Abstract: The conventional relay device has a problem that a traffic load on a communication device is large when an output port of a frame including a destination address, which an address table has not learned yet, is a port connected to a branch circuit, since flooding is performed on all ports except for a port that has received the frame. A relay device (21) is provided with a destination determination unit (41) to transfer, when a time clocked by a timer unit (40) to start clocking is within a set time, a frame to ports (511 and 512) connected to trunk circuits (61 and 64), and when the time clocked by the timer unit (40) exceeds the set time, to transfer the frame to the ports (511 and 512) connected to the trunk circuits (61 and 64) and a port (513) connected to a branch circuit (65), in a case wherein it is impossible for a search unit (43) to obtain from a first storage unit (33) a port number corresponding to a destination address included in the frame received, and the first storage unit (33) is cleared.

Abstract: A relay device includes a plurality of physical ports (111-1 to 111-N) that receive frames, and a layer-2 protocol processing unit (113) that transfers the frame received by one of the physical ports (111-1 to 111-N) from at least one of the physical ports (111-1 to 111-N). The layer-2 protocol processing unit (113) has a filtering function for blocking frames other than a clock-time synchronization frame during transfer involving a port selected from the plurality of physical ports (111-1 to 111-N) as a port that relays only the clock-time synchronization frame used for synchronizing clock time.

Abstract: Provided is a transfer device (200) that includes a plurality of ports to and from each of which a layer-2 frame is input and output; a frame identification unit (221) that identifies whether or not the frame has been encrypted; an address filter unit (222) that decides one of the plurality of ports from which the frame is to be output; an encryption necessity determination unit (223) that has an encryption necessity determination table depending on destination information and priority information which are included in each frame, and a decryption necessity determination table depending on the destination information included in each frame, and when the frame has not been encrypted, determines whether or not encryption is necessary for the frame based on the encryption necessity determination table, and when the frame has been encrypted, determines whether or not decryption is necessary for the frame based on the decryption necessity determination table; an encryption decryption processing unit (225) that enc

Abstract: To include an FCS code calculation unit to calculate a first code that is an FCS code of a received frame, an FCS check unit to compare the first code with a second code that is an FCS code stored in the received frame, and to output a first comparison result indicating a match or no match between two codes, an inverse FCS check unit to compare the first code with a third code obtained by inverting each bit of the second code, and to output a second comparison result indicating a match or no match between two codes, an error determination unit to determine an error state of the received frame, and an FCS update unit to update, if the second comparison result indicates no match, the second code with a fourth code obtained by inverting each bit of the first code.

Abstract: A network device (100) is included in a ring-type network system (500) which selects a time master. A link processing unit (20) generates a link for communicating a frame. The link processing unit (20) has a frame discarding function of discarding the frame in order to avoid a broadcast storm. A path control unit (108) generates a time distribution path starting at and terminating at a time master, clockwise and counterclockwise of the time master. The path control unit (108) communicates a time synchronization message out of the frame, the synchronization message being used for time synchronization of a plurality of network devices (100). A filtering unit (103), upon acquisition of the time synchronization message, makes the time synchronization message to pass through regardless of the frame discarding function.

Abstract: Provided are a redundant route calculator that calculates, on the basis of first topology information on a network made up of a plurality of transfer devices, a plurality of shortest routes from a first transfer device to a second transfer device among the plurality of transfer devices, and generates redundant route information; a forwarding database that stores the redundant route information; and a single point-of-failure detector that detects a single point of failure on the basis of the redundant route information and generates second topology information obtained by removing the single point of failure from the first topology information. On the basis of the second topology information, the redundant route calculator calculates an additional route candidate from the first transfer device to the second transfer device. The single point-of-failure detector decides the additional route to register in the forwarding database.

Abstract: Provided is a transfer device (200) that includes a plurality of ports to and from each of which a layer-2 frame is input and output; a frame identification unit (221) that identifies whether or not the frame has been encrypted; an address filter unit (222) that decides one of the plurality of ports from which the frame is to be output; an encryption necessity determination unit (223) that has an encryption necessity determination table depending on destination information and priority information which are included in each frame, and a decryption necessity determination table depending on the destination information included in each frame, and when the frame has not been encrypted, determines whether or not encryption is necessary for the frame based on the encryption necessity determination table, and when the frame has been encrypted, determines whether or not decryption is necessary for the frame based on the decryption necessity determination table; an encryption decryption processing unit (225) that enc

Abstract: A layer-2 switch, forming a communication network along with a communication terminal, includes a plurality of communication ports, frame identification units to identify a specific frame that is regularly transmitted from the communication terminal in the communication network, a setting unit to set a monitoring cycle and a reception threshold for detecting a loop path in the communication network, a monitoring unit to identify, for each of the communication ports, a plurality of communication terminals that are a source of the specific frame, and to count the number of the specific frames received from each of the communication terminals within the monitoring cycle, and a determination unit to determine whether a loop path is detected for each of the communication ports by comparing a counter value, which indicates the number of the specific frames, with the reception threshold, and to execute control to stop transmission and reception of the frame at the communication port at which a loop path is detected.

