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

The policy and charging enforcement function (PCEF) of Junos Subscriber Aware enforces policy and charging control (PCC) rules for the treatment of a subscriber’s packets. A PCC rule is installed on, and enforced by, the PCEF. The PCC rules can be under static control, under dynamic control of the policy and charging rules function (PCRF), or under activation/deactivation control of a RADIUS server, depending on the PCEF profile that is assigned to a subscriber.

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.

Figure 1: Static Policy ControlStatic Policy Control

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.

Figure 2: Dynamic Policy ControlDynamic Policy Control

RADIUS Server Policy Control

For polices 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.

Figure 3: RADIUS Server Policy ControlRADIUS Server Policy Control