Method and apparatus for routing data in wireless communication system

A method for routing, by an evolved packet data gateway (ePDG), data in a wireless communication system including un-trusted non-3rd Generation Partnership Project (3GPP) access, the method comprising:

• receiving uplink (UL) data through a wireless local area network (WLAN) access gateway;
• receiving parameters, which include 3GPP core network load information and a core network routing rule, from an entity of a 3GPP system;
• determining a path to route the UL data, through at least one of the 3GPP system and a non-3GPP system, based on the received parameters;
• and
• routing the UL data through at least one of the 3GPP system and the non-3GPP system,
• wherein the core network routing rule includes a 1-bit indicator indicating whether the UL data is to be transmitted through the 3GPP system or the non-3GPP system, and a transmission ratio indicating a ratio of traffic which is transmitted through the 3GPP system to traffic which is transmitted through the non-3GPP system.