Question: What is the purpose of the Nudm_UECM_DeregistrationNotification service operation in the 5GS system?
Option 1: To register a new NF consumer with the UDM.
Option 2: To notify an NF consumer that it has been deregistered as a serving NF for a UE due to various reasons such as UE initial registration, subscription withdrawn, or SMF context transfer.
Option 3: To request a PDU session re-activation from the old SMF.
Option 4: To initiate a 5GS to EPS mobility procedure.
Explanation: The Nudm_UECM_DeregistrationNotification service operation is used by the UDM to notify an NF consumer that it has been deregistered as a serving NF for a UE. This notification is sent due to various reasons such as UE initial registration, subscription withdrawn, or SMF context transfer, indicating that the consumer is no longer registered in UDM as a serving NF for that UE.