Information transmission device, information transmission system and information transmission method

An information transmission system comprising:

• a plurality of information transmission devices configured to form a ring network, wherein the information transmission device includes:
• a pair of ring ports of a first ring port and a second ring port, each configured to communicate with an adjacent another information transmission device to form a ring network therewith;
• an access port configured to communicate with a network outside of the ring network;
• a communication path setting unit configured to facilitate or cut off communication of the ring ports or the access port, based on a communication setting where a number of users exceeds a maximum number of identifiers within the network determined such that a plurality of communication paths having different priority levels and assigned with the same identifiers have different sections in the ring network;
• a control signal transmission unit, when a communication failure occurs between the first ring port and another information transmission device, configured to transmit, from the second ring port, a first control signal for instructing a cutoff of communication of the access port in the communication path having a low priority level, and transmit a second control signal for instructing a facilitation of communication of the ring ports;
• an access port control unit, upon receiving the first control signal, configured to cut off the communication of the access port in the communication path having the low priority level;
• and
• a ring port control unit, upon receiving the second control signal, configured to facilitate communication of the ring port having non-communication failure.

An information transmission method for an information transmission system including a plurality of information transmission devices forming a ring network and having a pair of ring connection ports connected to ring networks respectively and an external connection port connected to a network outside of the ring network, the information transmission method comprising:

• causing, in all of the information transmission devices, a facilitation or a cutoff of communication of two ring ports for communicating with an adjacent another information transmission device that forms the ring network and an access port for communicating with a network outside of the ring network, based on a communication setting where a number of users exceeds a maximum number of identifiers within the network determined such that a plurality of communication paths having different priority levels and assigned with the same identifiers pass different sections in the ring network;
• when a communication failure occurs between specific information transmission devices,
• causing transmission of, from one of the ring ports at which the communication failure did not occur to the specific information transmission devices, a first control signal for instructing a cutoff of communication of the access port in the communication path having a predetermined low priority level;
• causing all of the information transmission devices to receive the first control signal and to cut off communication of the access port in the communication path having the low priority level;
• causing the specific information transmission devices to transmit a second control signal for instructing a facilitation of communication of the ring port at which the communication failure did not occur;
• and
• causing all the information transmission devices to receive the second control signal and to facilitate communication of the ring port at which the communication failure did not occur.