Update

The RAR/RAA exchange triggers a Gx CCR Update (CCR-U) from the PCEF to the PCRF, based upon the initial CCR-I/CCA-I exchange with the Event-Trigger AVP with the value of SUCCESSFUL_RESOURCE_ALLOCATION from the PCRF (Message Exchange 1).  The PCEF includes the Charging-Rule-Report AVP in the CCR-U which contains the Charging-Rule-Name AVP for each of the rules installed.

Message Exchange 5/6/7 (STR/STA)/(RAR/RAA)/(CCR-T/CCA-T): Sessions are Terminated

The Rx session is terminated, resulting in a Gx reauthorization request/answer, and then the Gx session is terminated.


 About dsTest

dsTest originates, receives, and processes signaling traffic into and from the core network.  Multiple emulated nodes can be coordinated to simulate the UE traffic for complex signaling interactions such as VoLTE.  Unlike some test tools, dsTest provides stateful, standards-based applications that react appropriately to both expected and unexpected events without the need for scripting, simplifying the process of performance testing the signaling core.  dsTest provides multiple advanced testing features, such as SmartEventsDiameter Dictionary validation, and SmartAVP™ customized messages

dsTest surpasses all other tools with its capacity, its performance, and the ease with which you can customize the scenarios and messages to achieve your testing goals.

To learn more about Developing Solutions core network emulation and test solutions, refer to our product page or contact Developing Solutions, Inc. at or (877) 233-8350.

About Developing Solutions, Inc.

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Developing Solutions is a test equipment software development firm founded in 2002 with extensive experience in the Telecom and Datacom industries, including both NEM and test equipment manufacturers. Developing Solutions is located in the DFW Metroplex.