A UE transmits a registration request message including an S-NSSAI and receives a registration accept message including the S-NSSAI, a first cause value, and a first back-off timer value. The UE starts a back-off timer using the first back-off timer value corresponding to the S-NSSAI. In a case that the UE receives a configuration update command including the S-NSSAI, a second cause value, and a second back-off timer value before expiration of the back-off timer, the UE updates, in a case that the second back-off timer value indicates a value other than zero the back-off timer to be the second back-off timer value and stops, in a case that the second back-off timer value indicates zero, the back-off timer. In a case that the back-off timer expires or stops, the UE transmits the registration request message including the S-NSSAI or a PDU session establishment request message. This allows for provision of a communication unit for implementing a function related to management of a maximum number of UEs and/or a maximum number of PDU sessions connected for each network slice in a 5GS.