A disclosure of the present specification provides a method for processing establishment of a protocol data unit (PDU) session by an access and mobility management function (AMF) node. The method may include a step of receiving a PDU session establishment request message from a user equipment (UE) via either a first access or a second access. The PDU session establishment request message may include information indicative of a multi access (MA) PDU session. The method may include a step of selecting a session management function (SMF) node supporting the MA PDU session on the basis of the information indicative of the MA PDU session. The method may include a step of sending the PDU session establishment request message to the SMF node supporting the MA PDU session.