, and PCF Subscribe AF, NEF, NWDAF, and PCF Unsubscribe AF, NEF, NWDAF, and PCF Npcf_SMPolicyControl Create Request/Response UpdateNotify Subscribe/Notify Update Request/Response Delete Request/Response Npcf_BDTPolicyControl Create Request/Response Update Request/Response Notify Npcf_UEPolicyControl Create Request/Response AMF and V-PCF Update Request/Response AMF and V-PCF UpdateNotify Subscribe/Notify AMF and V-PCF Delete Request/Response AMF and V-PCF Npcf_EventExposure Subscribe Subscribe/Notify NEF and NWDAF Unsubscribe Notify Figure 3.18 - Services offered by the PCF The Npcf_BDTPolicyControl service allows the creation and updation of a background data transfer policy, based on requests from consumers such as the AF and NEF. The Npcf_UEPolicyControl service allows the service consumer, such as the AMF, to create, update, and delete UE policy associations. When a policy control request trigger condition is met, the consumer can contact the PCF to inform it about the trigger condition being met. Similarly, the AMF can also use this service to notify the PCF to update the UE policy when certain conditions of events have been met to trigger in a similar way - for example, AMF relocation. REST in 5G The Npcf_EventExposure service is used by a consumer to subscribe and be notified of certain events taking place in the PCF. NEF services The NEF provides services to its consumers' AF, the NWDAF, and SMF consumers, per 3GPP Release 16, 23.502: The Nnef_EventExposure service, hosted by the NEF, is used by the NWDAF to collect data from the AF. The NWDAF subscribes to events, and the event IDs are associated with the data in the AF and exposed by the NEF. The Nnef_PFDManagement service is used by consumers such as the SMF and AF to create, update, and remove packet flow descriptions. Service Name Service Operations Semantics Consumer(s) Service Name2 Service Operations2 Semantics2 Example Nnef_EventExposure Subscribe Subscribe/Notify AF, NWDAF Nnef_AFsessionWithQoS Create Request/Response unsubscribe AF, NWDAF Notify