Abstract: In the system for communicating a management message between nodes in a wavelength division multiplexing network 1, each of the nodes has a switching unit 101 for switching a transmission path of an optical channel signal carried by the network. The optical channel signal has a frame in compliance with the SDH/SONET standard that stipulates the Data Communication Channel Bites D4-D12 in the Line Overhead Bite to be allocated for a management message. Each of the nodes includes a termination and generation means for terminating the bites D4-D12 and extracts a management message from the bites when each of the nodes receives the optical channel signal. The node judges an optical channel to carry said management message and incorporates new bites of the same bite structure as bites D4-D12 into the optical channel signal in place for the terminated bites D4-D12. The new bites are entered with a management message to be carried by the same channel as that of the optical channel signal of interest.

Abstract: In a ring network system formed by a plurality of nodes connected to one another through a ring-shaped path, each of the nodes collects all of node information signals representative of states of the nodes and memorizes the node information signals in a node information signal memory included in each node. The node information signal is periodically transmitted to each node from an adjacent one or ones of the nodes through the ring-shaped path and is renewed from time to time. Such collection of all of the node information signal in each node makes it easy to check an alarm by a superintendent.

Abstract: In a ring network where network nodes are interconnected by an optical fiber ring, one of the nodes acts as a master node and each of the other nodes acts as a slave node. The master node successively designates a different slave node in a descending order of priorities, transmits a command message to the designated slave node, and updates its memory with a response message from the designated node. If the command message is received, each designated slave node updates its memory with data contained in the command message and returns a response message to the master node. If the command message is not received, each slave node, acting as a temporary master node, designates a different one of the other slave nodes in descending order, transmits a command message to each designated node, and updates its memory with a response message therefrom.