By Peter Cohen
The 3GPP has defined a Service Based Architecture (SBA) for the 5G Core. Services are the essential building blocks used to create and execute the functions of a mobile network. The SBA delivers core network services as a set of interconnected Network Functions (NFs) which communicate with each other via a Service Based Interface (SBI). Each NF is containerized and operates independently, and exposes its functionality to other NFs through a SBI.
As the 3GPP explains, “That means wherever suitable the architecture elements are defined as network functions that offer their services via interfaces of a common framework to any network functions that are permitted to make use of these provided services.”
Network Functions (NF) in a Service Based Architecture
The Service Based Architecture of the 5G Core is a flat architecture that separates Control Plane (CP) functions from User Plane (UP) functions. The SBA infrastructure is fundamentally different from the Point to Point (P2P) model that preceded it because NFs exist independently and autonomously from one another rather than requiring dependencies that take time and personnel to maintain and optimize.
NFs in the SBA manage authentication and security, session management, and traffic aggregation. 5G Core NFs include the Authentication Server Function (AUSF), used to validate User Equipment (EU); Network Exposure Function (NEF), a service discovery feature; Network Repository Function (NRF), which profiles NFs functionality; Network Slice Selection Function (NSSF), which selects the optimal network slice available; and more.
Service Based Architecture: Essential for 5G
While enhanced broadband speeds and better reliability are hallmarks of 5G, the real meat of the new standard lies in innovations like ultra-reliable low latency communications (URLLC), massive machine-type communication (mMTC), mobile edge computing (MEC) and network slicing – the ability to create logical slices of network functionality optimized for different service characteristics, all operating on a common physical network – are only possible once telcos migrate to a standalone 5G core network.
This cloud-native approach builds on web technology fundamentals. It enables telcos to deliver services reliably, securely, and more efficiently to demanding enterprise customers, tailored specifically to their varying service needs. The 5G Core’s SBA enables Network Function Virtualization (NFV) and Software Defined Networking (SDN) to happen at scale.
4G vs. 5G network architecture
The central backbone of a 4G LTE network is the Evolved Packet Core (EPC). UP data is separated from CP data at the base station; both are fed independently into the EPC. This type of architecture creates bottlenecks and limitations, making the high speed, low latency, and machine to machine communication which are cornerstones of 5G impossible.
The Service Based Architecture of the 5G Core replaces the more monolithic EPC with network functions that can operate independently from one another and are free from hardware dependencies, so telcos have more freedom in which vendors and hardware they want to use.
According to Nokia, “The shift to a 5G SA core also requires adopting a service-based architecture (SBA), because the traditional peer-to-peer (P2P) network architectures that served CSPs for basic consumer voice, data and messaging services are rigid and struggle with scaling, redundancy and extensibility for rapid service innovation.”
The Service Based Architecture of the 5G Standalone (SA) core enables telcos to scale networks and services more efficiently, improves resilience and unlocks new functionality to support the myriad needs of enterprises and end users who are migrating to 5G.
