Communication System, Communication Device, and Management Method for Communication System

A communication device comprising:

• a communication portion configured to communicate with another communication device;
• a storage portion that stores system information including address information and information on availability of communication of the other communication device;
• and
• a control portion,
• wherein the control portion, by using the communication portion, is configured to:
• transmit the system information to the other communication device periodically;
• and
• determine whether an acknowledgement message in response to the transmission of the system information has been received from the other communication device or not, and, when the acknowledgement message has not been received from the other communication device, rewrite the information on availability of communication of the other communication device as incommunicable, and update the system information accordingly.

A management method for a communication system having communication devices which are connected to one another through a network, the management method comprising:

• transmitting system information including address information and information on availability of communication of the communication devices to each of the communication devices periodically from a root device which is one of the communication devices;
• sending from each of the communication devices an acknowledgement message to the root device when receiving the system information;
• and
• determining whether the acknowledgement message has been sent from each of the communication devices or not in the root device, and, when an acknowledgement message from one of the communication devices has not been received by the root device, rewriting the information on availability of communication of the communication device from which the acknowledgement message has not been received by the root device, as incommunicable, and updating the system information accordingly in the root device.