A method for establishing a plurality of protocol data unit (PDU) sessions between a user equipment (UE) and a data network (DN) by the UE may comprise transmitting a message to establish the plurality of PDU sessions to at least one network function (NF) of a plurality of NFs, exchanging a signal to establish the plurality of PDU sessions among the UE, a radio access network (RAN), and the plurality of NFs based on the message, and establishing the plurality of PDU sessions between the UE and the DN according to predetermined priority and based on the signal, wherein each of the plurality of PDU sessions corresponds to a network slice (NS) for a particular service, wherein the message includes information about the particular service corresponding to the plurality of PDU sessions, and wherein the priority is determined based on the information about the particular service.