Abstract: To include an FCS code calculation unit to calculate a first code that is an FCS code of a received frame, an FCS check unit to compare the first code with a second code that is an FCS code stored in the received frame, and to output a first comparison result indicating a match or no match between two codes, an inverse FCS check unit to compare the first code with a third code obtained by inverting each bit of the second code, and to output a second comparison result indicating a match or no match between two codes, an error determination unit to determine an error state of the received frame, and an FCS update unit to update, if the second comparison result indicates no match, the second code with a fourth code obtained by inverting each bit of the first code.

Abstract: Provided are a redundant route calculator that calculates, on the basis of first topology information on a network made up of a plurality of transfer devices, a plurality of shortest routes from a first transfer device to a second transfer device among the plurality of transfer devices, and generates redundant route information; a forwarding database that stores the redundant route information; and a single point-of-failure detector that detects a single point of failure on the basis of the redundant route information and generates second topology information obtained by removing the single point of failure from the first topology information. On the basis of the second topology information, the redundant route calculator calculates an additional route candidate from the first transfer device to the second transfer device. The single point-of-failure detector decides the additional route to register in the forwarding database.

Abstract: There are provided: a transfer management table storage unit to store a transfer management table which indicates transfer destination ports for frames received from another transfer device, the another transfer device being configured to transmit a frame low in importance of received frames without copying this frame and to transmit an important frame of received frames to paths made redundant by copying the important frame, the important frame being a frame higher in importance than the frame low in importance; an adjacent information table storage unit to store an adjacent information table which indicates information about instruments connected to the ports; and a transfer destination management unit to control whether to transfer an important frame received from another transfer device by use of the transfer management table and the adjacent information table.

Abstract: A layer-2 switch, forming a communication network along with a communication terminal, includes a plurality of communication ports, frame identification units to identify a specific frame that is regularly transmitted from the communication terminal in the communication network, a setting unit to set a monitoring cycle and a reception threshold for detecting a loop path in the communication network, a monitoring unit to identify, for each of the communication ports, a plurality of communication terminals that are a source of the specific frame, and to count the number of the specific frames received from each of the communication terminals within the monitoring cycle, and a determination unit to determine whether a loop path is detected for each of the communication ports by comparing a counter value, which indicates the number of the specific frames, with the reception threshold, and to execute control to stop transmission and reception of the frame at the communication port at which a loop path is detected.

Abstract: There are provided: a transfer management table storage unit to store a transfer management table which indicates transfer destination ports for frames received from another transfer device, the another transfer device being configured to transmit a frame low in importance of received frames without copying this frame and to transmit an important frame of received frames to paths made redundant by copying the important frame, the important frame being a frame higher in importance than the frame low in importance; an adjacent information table storage unit to store an adjacent information table which indicates information about instruments connected to the ports; and a transfer destination management unit to control whether to transfer an important frame received from another transfer device by use of the transfer management table and the adjacent information table.

Abstract: A communication system includes two or more ring networks in which nodes are connected in a ring shape, carries out ERP for each of the ring networks, sets one of the ring networks as a major ring that detects a failure in a shared link, and sets the other ring networks as sub rings. A shared node, which terminates the shared link, includes: a failure monitoring unit that respectively detects, concerning two or more of the ring networks that share the shared link, failures in the ring networks; a switching processing unit that determines, on the basis of a detection result of the failures, the ring network set as the major ring; and ERP processing units that store, when the switching is performed by the switching processing unit, identification information after the switching in an R-APS frame and transfer or transmit the frame.

Abstract: A communication system includes two or more ring networks in which nodes are connected in a ring shape, carries out ERP for each of the ring networks, sets one of the ring networks as a major ring that detects a failure in a shared link, and sets the other ring networks as sub rings. A shared node, which terminates the shared link, includes: a failure monitoring unit that respectively detects, concerning two or more of the ring networks that share the shared link, failures in the ring networks; a switching processing unit that determines, on the basis of a detection result of the failures, the ring network set as the major ring; and ERP processing units that store, when the switching is performed by the switching processing unit, identification information after the switching in an R-APS frame and transfer or transmit the frame.

Abstract: An OLT 1 sequentially allocates transmission permission of a packet on an upstream transmission line to a plurality of ONUs 2 registered, and performs packet communication in a simplified method with control by using a first timer for detecting a packet signal and a second timer for controlling transmission permission time, in order to transmit an IP packet of variable length without mounting a function of complex processing for analyzing an upstream packet in the OLT 1.

Abstract: An OLT 1 sequentially allocates transmission permission of a packet on an upstream transmission line to a plurality of ONUs 2 registered, and performs packet communication in a simplified method with control by using a first timer for detecting a packet signal and a second timer for controlling transmission permission time, in order to transmit an IP packet of variable length without mounting a function of complex processing for analyzing an upstream packet in the OLT 1.

Abstract: An optical distribution network system includes an optical line termination and a plurality of optical network units. The optical line termination monitors a system switching request transmitted from each of the optical network units, and controls the switching between the working side and the standby side system of the optical network unit. It can solve a problem of a conventional system in that if the working side an optical network unit fails, and when its standby side is normal, even if the standby side of the other optical network units has a failure, they are switched from the working side to the standby side, thereby worsening the total system operation.