Section: 4.4.1.2 N4 Session Establishment procedure
Content: The N4 Session Establishment procedure is used to create the initial N4 session context for a PDU Session at the UPF. The SMF assigns a new N4 Session ID and provides it to the UPF. The N4 Session ID is stored by both entities and used to identify the N4 session context during their interaction. The SMF also stores the relation between the N4 Session ID and PDU Session for a UE. Figure 4.4.1.2-1 N4 Session Establishment procedure 1. SMF receives the trigger to establish a new PDU Session or change the UPF for an established PDU Session. 2. The SMF sends an N4 session establishment request message to the UPF that contains the structured control information which defines how the UPF needs to behave. 3. The UPF responds with an N4 session establishment response message containing any information that the UPF has to provide to the SMF in response to the control information received. If the UPF (by configuration or other means) utilizes an NWDAF, UPF adds the NWDAF serving the UE identified by the NWDAF instance ID. Per NWDAF service instance the Analytics ID(s) are also included. NOTE: The SMF can use this NWDAF related information and can forward it to the PCF using the SMF initiated SM Policy Modification procedure, as a result of a Policy Control Request Trigger. 4. The SMF interacts with the network function which triggered this procedure (e.g. AMF or PCF).