Do you know the characteristics of 5G core network (5GC)?

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3GPP defines the 5G core network as a decomposable network architecture, introducing a service-based interface (SBI) with HTTP/2 as the baseline communication protocol, and control plane and user plane separation (CUPS). This decomposition of 5G network function software, SBI, and CUPS are very supportive of cloud-native container-based implementations.

5GC network architecture (Source: Xianzao Classroom)

Although 5G network functions can be built based on traditional architectures (such as virtual machine-based monolithic architectures), only when 5G network functions (NFs) are designed and implemented on a cloud-native container-based microservice architecture can real innovations be achieved in terms of flexibility, high scalability, elasticity, simplified operations, and lifecycle management. So what are the characteristics of the 5G core (5GC)?

1. Separation of control and user planes

The 5G core network inherits the architecture of Control and User Plane Separation (CUPS) of 3GPP Release 14. In 4G EPC, S/PGW is decomposed into S/PGW-C and S/PGW-U, which independently provide efficient service extension.

This decomposition continues to 5G, with the user plane function (UPF) playing a role only in packet processing for user traffic, while all other single-point processing is done by other control plane functions such as the session management function (SMF). The CUPS architecture in the 5G core brings the advantages of cost savings and scalability by centralizing the control plane function (SMF) and distributing the user plane function (UPF) to edge data centers.

2. Stateless Architecture

3GPP standards introduced a stateless architecture to enable network optimization and better reliability and resilience.

Typically, a stateful network function/element must retain user information or contextual information associated with the transport layer, so when the function suddenly fails, this data must be preserved. Stateless architecture is a popular design pattern in modern microservices-based software architecture, which must use external data storage to decouple the application layer and data storage layer.

To this end, 3GPP defines the Unstructured Data Storage Function (UDSF) in TS 21.195.

3. Service-Based Interface (SBI)

The most significant change in the 5G core control plane is the introduction of a service-based interface (SBI) or service-based architecture (SBA) from the traditional point-to-point network architecture. With this new change, except for a few interfaces such as N2 and N4, almost every interface is now defined to use a unified interface, using the HTTP/2 protocol.

This change makes the communication between NFs more like a service mesh function rather than a serial link, which helps reduce the dependencies between each interface and facilitates the independent scaling of each function, and also improves the agility of having new features and services across network functions.

• Service-based architecture is based on a set of network functions (NFs)
• NF provides services to other NFs through Service Base Interface (SBI)
• The reference point interface has been replaced with a common bus connecting all NFs

4. Network Slicing

DECOR and eDECOR have been introduced in LTE/4G. With the maturity of network function virtualization (NFV) and software defined network (SDN) technologies, the practical application of cloud-native network architecture in 5G core will increase rapidly.

In 5G, network slicing is expected to enable enterprise customers to take advantage of networks that are "customized for specific customers or user characteristics" to meet every need for customizable network functions (such as speed, quality, latency, reliability, security and services). For network service providers, this will be a new opportunity to monetize network services.