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5G Reference Network Architecture

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


5G Reference Network Architecture



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


5G Reference Network Architecture

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

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