Patent ID: 7619987

Claim:
A network system comprising at least one non-redundant node device belonging to a first ring network, connected to a second ring network with a plurality of working redundant node devices belonging to the second ring network, wherein the non-redundant node device comprises: a topology table; a transmitter transmitting topology information of the non-redundant node device; a topology table preparing portion preparing the topology table based on the topology information of the non-redundant node device itself, the topology information received from the non-redundant node device, and the topology information and redundancy information received from each redundant node device; and a packet distributor distributing received packets over the first ring network based on the topology table; and wherein each redundant node device comprises: a topology table; a transmitter transmitting topology information and redundancy information of the redundant node device itself; a topology table preparing portion preparing the topology table based on the topology information and the redundancy information of the redundant node device itself, the topology information received from a non-redundant node device, and the topology information and the redundancy information received from each redundant node device; and a packet distributor distributing received packets over the second ring network based on the topology table.