Abstract: User information stored in a second server as a proxy authentification device is deleted from a first server performing authentification of the network connection. Accordingly, it is possible to easily and surely delete the user information stored in one of the plurality of second servers from the first server. That is, it is possible to delete user information stored in a server such as a proxy server acting for authentification in a short period of time.

Abstract: An IP communication network system has a plurality of autonomous systems, configuring IP networks of domains independent of each other, for performing interior- and exterior-forwarding of IP packets. The plurality of autonomous systems include a plurality of border relay devices positioned at borders between the IP networks. Each of the plurality of border relay devices includes 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 for detecting the re-intrusion of the unauthorized packet, and a distribution unit for distributing the filtering information to all other border relay devices within the same autonomous system.

Abstract: An IP communication network system has a plurality of autonomous systems, configuring IP networks of domains independent of each other, for performing interior- and exterior-forwarding of IP packets. The plurality of autonomous systems include a plurality of border relay devices positioned at borders between the IP networks. Each of the plurality of border relay devices includes 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 for detecting the re-intrusion of the unauthorized packet, and a distribution unit for distributing the filtering information to all other border relay devices within the same autonomous system.