Abstract: A client apparatus includes a wireless network access unit configured to access wireless networks, a packet analysis unit configured to analyze uplink and downlink data packets, a security tunnel processor configured to establish a mobile security tunnel and to maintain the established mobile security tunnel when handover is performed in heterogeneous networks, a wireless network controller configured to control a wireless network accessing process and a connection releasing process of the wireless network access unit, a mobile security tunnel controller configured to perform a MOBIKE protocol and to control a process of establishing and maintaining a mobile security tunnel of the security tunnel processor, and a wireless network connection manager configured to request the mobile security tunnel controller to perform a MOBIKE protocol by managing MOBIKE information and to control handover by setting up and managing a wireless network access policy.