Section: 4.4.3.4 N4 Report Procedure
Content: The N4 Report procedure shall be used by the UPF to report information to the SMF which is not related to a specific N4 session, e.g. to report a user plane path failure affecting all the N4 sessions towards a remote GTP-U peer. N4 Report procedure can be used by the UPF to report the clock drift between the external time and 5GS time for one or more external working domains as specified in TS 29.244[ Interface between the Control Plane and the User Plane nodes ]  [69]. Figure 4.4.3.4-1: N4 report procedure The UPF detects that an event has to be reported and starts the procedure by sending an N4 Report message (UPF ID, list of [event, status]) to the SMF. The SMF responds with an N4 report ACK message (SMF ID). The event parameter contains the name of the event and UPF ID. The status parameter contains the actual information the control plane function is interested in. If the UPF detects clock drifting between 5G time and one or more time working domains, the UPF reports the corresponding external domain number and the time offset and cumulative rate Ratio according to the provisioning from the SMF as defined in clause 5.27.2 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2]. The UPF includes the Network Instance (if available) and the combination of DNN and S-NSSAI (if available) in the report. NOTE: When the UPF supports more than one NW-TT, the SMF can use the Network Instance or DNN/S-NSSAI to associate the report with the corresponding N4 sessions and NW-TT.