You can use the Policy Enforcement Manager™ to implement quota management process for prepaid subscribers per session and per application. You can provision prepaid charging per subscriber or application that communicates with the quota protocol endpoint (QPE), such as online charging system (OCS), over the 3GPP Gy interface. The Gy endpoint allows online credit control for Layer 4 to 7 service data flow-based charging. This type of policing is called quota management; this feature ensures that subscribers do not consume resources that are not authorized. The Diameter Credit-Control Application (DCCA) specifies an approach based on a series of interrogations, that use Credit-Control-Request (CCR) and Credit-Control-Answer (CCA) messages.
If threshold for a Quota bucket is almost reached and the current flow 8KB interval is not used, then CCR-U is sent after 8KB consumption (maximum). PEM forwards it and after 8KB interval, or in between if in middle, it sends CCR-U. Consider 8KB consumption intervals when Quota bucket is being checked for exhaustion.
If larger bytes arrives between 8KB interval then it is let through. After we detect Quota is being exhausted, after usage of 8KB interval, then we update the internal policy change for the session. After reevaluation interval (20 seconds) the flow is reevaluated and then termination action is applied. However, for new flows as soon as Quota expires they are dropped.
The PCRF reports the quota usage under a number of circumstances and notifies the server through the use of the Reporting-Reason AVP in the CCR. The reason for reporting credit usage can occur directly in the Multiple-Services-Credit-Control AVP or in the Used-Service-Units AVP and depends on whether it applies for all quota types or a particular quota type.
The Gy interface in 3GPP architecture facilitates communication between the online charging system (OCS) and the PCEF. In turn, this communication supports the advanced credit authorization and quota-specific reporting. Policy Enforcement Manager™ provides online credit control, through user configuration, for Layer 4 to 7 service data flow-based charging.
The subscriber traffic contains consumed based on allocated quota that is based on applications, category, or a group of them and is measured in terms of volume, time, and events. A rating group, which is the same as a quota bucket, can be created. A rating group is identified by a service-identifier AVP that gathers a set of services, which has the same costs and rating type. Once you create a rating group, you can assign it to multiple rules inside the policy. For all the traffic matching the rule, quota is consumed from this bucket to make sure there is no over-subscription of resources. For example, you can have a rating group assigned to managing video traffic of 500 MB. This rating group needs to be assigned to a rule that matches the video traffic, to ensure that there is no over-subscription of subscriber video traffic.
Multiple Services Credit Control (MSCC) is a procedure that allows quota management for multiple services within one Gy Session. It is possible to allocate quota on a per service basis or the services can be grouped into rating group to gather aggregation of quota management. When the MSCC is present in the CCR message, it represents PCRF. The MSCC requests quota for a particular service, or multiple services, or usage being reported. When the MSCC is present in the CCA message, it represent OCS that grants quota for the service or services.
Online charging uses IETF Diameter Credit Control application. It uses the Gy reference point in the 3GPP standards for messages between the Online Charging Server and the PCEF. The PCEF requests resource allocation and reports credit control information to the OCS (Online Charging System). Event Charging with Unit Reservation (ECUR) using CCR Initial and Termination can be used to generate event messages.
The four Attribute Value Pair (AVP) that defines a rating group, are the amount of time, the downloaded, uploaded and total bytes.
|Terminate||The system stops traffic when quota is breached.|
|Allow||The system allows traffic to go through even when the quota is breached.|
|Redirect||The system redirects traffic to the forwarding endpoint, when quota is breached.|