NETWORK RELAY DEVICE, DDOS PROTECTION METHOD EMPLOYING THE DEVICE, AND LOAD DISTRIBUTION METHOD

摘要

PROBLEM TO BE SOLVED: To protect a DDoS attack or to effectively distribute a load of a network server by promptly fetching information relating to network security.SOLUTION: A network relay device includes: tables in which a detection condition relating to a packet and an identification code are stored and of which the active side and the reserve side can be switched in a complementary manner; table switching means for switching the active side and the reserve side of the tables; packet condition registration means by which a detection condition from the outside is inputted and registered in the reserve-side table; packet reception means for receiving a packet addressed from one device to another device; collation means for determining whether or not the received packet is matched with the packet condition in the active-side table; packet processing means for executing processing contents corresponding to the packet condition in the case where the packet is matched with the condition as a result of the determination; and monitoring means for detecting an abnormality from an input cycle or the like in the detection condition. The table switching means switches the active side and the reserve side of the tables in response to detecting the abnormality by the monitoring means.