Security Edge Protection Proxy(SEPP)

The User Plane Function (UPF) represents the data plane evolution of a Control and User Plane Separation (CUPS) strategy, which is a fundamental component of the 3GPP 5G core network(5GC).

The UPF plays the most critical role in the process of data transfer. It provides the interconnect point between the mobile infrastructure and the Data Network (DN), i.e. encapsulation and decapsulation of GTP-U.

NEF, located between the 5G core network and external third-party application functionaries (and possibly some internal AFs), is responsible for managing the external open network data, and all external applications that want to access the internal data of the 5G core must pass through the NEF.

By opening the network capability to third-party applications, it can realize the friendly connection between network capability and business requirements, improve business experience and optimize network resource allocation.

NRF, one of the network functions of the 5G core network(5GC). It supports the service discovery feature, which receives NF discovery requests from NF instances and provides information about the discovered NF instance (discovered) to another NF instance. Registration information includes NF type, address, service list, etc.

Network slicing is a key native capability of 5G that can maximize the performance of communication networks and reduce network construction and operation and maintenance costs, and it has become an industry consensus that 'slicing is capability and slicing is product' in the 5G era.
The core network, as a key anchor point for network differentiation and operation, has emerged as a more important network in the 5G era, providing the ability to deploy network functions and resources on-demand to meet the diverse business needs of future vertical industries.

UDM: The same as 4G’ s HSS (Home Subscriber Services), UDM is a centralized way to process network user data in 5G through Nudm interfaces to provide services for AMF, SMF, SMSF, AUSF, NEF and GMLC. It also provides services such as authorization of accessing, registration, uninterrupted services.

AUSF: As a major part of 5GC to facilitate security processes, AUSF performs the authentication function of identifying UEs and storing authentication keys.

The 5G PCF performs the same function as the PCRF in 4G networks.

• Provides policy rules for control plane functions. This includes network slicing, roaming and mobility management.
• Accesses subscription information for policy decisions taken by the UDR.
• Supports the new 5G QoS policy and charging control functions.

SMF is a fundamental element of the 5G Service-Based Architecture (SBA). The SMF keeps trace of PDU sessions and QoS Flows in the 5GC for UEs and make sure their states and status are in sync between Network Functions in Control and User Planes.
It also receives PCC (Policy and Charging Control) Rules from PCF (Policy Charging Function) and convert PCC Rules into SDF Templates, QoS Profiles and QoS Rules for UPF, gNB and UE respectively for QoS Flows establishment, modification and release etc.

AMF terminates the control plane of different access networks onto the 5G Core Network(5GC) and control which UEs can access the 5GC to exchange traffic with DNs. It also manages the mobility of UEs when they roam from one gNB to another for session continuity, whenever possible.

N3IWF (Non-3GPP InterWorking Function) is responsible for connecting untrusted non-3GPP access network to 5GC. UE and N3IWF establish an IPSec tunnel, N3IWF connects to the User Plane and Control Plane of 5GC through N2 interface and N3 interface separately.