The 5GC architecture relies on a “Service-Based Architecture” (SBA) framework, where the architecture elements are defined in terms of “Network Functions” (NFs) rather than by “traditional” Network Entities. Via interfaces of a common framework, any given NF offers its services to all the other authorized NFs and/or to any “consumers” that are permitted to make use of these provided services. Such an SBA approach offers modularity and reusability.
5G Core functions
5G Core follows the control and user plane separation (CUPS) strategy that was introduced in 3GPP Release 14. CUPS decouples control and user plane functions, enabling data forwarding components to be decentralized.
- User Plane Function (UPF) is responsible for packet processing and traffic aggregation of user traffic. Since this functionality is decoupled from the control component, it can be placed closer to the network edge near the end user or device, increasing bandwidth efficiencies and resulting in higher data rates and lower latencies.
- Access and Mobility Management Function (AMF) and Session Management Function (SMF) are part of the control plane. AMF is responsible for handling connections and mobility management tasks while SMF handles session management. AMF receives connection and session-related info from the end devices, passing the session info to SMF, which establishes sessions by using UPF.
- Policy Control Function (PCF) provides a framework for creating policies to be consumed by the other control plane network functions. Examples include policies for QoS, network slicing management, and subscribers, applications, and network resources management.
- Authentication Server Function (AUSF) provides authentication and Unified Data Management (UDM) ensuring user identification, authorization, and subscription management.
5G supplementary functions
- Network Repository Function (NRF) is used by AMF to select the correct SMF out of the available pool.
- NRF and Network Slice Selection Function (NSSF) work together to support network slicing capabilities.
- Network Exposure Function (NEF) exposes 5G services and resources so third-party apps can more securely access 5G services.
- Application Function (AF) exposes an application layer for interacting with 5G network resources, retrieving resource info from PCF, and exposing them.