Section: 4.4.1.3 N4 Session Modification procedure
Content: The N4 Session Modification procedure is used to update the N4 session context of an existing PDU Session at the UPF, which is executed between SMF and UPF whenever PDU Session related parameters have to be modified. Figure 4.4.1.3-1 N4 Session Modification procedure 1. SMF receives the trigger to modify the existing PDU Session. 2. The SMF sends an N4 session modification request message to the UPF that contains the update for the structured control information which defines how the UPF needs to behave. 3. The UPF identifies the N4 session context to be modified by the N4 Session ID. Then, the UPF updates the parameters of this N4 session context according to the list of parameters sent by the SMF. The UPF responds with an N4 session modification response message containing any information that the UPF has to provide to the SMF in response to the control information received. 4. The SMF interacts with the network entity which triggered this procedure (e.g. AMF or PCF).