Upon receiving a mobile communication control signaling at the time when a mobile terminal 80 makes or receives a call, VPN gateway 100, which serves as a relay node, performs reception determination in cooperation with policy server 200 serving as a bandwidth control mechanism within LAN 20 which is a private network. When permitting the reception, the VPN gateway 100 provides a communication line to the mobile terminal 80 or a pre-shared key is dynamically generated between a radio base station and radio network controller 70, and the pre-shared key is notified to the VPN gateway 100 by the radio network controller 70.