In a communication system of a subscriber extension line system, there is provided a communication controller whereby the load of an unnecessary process to be applied on a communication controller relating to a destination of a mobile telephone is eliminated and the processing efficiency for communication control is enhanced. In a D-RNC which controls the communication of the mobile telephone and which is commonly connected with an S-RNC, the mobile telephone moves while maintaining the communication with the S-RNC. When the mobile telephone enters a cell relating to the D-RNC, the control data is transmitted or received between the S-RNC and the node for managing the mobile telephone. There are also provided: an IP address/UDP port number for RNSAP, reading/setting section 316 for acquiring an IP address identifying the S-RNC and an IP address identifying the node; an IP address/UDP port number for NBAP, reading/setting section 315; and an IP address/UDP port number exchange section 314 for notifying the other side of the S-RNC and the node of the acquired IP addresses, respectively. This allows a direct communication between the S-RNC and the node.