In an NoC bus system, data is transmitted between first and second nodes through a router. The data includes performance-ensuring data which guarantees throughput and/or a permitted time delay. The first node generates packets, each including the data to be transmitted and classification information that indicates the class of that data to be determined according to its required performance, and controls transmission of the packets. The router includes a buffer section configured to store the received packets separately after having classified the packets according to their required performance by reference to the classification information, and a relay controller configured to control transmission of the packets stored in the buffer section at a transmission rate which is equal to or higher than the sum of transmission rates to be guaranteed for every first node associated with the classification information by reference to each piece of the classification information.