What is PCF?
The PCF is the 5G Core network function providing a unified policy framework. It generates and delivers policy rules — covering QoS, charging triggers, traffic steering, and access control — to the AMF (for access and mobility policy), SMF (for session and QoS policy), and indirectly to the RAN (via the AMF for radio policy).
How Does PCF Work?
The PCF retrieves subscriber policy data from the UDM and applies operator-configured rules. It exposes the Npcf service interface. For each PDU session, the PCF provides the SMF with PCC (Policy and Charging Control) rules that define QoS flows, data rate limits, and charging methods. It can dynamically update policies in response to real-time events via the N5 interface from Application Functions (via the NEF).
Use Cases
Enforcing subscriber data plan limits, applying QoS guarantees for network slice SLAs, enabling dynamic congestion management, third-party application QoS requests (e.g. video streaming priority), roaming policy enforcement.
3GPP / Standards Reference
3GPP TS 29.507 (Npcf Service Definition), TS 23.503 (Policy and Charging Control Framework)
Related Terms
SMF | AMF | UDM | NEF | QoS | Network Slicing
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