The Policy Control and Charging (PCC) Rules Function (PCRF) is a centralized policy decision point that provides dynamic policy management and deploys business policy rules to allocate and monitor network resources and manage flow-based charges for subscribers and services. Gx is the policy interface between the PCRF and the Policy and Charging Enforcement Function (PCEF) that provides this control.
An important part of provisioning PCC profiles for subscribers is the ability to monitor usage of network resources during an IP-CAN session. Usage can be volume or time, which can be performed in parallel. Usage monitoring and reporting can be by individual PCC rule or for an entire IP-CAN session.
Developing Solutions’ dsTest supports this behavior of Policy Control by allowing a subscriber’s PCC profile to be configured with the ‘usage_monitoring’ element and its sub-elements. dsTest users can test a full range of usage monitoring and reporting scenarios. See the dsTest schema for more information.
Usage Monitoring and Reporting
3GPP TS 29.212 specifies how Usage Monitoring and Reporting is to be provided over the Gx interface.
In general, usage monitoring and reporting can be requested by the PCRF with a CCA, RAR, or RAA message. Usage monitoring can be requested on an individual rule (PCC rule level) or on all rules activated during a IP-CAN session (session level).
Each data set, other than session level, that is to be monitored has an associated monitoring “key”. The PCRF specifies the data to be reported by including the usage monitoring key for each set of data being monitored within a Monitoring-Key AVP within the Usage-Monitoring-Information AVP. The PCRF can request all enabled usage monitoring (that is, session level) by omitting the Monitoring-Key AVP.
Refer to the message flow below:
Message Exchange 1 (CCR-I/CCA-I): Initial Request and Answer
An IP-CAN session is established by an exchange of Credit Control Request (CCR-I) and Credit Control Answer (CCA-I) messages between the PCEF and the PCRF.
Figure 1-1
In responding to the CCR-I, the PCRF sends a CCA-I that specifies the monitoring key for each data set for which it wants to enable usage monitoring. To request usage reporting for all enabled monitoring keys (the entire session), the Monitoring-Key AVP is omitted. See Figure 1-1 for an example of the Usage-Monitoring-Information AVP with a Monitoring-Key AVP (PCC rule level) and Figure 1-2 for an example without a Monitoring-Key AVP (session level).
The PCRF requests the PCEF to report usage by including the Usage-Monitoring-Report AVP (in the Usage-Monitoring-Information AVP) set to USAGE_MONITORING_REPORT_REQUIRED in the CCA-I message.
Figure 1-2
Refer to the Diameter Dictionary for a description of the other AVPs that can be included in the Usage-Monitoring-Information AVP.
Rules, installed by the PCRF via the Charging-Rule-Install AVP, are assocated with data sets being monitored by including the Monitoring-Key AVP in the Charging-Rule-Install AVP.
Message Exchange 2 (RAR/RAA) PCC Rule Install
The PCRF can also install rules using a Re-Authorization Request (RAR) message and request usage monitoring for those rules. If monitoring is requested for a rule, the RAR will contain a Usage-Monitoring-Information AVP for each monitoring key, and the desired threshold levels are provided in a Granted-Service-Unit AVP.
The RAR Usage-Monitoring-Information AVP:
Figure 2-1
- Monitoring-Key AVP specifying the monitoring key associated with the rule being installed;
- Granted-Service-Unit AVP with
- CC-Total-Octets AVP;
- CC-Input-Octets AVP;
- CC-Output-Octets AVP;
- Usage-Monitoring-Level AVP set to PCC_RULE_LEVEL;
- Usage-Monitoring-Report AVP with a value of USAGE_MONITORING_REPORT_REQUIRED.
Refer to Figure 2-1.
As with the CCA-I message above, the rule is installed via the Charging-Rule-Install AVP:
Figure 2-2
- Charging-Rule-Name AVP;
- Monitoring-Key AVP that corresponds to the monitoring key specified in the Usage-Monitoring-Information AVP.
Refer to Figure 2-2.
Message Exchange 3 (RAR/RAA): PCC Rule Remove
Later, the rule installed in Message Exchange 2 is removed with another RAR/RAA exchange. This rule remove action triggers an update request from the PCEF. See the CCR-U/CCA-U exchange in Message Exchange 4.
Message Exchange 4 (CCR-U/CCA-U): Update
When the PCRF removes a rule via a RAR, it also disables usage monitoring associated with that rule. The PCEF sends a CCR-U with CC-Request-Type AVP set to “UPDATE_REQUEST” and the Event-Trigger AVP set to “USAGE_REPORT” to report accumulated usage for the disabled usage monitoring key(s). Refer to Figure 4-1
- Event-Trigger AVP with value of USAGE-REPORT;
Figure 4-1
- Usage-Monitoring-Information AVP with:
- Monitoring-Key AVP that contains the same monitoring key that was specified in the RAR/Rule Install;
- Used-Service-Unit AVP with:
- CC-Total-Octets AVP;
- CC-Input-Octets AVP;
- CC-Output-Octets AVP.
Message Exchange 5 (CCR-U/CCA-U)
The PCEF can send update requests independent of usage monitoring and reporting.
Message Exchange 6 CCR-T/CCA-T: IP-CAN Session is Terminated
When a IP-CAN session is terminated, the PCEF reports accumulated usage for a specific monitoring key by sending a CCR-T with the Usage-Monitoring-Information AVP which includes a:
- Monitoring-Key AVP;
Figure 6-1
- The accumulated usage since the last report in the form of the Used-Service-Unit AVP with:
- CC-Total-Octets AVP;
- CC-Input-Octets AVP;
- CC-Output-Octets AVP.
For More Information
For more information on this Use Case, including the dsTest configuration files and message trace file used to create this Use Case, contact Developing Solutions at (877) 233-8350 or info@developingsolutions.com.
Other dsTest Resources and Features
- dsTest Products;
- dsAnalyzer – analyze your Diameter and GTP message traces;
- SmartEvents – This Use Case was prepared using dsTest and dsClient GUI, configured with SmartEvents on both the PCEF and the PCRF;
- SmartAVP – Custom AVPs can be added, AVPs can be removed or modified in real time;
- dsClient GUI – A graphical user interface for configuring and running dsTest;
- SmartAVP Extract – Extract information from AVPs.