Abstract: A method for preventing a control packet loop in a network realizing node redundancy or circuit redundancy based on a rapid spanning tree protocol or a multiple spanning tree protocol is disclosed. The method includes the steps of: detecting a loop of a control packet of the rapid spanning tree protocol or the multiple spanning tree protocol; and discarding the control packet by which the loop is detected so as to prevent occurrence of the loop of the control packet.

Abstract: An arbitrary node that belongs to a virtual LAN sends a request packet including a count value indicating the number of communication hops across nodes to each of its adjacent nodes that belong to the virtual LAN and are adjacent. Upon receiving the request packet, each of the adjacent nodes sends the request packet in which the count value is incremented or decremented to each of its adjacent nodes that belong to the virtual LAN and are adjacent to the node, excluding a sender of the request packet received, and sends a reply packet including the sender's address, an address of the node that is a replying node, and the count value to a given return destination. The return destination collects reply packets sent thereto and keeps track of the topology of the nodes constituting the virtual LAN from information contained in the reply packets.

Abstract: A fault detection device capable of detecting network faults by itself with high accuracy in multi-vendor environments, without the need to interoperate with an associated device according to an identical protocol. A monitoring control packet transmitter generates a fault monitoring control packet and transmits the generated packet to the associated device with which the fault detection device need not interoperate to detect faults according to the same protocol. A transmit packet counter keeps count of the transmitted fault monitoring control packet. A receive packet counter receives a control packet transmitted from the associated device, and keeps count of the received control packet. A fault detector monitors the count of transmitted packets and the count of received packets and, if at least one of the counts remains unchanged for a fixed period of time, judges that a fault has occurred and sends a fault notification to outside.

Abstract: When a control packet is transmitted/received among devices that support a spanning tree protocol (STP), a receiving side device temporarily stores a received control packet in a buffer. When the transmission of a control packet from a transmitting side device is stopped, the control packet stored in the buffer is transferred to a STP processing unit in a specific cycle. Alternatively, the transmitting side device autonomously transmits a control packet for a specific period at specific intervals from when the STP processing unit stops its operation until it restarts the operation according to an instruction to start an automatic transmission.

Abstract: An optical crossconect device comprises an optical switch, input optical level monitoring unit for monitoring optical levels of optical signals supplied to there to, signal generating unit for generating a monitoring signal to monitor the optical switch, input optical signal selecting unit for selecting the monitoring signal generated by the monitoring signal generating unit provided between the optical transmission signal input unit and the optical switch and for supplying the selected optical signal to the optical switch, and input optical signal controlling unit for controlling the input optical signal selecting unit based on an output of the input optical level monitoring unit.

Abstract: A bridge apparatus, which enables communications to continue even if a fault or a disability of operation occurs, causing the spanning tree protocol to become inoperable and, furthermore, provides a network capable of keeping track of status changes thereof, are provided by a bridge apparatus constituting a network connected with other bridge apparatus, comprising an STP protocol processing unit for carrying out a spanning tree protocol; a port for transmitting and receiving a bridge protocol data unit with the other bridge apparatus; a fault detection unit for detecting a fault of the spanning tree protocol by monitoring the STP protocol processing unit; and a for-fault time BPDU transmission unit for transmitting a for-fault time bridge protocol data unit to the other bridge apparatus by way of the port if the fault detection unit detects a fault, or a disability of operation, of the spanning tree protocol.

Abstract: A communication apparatus that detects a network failure by itself, without using any particular protocol to interact with other apparatuses in a multivendor virtual LAN (VLAN) environment. The communication apparatus has a group of physical link ports, including first and second ports, to provide physical link connections to an opposite apparatus. A virtual link from the first port to the second port is formed by tunneling through the opposite apparatus. A tagged packet transmission and receiving section transmits outgoing tagged packets from the first physical link port, while receiving incoming tagged packets arriving at the second physical link port. A failure detection section detects a failure on the VLAN by checking whether every tagged packet sent out of the first port can return to the second port via the virtual link that tunnels through the opposite apparatus.

Abstract: A fault detection device capable of detecting network faults by itself with high accuracy in multi-vendor environments, without the need to interoperate with an associated device according to an identical protocol. A monitoring control packet transmitter generates a fault monitoring control packet and transmits the generated packet to the associated device with which the fault detection device need not interoperate to detect faults according to the same protocol. A transmit packet counter keeps count of the transmitted fault monitoring control packet. A receive packet counter receives a control packet transmitted from the associated device, and keeps count of the received control packet. A fault detector monitors the count of transmitted packets and the count of received packets and, if at least one of the counts remains unchanged for a fixed period of time, judges that a fault has occurred and sends a fault notification to outside.

Abstract: A method for preventing a control packet loop in a network realizing node redundancy or circuit redundancy based on a rapid spanning tree protocol or a multiple spanning tree protocol is disclosed. The method includes the steps of: detecting a loop of a control packet of the rapid spanning tree protocol or the multiple spanning tree protocol; and discarding the control packet by which the loop is detected so as to prevent occurrence of the loop of the control packet.

Abstract: An arbitrary node that belongs to a virtual LAN sends a request packet including a count value indicating the number of communication hops across nodes to each of its adjacent nodes that belong to the virtual LAN and are adjacent. Upon receiving the request packet, each of the adjacent nodes sends the request packet in which the count value is incremented or decremented, as predetermined, to each of its adjacent nodes that belong to the virtual LAN and are adjacent to the node, excluding a sender of the request packet received, and sends a reply packet including the sender's address (sender address), an address of the node that is a replying node (replying node address), and the count value to a given return destination. The return destination collects reply packets sent thereto and keeps track of the topology of the nodes constituting the virtual LAN from information contained in the reply packets.

Abstract: An inter-ring connection device connecting at least two rings, each consisting of network devices connected in a ring shape. Each of the network devices transmits/receives topology constituting data including its address and information indicating its position. Each of the rings functions as a network device and generates a topology map. The inter-ring connection device includes setting information storage means and transfer means. The setting information storage means stores one of the setting information for creating a topology map of a physical ring and setting information for creating a topology map of a virtual ring striding over two physical rings. When transferring topology constituting data to another adjacent network device, only if the setting information is the information for creating a topology map of a virtual ring, the transfer means transfers the topology constituting data to the other adjacent network device striding over two physical rings.

Abstract: When a control packet is transmitted/received among devices that support a spanning tree protocol (STP), a receiving side device temporarily stores a received control packet in a buffer. When the transmission of a control packet from a transmitting side device is stopped, the control packet stored in the buffer is transferred to a STP processing unit in a specific cycle. Alternatively, the transmitting side device autonomously transmits a control packet for a specific period at specific intervals from when the STP processing unit stops its operation until it restarts the operation according to an instruction to start an automatic transmission.

Abstract: An optical crossconect device comprises an optical switch, input optical level monitoring unit for monitoring optical levels of optical signals supplied to there to, signal generating unit for generating a monitoring signal to monitor the optical switch, input optical signal selecting unit for selecting the monitoring signal generated by the monitoring signal generating unit provided between the optical transmission signal input unit and the optical switch and for supplying the selected optical signal to the optical switch, and input optical signal controlling unit for controlling the input optical signal selecting unit based on an output of the input optical level monitoring unit.