Patent ID: 7672320

Claim:
An IP (Internet protocol) communications system comprising: one of a plurality of gateway devices having a subscriber terminal interconnected thereto; a gateway controller provided on a subscriber side in accordance with a protocol complying with a master-slave architecture for controlling said gateway device; a subscriber information database for supplying subscriber information to said gateway controller; and an IP address allocator for dynamically allocating IP addresses; said gateway device requesting said IP address allocator to allocate an IP address to acquire the IP address, said IP address then being notified to said gateway controller, said IP address allocator including a relationship between identification information of all of said plurality of gateway devices allowed for donation of the IP addresses and identification information of said gateway controller supervising said plurality of gateway devices, and a list of IP addresses; the list of the IP addresses being constructed so that at least the identification information of said gateway device, which is a destination of allocation, is associated with a term of validity thereof, from one IP address to another, the identification information of said gateway device and the term of validity being held for IP addresses already allocated, neither the identification information nor the term of validity being held for IP addresses not allocated, the list being managed whether or not the IP addresses have been allocated; and said IP address allocator receiving a request for allocation of the IP address from said gateway device to confirm that said IP address allocator holds the identification information of said gateway device associated with the request, and thereafter allocating, if the identification information of said gateway device is held in the list of the IP addresses, a same IP address to update the term of validity, said IP address allocator selecting, if the identification information of said gateway device is not held in the list of the IP addresses, one of unallocated IP addresses to return the selected IP address and the identification information of said gateway controller, the identification information of said gateway device as the destination of allocation being held in a storage location of the IP address in the list of the IP addresses together with the term of validity associated therewith.