System architecture

References points representation.

• shows the interaction that exists between the NF services in the network.

• functions described by point-to-point reference points (e.g. N11).

• between any two network functions (e.g. AMF and SMF).

Service-based representation where network functions (e.g. AMF) within the control plane enable other authorized network functions to access their services.

Network Functions are self-contained, independent, and reusable. Each Network Function service exposes and makes available its functionality (services) through a Service Based Interface (SBI), which employs a well-defined REST interface using HTTP/2.

AMF, SMF and PCF

Access and Mobility Management Function (AMF).

• Termination of NAS signaling.

• NAS ciphering & integrity protection.

• Registration management.

• Connection management.

• Mobility management.

• Access authentication and authorization.

• Security context management.

Session Management Function (SMF).

• Session management (establishment, modification, release).

• UE IP address allocation & management.

• UPF selection and configuration for QoS and traffic steering.

• DHCP functions.

• Lawful intercept functions.

• Charging data collection and support of charging interfaces.

Policy Control Function (PCF).

• Supports unified policy framework to govern network behavior.

• Provides policy rules to Control Plane function(s) to enforce them.

• Accesses subscription information relevant to policy decisions in a Unified Data Repository (UDR).

AUSF and UDM

Authentication Server Function (AUSF).

• Acts as an authentication server for 3GPP access and untrusted non-3GPP access.

Unified Data Management (UDM).

• Generation of 3GPP Authentication and Key Agreement (AKA) credentials.

  • User Identification handling.

  • Access authorization based on subscription data.

  • Lawful Intercept functionality.

  • Subscription management.

NEF, NRF and NSSF

Network Slice Selection Function (NSSF).

• Selecting of the Network Slice instances serving the UE.

• Selecting of the Network Slice instances serving the UE.

• Determining the AMF set to be used to serve the UE.

Network Exposure function (NEF).

• Exposure of capabilities and events.

• Secure provision of information from external application to 3GPP network.

• Translation of internal/external information.

NF Repository function (NRF).

• Supports service discovery function.

• Maintains the NF profile of available NF instances and their supported services.

UPF

User Plane Function (UPF).

• Packet routing & forwarding.

• Anchor point for Intra-/Inter-RAT mobility.

• External PDU session point of interconnect to Data Network.

• Packet inspection and User plane part of Policy rule enforcement.

• Lawful intercept (UP collection).

• Traffic usage reporting.

• Uplink classifier (ULCL) to support routing traffic flows to a data network.

• QoS handling for user plane, e.g. packet filtering, gating, UL/DL rate enforcement.

• Transport level packet marking in the uplink and downlink.

• Downlink packet buffering and downlink data notification triggering.

AF and DN

Application Function (AF).

• Application influence on traffic routing.

• Accessing Network Exposure Function.

• Interacting with the Policy framework for policy control.

Data Network (DN).

• Operator services.

• Internet access.

• 3rd party services.

• May be a Local Area Data Network (LADN):

  • a DN that is accessible by the UE only in specific locations, that provides connectivity to a specific Data Network Name (DNN), and whose availability is provided to the UE.

Data storage

Unstructured Data Storage Function (UDSF).

Unified Data Repository (UDR).