Access network node, user equipment, network function node and control method

A method performed by a User equipment (UE), the method comprising:

• transmitting, to an Access and Mobility Management Function (AMF), a first message comprising both a Single-Network Slice Selection Assistance Information (S-NSSAI) for a Protocol Data Unit (PDU) session and an Alternative S-NSSAI for the PDU session;
• and
• receiving, from the AMF, a second message comprising the Alternative S-NSSAI for the PDU session based on a determination to replace the S-NSSAI for the PDU session with the Alternative S-NSSAI for the PDU session, the determination being performed by the AMF based on the first message.

A method performed by an Access and Mobility Management Function (AMF), the method comprising:

• receiving, from a User Equipment (UE), a first message comprising both a Single-Network Slice Selection Assistance Information (S-NSSAI) for a Protocol Data Unit (PDU) session and an Alternative S-NSSAI for the PDU session;
• and
• transmitting, to the UE, a second message comprising the Alternative S-NSSAI for the PDU session based on a determination to replace the S-NSSAI for the PDU session with the Alternative S-NSSAI for the PDU session, the determination being performed based on the first message.