The present description discloses a method for performing network selection and traffic routing by a mobility management entity (MME). The method comprises the steps of: if a request for a public data network (PDN) connection is received from a user equipment (UE), an MME deciding whether or not the PDN connection is to be offloaded to a wireless local area network (WLAN) on the basis of an indication for WLAN offloadability obtained from a home subscriber server (HSS); the MME transmitting to the UE a message comprising information about a network-based IP flow mobility (NBIFOM) function and the decision result with respect to the PDN connection; and the MME transmitting the decision result with respect to the PDN connection to a PDN gateway (P-GW) and/or a policy and charging rules function (PCRF), wherein the decision result with respect to the PDN connection and the information about the NBIFOM function can be used for triggering any one of the UE, P-GW and PCRF such that the NBIFOM function is suspended or resumed.