Provided in one disclosure of the present specification is a method selecting a network and routing traffic by a user equipment (UE). The method may comprise a step of receiving, from a base station, radio access network (RAN) support information, wherein the RAN support information may include RAN support parameters and a timer value. The method comprises the steps of: receiving, from an upper layer, an evaluation request; evaluating the RAN support parameters according to the request from the upper layer; delivering, to the upper layer, an indication which indicates a detour to wireless local area network (WLAN) access and a detour to 3GPP access according to the result of the evaluation, and/or an indication which indicates maintaining current access; and performing feedback to the step of evaluating when the timer expires.