The Policy Control Function, or PCF, is arguably one of the most important of the 5G Service-Based Architecture (SBA) Network Functions. It represents an evolution of the 4G Policy and Charging Rules Function (PCRF), which added capabilities to request and monitor service quality, on a per session basis. As well as retaining these session-based capabilities, the PCF adds additional functions, including control of network slicing, and new control mechanisms for UE activities, such as roaming and mobility management.
In the 5G Service-Based Architecture (SBA), the Policy Control Function (PCF) performs the same function as the Policy and Charging Rules Function (PCRF) does in 4G networks, but with additional functionality.
Arguably, the PCF is one of the most important of the 5G Network Functions, as policy and charging control will play a critical role in the evolving 5G ecosystem by providing visibility into and control over the use of differentiated network services in real time.
The PCRF is used in 4G / LTE networks to assist service data flow detection, policy enforcement, and flow-based charging, which ensures the reliable monitoring of services or use cases and the charges associated with each.
It also enables the reconfiguration of policies to effectively manage Quality of Service (QoS), charging, quota, optimisation, and admission control, and offers a number of benefits:
The 5G PCF, meanwhile, supports the unified policy framework that governs network behaviour by providing policy rules for control plane functions (such as network slicing, roaming and mobility management) and subscription information for the policy decisions taken, and by supporting new 5G QoS policy and charging control functions.
It builds on the PCRF by adding more functionality that enhances agility and flexibility in a dynamic, cloud-native environment. The main functions of the PCF include:
The PCF offers service providers multiple advantages, including efficient management of policies in a 5G network via an intuitive graphical interface; preparing the network to support massive IoT (mIoT) without compromising QoS; reducing network management costs; and enabling providers and MNOs to differentiate themselves with tailored offerings to consumer and enterprise customers.
As such, the PCF supports a unified policy framework within the 5G infrastructure for governing network behaviour. It uses the policy subscription information stored in the User Data Repository (UDR) to provide policy rules to network functions (SMF/AMF).
The PCF uses a standard REST-based interface to integrate with the AMF for access and mobility policy, and the SMF for session management policy. Interfaces supported by the PCF are described in numerous standards. For example, the interface with the SMF is covered in 3GPP TS 29.508, 5G System; Session Management Event Exposure Service, Stage 3.
However, of course, the migration towards 5G will not happen overnight, which creates two challenges:
What’s required is a cloud-native policy converged solution that can help service providers avoid multiple platform migrations and leapfrog the policy solution directly to the industry-defined 5G SBA. Having a secure and flexible policy converged solution is fundamental when seeking new revenue streams beyond connectivity and striving to take advantage of cloud-native technologies and 5G.
Emblasoft Evolver provides a comprehensive platform for validating Interworking functions. Not just for PCF use cases, but for any case that requires HTTP/2-based entities to connect with those that support Diameter, MAP and other legacy interfaces – in either direction and from the same platform, at the same time.
This flexibility helps solution providers and operators validate interworking scenarios, protect investments in legacy solutions and maximise return from new solutions added for 5G SA – in full public or private networks. Evolver enables:
To find out how Emblasoft Evolver can be used to successfully validate interworking between the new, 5G PCF and legacy network environments, including PCRF-enabled 4G networks, get in touch today.
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