| 主权项 |
1. A communication network comprising:
a plurality of relay devices each including a plurality of ports for frame transmission and reception, wherein: the ports of each relay device include two specific ports; the relay devices are connected in a ring shape by connecting the two specific ports of the relay devices; each relay device includes a storage for storing
identification information of other relay devices, which constitutes the relay devices connected in the ring shape, andconnection information indicating an order in which the other relay devices are connected when viewed from the relay device; a master relay device, which is one of the relay devices, includes an abnormality detection frame transmission section and a master side specification section; the abnormality detection frame transmission section transmits an abnormality detection frame at fixed time intervals from one of the two specific ports of the master relay device, wherein the one of the two specific ports from which the abnormality detection frame is transmitted is a first specific port and the other of the two specific ports is a second specific port; and when neither the frame abnormality detection nor an abnormality notification frame transmitted from another relay device is received from the second specific port of the master relay device within a predetermined time period from transmission of the abnormality detection frame from the abnormality detection frame transmission section, the master side specification section
specifies, from the connection information, the identification information of a first-connected relay device which is the relay device that is first connected when viewed from the second specific port of the master relay device,specifies an occurrence of an abnormality in a communication path between the first-connected relay device and the second specific port of the master relay device, andtransmits, from the first specific port, an abnormality notification frame that contains the identification information of the master relay device; the relay devices other than the master relay device are slave relay devices; each slave relay device includes an abnormality detection frame forwarding section and a slave side specification section; the abnormality detection frame forwarding section of the salve relay device, upon receipt of the abnormality detection frame from any one of the two specific ports, transmits the received abnormality detection frame from the other of the two specific ports; of the two specific ports of each slave relay device, one from which the abnormality detection frame is received is an upstream side specific port and the other is a downstream side specific port; when neither the abnormality detection frame nor the abnormality notification frame transmitted from another relay device is received from the upstream side specific port of the slave relay device within a predetermined time period from receipt of the abnormality detection frame at the upstream side specific port of the slave relay device, the slave side specification section of the slave relay device
specifies the identification information of a first-connected relay device which is the relay device that is first connected when viewed from the upstream side specific port,specifies an occurrence of an abnormality in a communication path between the first-connected relay device and the upstream side specific port, andtransmits, from the downstream side specific port, an abnormality notification frame that contains the identification information of the slave relay device; each of the master relay device and the slave relay devices includes a notification reception process section; when one of the two specific ports of the relay device receives the abnormality notification frame transmitted from another relay device, the notification reception process section of the relay device
transmits the received abnormality notification from the other of the two specific ports,specifies, from the connection information, the identification information of a particular-away relay device which is the relay device that is, when viewed from the one of the two specific ports which received the abnormality notification frame, connected next to and on a far side of the relay device identified by the identification information contained in the received abnormality notification frame, andspecifies an occurrence of an abnormality in a communication path between the particular-away relay device and the relay device identified by the identification information contained in the received abnormality notification frame. |
