Understanding Junos Subscriber Aware Policy and Charging Enforcement Function (PCEF)

Static Policy Control

For static policies, the PCEF enforces PCC rules you predefined on the MX Series router with no interaction from the PCRF or a RADIUS server, as shown in Figure 1.

Dynamic Policy Control

For dynamic policies, the PCEF acts upon messages received from the PCRF. The PCRF is the central entity that makes policy and charging decisions based on input from different sources, such as mobile operator configuration, user subscription information, and services information. The PCC rules are either provisioned by the PCRF and sent to the PCEF over the Gx interface using Diameter AVPs, or predefined on the MX Series router and activated by a Diameter message from the PCRF. The PCEF also provides the PCRF with subscriber and access information. See Figure 2.

When PCC rules are under dynamic control, the PCEF gives precedence to rules sent by the PCRF over rules that are predefined on the PCEF.

RADIUS Server Policy Control

For policies under control of a RADIUS server, a RADIUS server activates and deactivates policy and PCC rules that you have predefined on the MX Series router, as shown in Figure 3.

A PCEF profile with RADIUS server control requires an AAA profile, which provides the policy control attributes for RADIUS servers. Subscription-Id-Data in CCR is sourced from the RADIUS server and Calling-Station-Id is received with RADIUS requests.

Usage monitoring is supported through the Third Generation Partnership Project (3GPP) with Gx profile for subscriber services using the dynamic-profile configuration.