5G Core Network

5GC = 5G Core Network

The traditional network is mainly constructed for the communication demands between people and people. With the massive demands of the vertical industriesy ofof Internet of Everything (IoE),  the process architecture of the  binding traditional network binding software with hardware and the solidifying process architecture  between the network entities s can no longer meet suchthe requirements. To address these new business demands, 5G Core network relies on the core idea of Cloud Native, through theuses service-based network ararchitecture (SBA), network resources can be sliced slicing, and CUPScontrol plane and user plane are separated, . Iin combination with cloud technology, to achieve a customized, exposingopen, and service-based network is achieved.
5G core networkCore has been reconstructed to redefine the network entityties in the form of Network Function (NF). Each NF provides functions by independent functions (services) and can be called from each other, thus achieving the transition from a traditional rigid network (fixed functions of network elements, fixed connections between network elements, solidified signaling interactions) to a service-based flexible network.

Figure 1 3GPP Service-based Architecture 

Generally speaking, 5G SBA Core has the following key features:
Decoupled and service-based NFs
NFs that make up the core network are decoupled/divided at the functional level, and NFs are divided into several self-contained, self-managed, reusable network function services (NFS). They can operate independently without relying on each other. NFS can be upgraded and scale in/out independently. NFS provides service-based standardize interfaces to facilitate communication with other NFS.
Automatic network operation
Similar to the SOA/MicroService architecture concept in the IT Domain, 5G Core introduces a new network function entity (NRF), which provides functions such as NF service registration management, and NF service discovery mechanisms. As a consumer, NF only needs to find the applicable target NF/NFS through NRF. The core network is automated through this service mechanism so that the NF instance or NFS can be plug-and-play.
On-demand network slicing
NFs in the core network can serve different slices (shared slices) or a specific slice service (a specified slice). The NSSF in the 5G Core provides slice selection service. Different applications can use different slice network resources according to slice requirements to meet service requirements.
Secure mutual access of NF/NFS
NFs under the 5G SBA can automatically register to the NRF as function service providers, and any NF entity can obtain and use a service by initiating a service request to the NRF. To ensure network security, 3GPP defines security-related specifications (such as 33501), restricting the use of network functions only to authenticated or secure entities. The access security assurance methods are as follows:
NRF authentication function 
A security access rule is configured on the NRF side. When the initiator NF initiates a service request to the NRF, the NRF determines whether the request can be authorized according to the rule. The NRF returns the target NF related information only after the authorization.
NRF oAuth authorization function
NRF, which is regarded as the authorization server, provides the oAuth authorization service. The service provider needs to pass the NRF authentication and exchange certificates. The initiator NF needs to obtain the dynamic token from the NRF at first, and then bring the token to call the service from the target NF. The target NF determines that the token is legally valid before providing the service.
In summary, 5G Core based on SBA is a major innovation in the next-generation network architecture. It has the advantages that are not available in traditional networks such as flexible and open, and it is an important basis for quickly meeting the needs of various industries. With the large-scale deployment and commercialization of 5G networks, on the basis of 5G networks, applications based on the Internet of Everything will inevitably emerge.