Section: 5.2.3.2.2 Nudm_UECM_DeregistrationNotification service operation
Content: Service operation name: Nudm_UECM_DeregistrationNotification. Description: UDM notifies the NF consumer which has previously registered (using Nudm_UECM_Registration operation) has been deregistered in the UDM. As a result, the consumer is no longer registered in UDM as a serving NF for that UE. NOTE: This notification corresponds to an implicit subscription. Inputs, Required: SUPI, Access Type, PDU Session ID, serving NF deregistration reason. Inputs, Optional: NF ID in the case of SM Context Transfer. Outputs, Required: None. Outputs, Optional: None. See step 14d of clauses 4.2.2.2.2 and 4.26.5.3 for an example usage of this service operation. The serving NF deregistration reason tells the reason for sending the deregistration notification to the consumer NF. The reason for AMF deregistration can be one of the following: - UE Initial Registration. - UE Registration area change. - Subscription Withdrawn. - 5GS to EPS Mobility. The reason for SMF deregistration can be one of the following: - SMF Context Transfer. - Removal of duplicated PDU Sessions in the old SMF. - PDU session being released requested to be re-activated. - Other UDM determined reason as specified in TS 29.503[ 5G System; Unified Data Management Services; Stage 3 ]  [52].