Patent ID: 7738362
Filing Date: 2010-06-15
Classification: H04J,H04L

Abstract:
1. A network system comprising: a service providing apparatus; first and second backup apparatuses, each of which is configured to back up at least a part of a function of said service providing apparatus, and is connected with said service providing apparatus through a WAN; and a terminal connected with said service providing apparatus and said first and second backup apparatuses, and configured to receive a service from said service providing apparatus in a normal operation, wherein said service providing apparatus has IP addresses of itself, said first and second backup apparatuses and said terminal, and notifies the IP addresses of said service providing apparatus and said first backup apparatus to said terminal in response to registration of the IP address of said terminal, and said terminal holds the IP addresses of said service providing apparatus and said first backup apparatus, and registers the IP address of said terminal on said first backup apparatus based on the IP address of said first backup apparatus to receive a service from said first backup apparatus, when knowing a communication failure with said service providing apparatus, said service providing apparatus notifies the IP address of said second backup apparatus as at least one substitution backup apparatus to said terminal when knowing a communication failure with said first backup apparatus, and said terminal holds the IP address of said second backup apparatus in place of the IP address of said first backup apparatus, and registers the IP address of said terminal on said second backup apparatus based on the IP address of said second backup apparatus to receive a service from said second backup apparatus, when knowing the communication failure with said service providing apparatus, said terminal communicates with said first backup apparatus periodically to detect the communication failure with said first backup apparatus, and notifies the detection of the communication failure with said first backup apparatus to said service providing apparatus, said service providing apparatus has an IP address list of the IP addresses of a plurality of backup apparatuses including said first and second backup apparatuses, and transmits said IP address list to said terminal in response to the notice of the detection of the communication failure with said first backup apparatus from said terminal, said terminal checks a response time of each of said plurality of backup apparatuses other than said first backup apparatus based on said IP address list, and notifies the check result to said service providing apparatus, and said service providing apparatus selects said second backup apparatus as said at least one substitution backup apparatus from among said plurality of backup apparatuses and notifies the IP address of said second backup apparatus to said terminal.