| 摘要 |
PROBLEM TO BE SOLVED: To improve a communication quality by effectively utilizing a line connected to a port turned into blocking state by a spanning tree protocol. SOLUTION: Each of bridges Br-1 to Br-m has a bridge port and performs the communication of layer 2 level. In a physical port, a frame is sent and received through the line. A bridge port state monitoring part 11 monitors a port state. A port correspondent relation table managing part 12 stores and manages a port correspondent relation table T containing the states of the bridge ports and the correspondent relations of the bridge ports and the physical port concerning a present device, and the correspondent relations of the bridge ports and the physical ports concerning a counter device. On the basis of the port correspondent relation table T, a switch part 13 performs switching of the bridge ports and the physical ports so that a logically cut line can be utilized for the other communication service. A port state management control part 14 transmits/receives port state information.
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