COMMUNICATION NODE, AND RING CONFIGURATION METHOD AND RING ESTABLISHMENT METHOD IN COMMUNICATION SYSTEM

A plurality of communication nodes are one-to-one connected to each other by Ethernet (registered trademark) which is duplicated with a normal-system ring and with a standby-system ring. The communication node includes an A port, a B port, and a communication processor that performs a process of receiving a frame output from the B port and a process of transmitting the frame from the normal-system ring from the B port when the communication is normal. When other communication node performs a loop-back process due to communication abnormality, the communication node performs only a process of forwarding a frame input from the standby-system ring in the B port without receiving the frame and performs a process of transmitting the frame from the A port to the standby-system ring.