Question: What happens when a Network Slice instance for an existing PDU Session is required to be changed due to congestion or unavailability?
Option 1: The AMF updates the old NSI ID corresponding to the congested or unavailable Network Slice instance.
Option 2: The SMF triggers the impacted UE(s) to release the PDU session without establishing a new one.
Option 3: The AMF deletes the old NSI ID and informs the SMF to release the PDU session, then the SMF triggers the impacted UE(s) to establish a new PDU session associated with the same S-NSSAI.
Option 4: The network changes the related network slice(s) for the UE without involving the AMF or SMF.
Explanation: When a Network Slice instance for an existing PDU Session is required to be changed, the AMF deletes the old NSI ID and informs the SMF to release the PDU session. The SMF then triggers the impacted UE(s) to establish a new PDU session associated with the same S-NSSAI, ensuring continuity of service. This process involves coordination between the AMF, SMF, and UE to ensure a seamless change of Network Slice instance.