How it Works

This section describes how this feature works.

At a high-level, PCF supports the Rx-based authorization of bearers. The Rx authorization requires a Search Table Groups (STG), which enables logical grouping of multiple Customer Reference Data (CRD) tables. Within this STG, a CRD table that is dedicated to Rx Authorization is created in the Policy Builder. The input keys in the CRD signify the conditions based on which PCF determines the throttle limit for a bearer. The table has the following output columns:

  • Bearer Authorization: Indicates whether to allow or reject a bearer.

  • Error Cause: Specifies the Error-Message that is included in the AAA Diameter message, if necessary.

If PCF is configured to reject the Rx dedicated bearer when the associated Media-Type is missing, it rejects the bearer with the Experimental-Result-Code=INVALID_SERVICE_INFORMATION (5061) in AAA.

PCF is configured to reject a non-GBR bearer if the value for both, upload and download of the non-GBR bearer is set to 0. PCF determines if the bearer is non-GBR with 0-bit rate after consulting the NON-GBR QCI and ZERO BIT RATE QoS input columns in the Rx Authorization table. If PCF rejects the bearer, then its Bearer-Authorization value is set to REJECT with Result-Code=DIAMETER_AUTHORIZATION_REJECTED (5003) AVP and the Error-Message="BLOCKED (0)" in AAA.

If PCF receives an AAR message with multiple Media-Component-Descriptions AVPs, and it rejects one of the AVPs after assessing for Rx Authorization. PCF sends a successful AAA message for the accepted AVPs. For the rejected media component, PCF creates a scheduled event for sending a delayed Rx RAR. You can configure the duration between the rejection and the time when scheduling of the delayed message happens. The default value is set to 500 milliseconds.

Note

In case PCF rejects multiple Media-Component-Descriptions AVPs with AAA 5003, the Error-Message resulting from the last evaluated rejected AVP is sent in the AAA message.

For existing bearers in an Rx session, PCF evaluates them for Rx Authorization when an event occurs such as LDAP refresh, N28 NOTIFY, and N7_NOTIFY. In situations where all the Media-Component-Descriptions that are stored in the Rx sessions are rejected, then PCF sends an Rx Abort-Session-Request (ASR) to Application Function (AF).

Note

You may observe a degradation in the performance of the PCF system when the RxAuthorizationSTGConfiguration service is added. The level of degradation corresponds to the number of STGs configured for the chained evaluation in the RxAuthorizationSTGConfiguration service and the number of bearers the service has evaluated.