<p>A chip in each cross bar switch generates and issues a packet for log collection for collecting logs of packets when it is inputted with a packet. It also collects logs about the transfer of inputted packets. It embeds the collected logs in the issued packet for log collection or a packet for log collection transferred from a cross bar switch in the previous stage. When the forwarding destination of the packet is other than a cross bar switch, the logs embedded in the packet for log collection are stored in a storage portion and the packet from which the logs have been eliminated is transferred to the forwarding destination. When the forwarding destination is a cross bar switch, on the other hand, the packet for log collection is transferred to a cross bar switch in the subsequent stage.</p>
