Patent ID: 8675490

Claim:
A communication bandwidth control device which is included in a relay apparatus and which controls a communication bandwidth of a communication processed by the relay apparatus, the relay apparatus relaying data that is transmitted and received between, a destination apparatus which is a communication partner, and a communication request apparatus which is on a communication network and which requests for communication, the communication bandwidth control device comprising: a packet detecting section which detects a DNS response packet transmitted by a DNS server in order to respond to an inquiry, the inquiry being sent to the DNS server by the communication request apparatus regarding an IP address corresponding to a domain name of the destination apparatus; a storage section which stores, a first correspondence relationship between the domain name of the destination apparatus and a required bandwidth which is determined in advance and which is necessary for the relay apparatus to communicate with another relay apparatus during communication between the destination apparatus and the communication request apparatus, and a bandwidth currently available between the relay apparatus and the other relay apparatus; a condition judging section, which specifies the domain name of the destination apparatus based on a communication packet generated in association with a communication request from the communication request apparatus, and which acquires the required bandwidth from the first correspondence relationship, and which judges if a first condition that the required bandwidth is larger than the bandwidth currently available is satisfied; and a QoS configuring section which establishes, if the first condition is satisfied, a configuration to block the communication between the communication request apparatus and the destination apparatus, based on information included in the DNS response packet, wherein the condition judging section specifies the domain name of the destination apparatus based on a domain name included in the DNS response packet; and the QoS configuring section further includes a DNS modifying section which rewrites the IP address that belongs to the destination apparatus and that is included in the DNS response packet, to a specified IP address, if the condition judging section judges that the first condition is satisfied.