Policy Management

Description

Policy management is a fundamental concept in 3GPP networks, introduced in Release 5. It refers to the capability to create, modify, and delete policy-related information, including policy events. This encompasses the lifecycle management of policies that govern various aspects of network behavior, such as QoS, charging, access control, and mobility. Policy management is essential for operators to enforce business rules, optimize network resources, and deliver differentiated services to subscribers.

In the 3GPP architecture, policy management is primarily handled by the Policy and Charging Rules Function (PCRF) in 4G and the Policy Control Function (PCF) in 5G. These functions interact with other network elements, such as the PCEF (Policy and Charging Enforcement Function) in the gateway, the AF (Application Function), and the SPR/UDR (Subscription Profile Repository/Unified Data Repository), to obtain subscription data, service information, and network conditions. Based on these inputs, the PCRF/PCF makes policy decisions and installs or modifies PCC rules in the PCEF. Policy management also includes the management of policy events, which are triggers that cause the PCRF/PCF to re-evaluate policies, such as changes in subscriber location, usage thresholds, or time of day.

The process of policy management involves several steps. First, policies are provisioned or created, either statically by the operator or dynamically based on subscriber actions or network events. These policies are stored in the PCRF/PCF or in an external repository. When a session is established or modified, the PCRF/PCF evaluates the applicable policies and generates PCC rules. These rules are then enforced by the PCEF, which may be in the PGW (Packet Data Network Gateway) or SMF (Session Management Function) in 5G. Policy management also includes the ability to modify or delete policies when they are no longer needed or when conditions change. For example, if a subscriber exceeds their data quota, the policy might be modified to reduce QoS or block access.

Policy events are a key part of policy management. They represent specific occurrences that trigger policy decisions. Examples include the start or end of a session, changes in subscriber location, changes in usage, or the expiration of a time-based policy. The PCRF/PCF can subscribe to these events from other network functions, such as the OCS/CHF for spending limits or the AF for service information. When an event occurs, the PCRF/PCF re-evaluates the policies and may update the PCC rules accordingly. This dynamic behavior ensures that policies remain relevant and effective in real-time.

In Release 16, the definition of policy management was updated to a more general statement: 'A function that governs the choices in behaviour of a system.' This broader definition reflects the evolution of policy management beyond just PCRF/PCF to encompass a wider range of systems and technologies, including network slicing, edge computing, and IoT. It emphasizes that policy management is about governing system behavior through policies, which can be applied in various contexts. Despite the wording change, the core concept remains the same: policy management is the set of capabilities to manage policies that control network behavior.

Overall, policy management is a critical enabler for flexible, dynamic, and efficient network operations. It allows operators to implement complex business rules, ensure fair usage, and provide personalized services. As networks evolve towards 5G and beyond, policy management continues to play a central role in orchestrating network resources and delivering value-added services.

Purpose & Motivation

Policy management was introduced to address the need for dynamic and flexible control of network behavior based on operator-defined policies. Before its introduction, network behavior was largely static, determined by subscription data and pre-configured settings. This limited the ability to adapt to changing conditions, such as network congestion, subscriber usage, or service requirements. Policy management provides a framework to create, modify, and delete policies that govern various aspects of network behavior, enabling operators to enforce business rules and optimize resource usage.

The concept solves the problem of integrating multiple sources of information (subscription, service, network) into a coherent policy decision. It allows the PCRF/PCF to act as a central decision point, gathering inputs from various network functions and making policy decisions that are enforced by the PCEF. This centralized approach simplifies the management of policies and ensures consistency across the network. It also enables real-time policy adjustments based on events, such as spending limits or location changes, which is essential for prepaid services and dynamic QoS.

Over time, policy management has evolved to encompass a broader scope. The Release 16 definition change reflects the expansion of policy management to govern the behavior of any system, not just the PCRF/PCF. This aligns with the trend towards softwarization and programmability in networks, where policies are used to control a wide range of functions, including network slicing, edge computing, and IoT. The purpose remains to provide a flexible and scalable mechanism for controlling network behavior, but the application domain has widened. Policy management is now seen as a key enabler for automation and orchestration in 5G and beyond.