Patent ID: 7499451

Claim:
A computer node that is a physical computer node in a cluster system for providing at least one virtual computer node for a client, comprising: an IP layer for storing an IP management table of a corresponding table of a virtual IP address that is an IP address of the virtual computer node and a real IP address that is an IP address of the physical computer node, and performing communication using the virtual IP address based on the IP management table; a network device connected to an other computer node and the client through a network; and an application executing unit for executing an application designated from the client, wherein the IP layer includes: an encapsulating unit for retrieving a real IP address corresponding to a virtual IP address of a destination by using the IP management table when a first packet added with a first IP header with the virtual IP address as a destination from the application executing unit is inputted, encapsulating to further add a second IP header with the retrieved real IP address as a destination to the first packet, and outputting the obtained second packet to the network device; and a decapsulating unit for generating a fourth packet by removing a third IP header from a third IP packet when the third packet added with the third IP header with the real IP address as a destination from the network device is inputted, and outputting the obtained fourth packet to the application executing unit when the virtual IP address of the fourth IP header with the virtual IP address as a destination is the virtual IP address of its own computer node.