WDM network system for performing bidirectional transmission, and node device and transmission control method used in the system

摘要

This application provides a network system that can obviate the need for arbitration control, and can realize bidirectional communications and loopback communications. In the network system, a first channel to be transmitted in the first direction, a second channel to be transmitted in the second direction, and third and fourth channels distinguished from the above-mentioned channels are used, and the packet to be looped back is transmitted using either the third or fourth channel. The transmission direction of the third or fourth channel is determined or changed in the self node device or in another node device, thus realizing loopback communications. In order to output a packet temporarily stored in a buffer using a desired channel, a device for changing the channel to which the buffer is connected is used, and the packet is read out from the buffer in correspondence with the changed channel to be connected. As the device for changing the channel to which the buffer is connected, a variable channel transmitter or a selector is used.