5G Reference Network Architecture

5G Reference Network Architecture - as per 3GPP TR 23.799

1. Network nodes and their functions:

• User Equipment (UE)
• Next Gen Node Basestation (gNB)

2. Core Access and Mobility Management Function (AMF) – responsible for following:

• Termination of RAN Control Plane interface (NG2)
• Termination of NAS (NG1), NAS ciphering and integrity protection
• Mobility Management
• Lawful intercept (for AMF events and interface to Lawful Inetercept System)
• Transparent proxy for routing access authentication and SM messages
• Access Authentication
• Access Authorization
• Security Anchor Function (SEA): It interacts with the UDM and the UE, receives the intermediate key that was established as a result of the UE authentication process; in case of USIM based authentication, the AMF retrieves the security material from the UDM
• Security Context Management (SCM): it receives a key from the SEA that it uses to derive access-network specific keys

3. User plane Function (UPF) – functions are:

• QoS handling for User plane
• Packet routing & forwarding
• Packet inspection and Policy rule enforcement
• Lawful intercept (User Plane)
• Traffic accounting and reporting
• Anchor point for Intra-/Inter-RAT mobility (when applicable)
• Support for interaction with external DN for transport of signaling for PDU session authorization/authentication by external DN

4. Session Management Control Function (SMF) – supports following:

• Session Management
• UE IP address allocation & management (including optional Authorization)
• Selection and control of User Plane function
• Termination of interfaces towards Policy control and Charging functions
• Control part of policy enforcement and QoS
• Lawful intercept (for Session Management events and interface to Lawful Intercept System)
• Termination of Session Management parts of NAS messages
• Downlink Data Notification
• Initiator of Access Node specific Session Management information, sent via AMF over NG2 to Access Node
• Roaming functionality
• Handle local enforcement to apply QoS SLAs (VPLMN)
• Charging data collection and charging interface (VPLMN)
• Lawful intercept (in VPLMN for Session Management events and interface to Lawful Intercept System)
• Data Network (DN): Operator services, Internet access or other services

5. Authentication Server Function (AUSF) 

• Performs authentication processes with the UE
• Unified Data Management (UDM) – Supports:
• Authentication Credential Repository and Processing Function (ARPF); this function stores the long-term security credentials used in authentication for AKA
• Storing of Subscription information

6. Policy Control Function (PCF)  Provides:

• Support of unified policy framework to govern network behavior
• Policy rules to control plane function(s) that enforce them

7. Application Function (AF) 

• Requests dynamic policies and/or charging control