A communication system comprising: an information provider device (Nx) on an external network; a first communication device connected to the external network; and a plurality of second communication devices (N1-Nn) connected to the first communication device, wherein each of the second communication devices (N1-Nn) is adapted to communicate with the information provider device (Nx) through the first communication device, wherein when a second communication device of the plurality of second communication devices (N1-Nn) as an information requester sends a request message for requesting network information of a radio access network to the information provider device (Nx) and receives a first response message including the network information from the information provider device (Nx) through the first communication device, the first communication device is configured to acquire the network information from the first response message and to store the network information, and when the first communication device receives, from the second communication device, a request message requesting network information, the first communication device is configured to determine whether or not the information requested with the request message is already stored in the first communication device, and if the network information requested with the request message is already stored in the first communication device, the first communication device is configured to read the stored network information and to send the read network information to the second communication device in a second response message, wherein the second communication device as the information requester is configured to designate an acquisition period of the network information, and when the first communication device receives a request message from the second communication device with the acquisition period of the network information, if the network information stored in the first communication device was acquired by the first communication device within the acquisition period, the first communication device is configured to read the information stored at the first communication device and to send the read information to the second communication device. an information provider device (Nx) on an external network; a first communication device connected to the external network; and a plurality of second communication devices (N1-Nn) connected to the first communication device, wherein each of the second communication devices (N1-Nn) is adapted to communicate with the information provider device (Nx) through the first communication device, wherein when a second communication device of the plurality of second communication devices (N1-Nn) as an information requester sends a request message for requesting network information of a radio access network to the information provider device (Nx) and receives a first response message including the network information from the information provider device (Nx) through the first communication device, the first communication device is configured to acquire the network information from the first response message and to store the network information, and when the first communication device receives, from the second communication device, a request message requesting network information, the first communication device is configured to determine whether or not the information requested with the request message is already stored in the first communication device, and if the network information requested with the request message is already stored in the first communication device, the first communication device is configured to read the stored network information and to send the read network information to the second communication device in a second response message, wherein the second communication device as the information requester is configured to designate an acquisition period of the network information, and when the first communication device receives a request message from the second communication device with the acquisition period of the network information, if the network information stored in the first communication device was acquired by the first communication device within the acquisition period, the first communication device is configured to read the information stored at the first communication device and to send the read information to the second communication device.