Patent ID: 6895432

Claim:
An IP communication network system: comprising a plurality of autonomous systems, configuring IP networks of domains independent of each other, for performing interior- and exterior-forwarding of IP packets, said plurality of autonomous systems including a plurality of border relay devices positioned at borders between the IP networks, each of said plurality of border relay devices including: a discarding unit for discarding, if the IP packet forwarded is an unauthorized intrusion packet, this unauthorized packet when detecting a re-intrusion on the basis of filtering information, having at least one of the destination IP address, protocol type and port number of the unauthorized packet, for detecting the re-intrusion of the unauthorized packet; a registration processing unit having a monitoring time for detecting the re-intrusion of the unauthorized packet with respect to each of the unauthorized packets and deleting, upon the monitoring time corresponding to the unauthorized packet expiring, the information of the unauthorized packet from the filtering information; and a distribution unit for distributing the filtering information to all other border relay devices within said same autonomous system.