Patent ID: 8830994

Claim:
A network system, comprising: a plurality of lower switching hubs; and one or more upper switching hubs connected to each of the lower switching hubs, to relay a normal frame to be transmitted and received between the lower switching hubs, wherein each of the lower switching hubs includes a lower switch configuring portion for configuring a first link aggregation group for all ports connected to the upper switching hub, and transmitting a first control frame containing its own identifier from all the ports connected to the one or more upper switching hubs, wherein each of the upper switching hubs includes an upper switch configuring portion for configuring a second link aggregation group for ports connected to a same lower switching hub, based on the first control frames received from the lower switching hubs, and transmitting a second control frame containing its own identifier from the ports configured as the second link aggregation group, wherein the upper switch configuring portion is configured to disable transmission and reception of the normal frame and transmission of the second control frame at a port which is not configured as the second link aggregation group, wherein the upper switch configuring portion is configured to, when receiving the first control frame at the port which is not configured as the second link aggregation group, configure the second link aggregation group for the port having received the first control frame, thereafter enable the normal frame transmission and reception, and begin the second control frame transmission, and wherein, when a transmission line is connected between the upper switching hubs and the lower switching hubs, before receiving the first control frame, the upper switching hubs operate to disable the transmission and reception of the normal frame and the transmission of the second control frame, while the lower switching hubs operate to transmit the first control frame such that respective operations of the upper switching hubs and the lower switching hubs are different.