Two priority fair distribution round robbin protocol for network having cascaded hubs

PROBLEM TO BE SOLVED: To provide a two priority protocol for selecting an end node to transmit a network packet on a network. SOLUTION: For example, the network packet is a high priority packet or an ordinary priority packet. When the end node has the high priority packet to be transmitted, high priority is requested to a hub. When the end node has the ordinary priority packet, on the other hand, ordinary priority is requested to that hub. When the high priority or ordinary priority is requested, the end node transmits the packet after waiting a positive response from the hub. When one end node has the high priority packet at least, the respective end nodes having that packet are successively approved. After approval, the respective end nodes transmit these packets onto the network. After all the high priority packets are transmitted, ordinary priority packets are transmitted. When one end node has the ordinary priority packet at least and there is no end node having the high priority packet, the respective end nodes having the ordinary priority packets are successively approved.