Mitsubishi Electric Corporation

Sachiko Taniguchi

Ryusuke Kawate

Ayako Inoue

Yuji Goto

Toshiyuki Nakayasu

Yusuke Sakagami

Yoshifumi Hotta

Ryuma Matsushita

Shingo Honda

Ryohei Kuba

Motonobu Jutori

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 () is provided with a destination determination unit () to transfer, when a time clocked by a timer unit () to start clocking is within a set time, a frame to ports (and) connected to trunk circuits (and), and when the time clocked by the timer unit () exceeds the set time, to transfer the frame to the ports (and) connected to the trunk circuits (and) and a port () connected to a branch circuit (), in a case wherein it is impossible for a search unit () to obtain from a first storage unit () a port number corresponding to a destination address included in the frame received, and the first storage unit () is cleared.

Relay device, relay system, relay method and computer-readable recording medium that reduce a traffic load on a communication device

A time-point synchronization apparatus () includes a time-point management unit (), a time-gap counter (), and a time-gap calculation unit (). The time-point management unit () manages an apparatus time point equivalent to a current time point. The time-gap counter () records a time gap which is a different between a time point indicated in reception information and the apparatus time point. When a frequency in the time-gap counter (), corresponding to the time gap corresponding to a latest reception time point corresponding to latest reception information is treated as the highest among all of frequencies indicated in the time-gap counter (), the time-gap calculation unit () synchronizes the apparatus time point to the latest reception time point.

Time-point synchronization apparatus, time-point synchronization method, and non-transitory computer readable medium

A relay device includes a plurality of physical ports (-to-N) that receive frames, and a layer-protocol processing unit () that transfers the frame received by one of the physical ports (-to-N) from at least one of the physical ports (-to-N). The layer-protocol processing unit () 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 (-to-N) as a port that relays only the clock-time synchronization frame used for synchronizing clock time.

Relay device and communication system

An information obtaining unit () of a monitoring apparatus () obtains from each node, topology map information created in each node by an exchange of information and sharing of information between nodes that belong to a ring network. The topology map information is information that indicates a connection relation between the nodes in the ring network. A topology comparison unit () of the monitoring apparatus () compares the topology map information obtained from each node by the information obtaining unit () with topology definition information retained in a memory () beforehand, and determines whether or not a configuration of the ring network is according to design. The topology definition information is information that defines the connection relation between the nodes in the ring network.

Monitoring apparatus, network system, topology management method, and computer readable medium

A communication apparatus is mounted on a train and forms a train communication system together with a system control apparatus that generates control frames including general and low-latency frames. The communication apparatus includes: a general transfer processing unit that stores the general frame; a low latency transfer processing unit that stores the low-latency frame, the low latency frame requiring transferring with lower latency than the general frame; a frame identification unit that identifies priority of the control frame and outputs the control frame to the general transfer processing unit or the low latency transfer processing unit based on a priority setting table indicating the priority of the control frame and set in the identification unit; an output control unit that preferentially transfers the low-latency frame over the general frame; and a control unit that modifies the priority setting table.

Communication apparatus, system control apparatus, train communication system, and communication method for controlling transmission of low latency frames and general frames

A transfer device includes an output-port decision unit to decide, on the basis of storage information stored in a frame input, an output port from which the frame is output from among a plurality of ports, an allocation unit to associate an input port to which the frame is input with an output port from which a frame which is transferred by a cut-through method is output on a one-to-one basis, and allocate a first frame to a first pathway transferring by the cut-through method and allocate a second frame to a second pathway transferring by a store-and-forward method on the basis of type information of an input port to which a frame has been input, class information of the frame, and the output port decided by the output-port decision unit, and an IET-output control unit to output the first frame from the output port, decide whether to divide the second frame on the basis of the class information of the second frame, and output the second frame from the output port on the basis of decision. Therefore, the transfer device can realize an IET low-latency transfer function by control simpler than that in the conventional transfer devices.

Transfer device, transfer method, and transfer system

Provided is a transfer device () that includes a plurality of ports to and from each of which a layer-2 frame is input and output; a frame identification unit () that identifies whether or not the frame has been encrypted; an address filter unit () that decides one of the plurality of ports from which the frame is to be output; an encryption necessity determination unit () 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 () that encrypts the frame for which it has been determined that encryption is necessary and decrypts the frame for which it has been determined that decryption is necessary; and a switching processing unit () that outputs the frame to one of the ports. Thus, the transfer device can realize both encrypted communication and plaintext communication.

Transfer device and communication network

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.

Transfer device and frame transfer method

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.

Relay device and communication network

A transfer apparatus has an input port and an output port, an input line speed of the input port and an output line speed of the output port being capable of being set to differ from each other. The transfer apparatus comprises, for each output port: a low-latency frame transmission buffer to store a low-latency frame received at the input port; a normal-latency frame transmission buffer to store a normal-latency frame that is a frame received at the input port, the normal-latency frame being permitted to be transferred with higher latency than the low-latency frame; a time calculation unit to calculate output start time of the low-latency frame by using information on a frame length of the low-latency frame, the input line speed, and the output line speed when the low-latency frame is received; and an output contention control unit to control transfer of the low-latency frame and the normal-latency frame by using the output start time.

Transfer apparatus and frame transfer method

The relay device includes: a frame determination unit that determines a received frame between a high-priority frame and a low-priority frame for each output port on a basis of an identifier; a fixed-delay queue that delays the high-priority frame for a time equal to or longer than the sum of a specified transmission gap and a frame length long enough for a downstream device to be capable of correctly receiving and transferring or discarding a frame, and that transmits the high-priority frame; a low-priority frame storing unit that stores therein the low-priority frame; a transmission-frame selection unit that executes control to discontinue transmission of the low-priority frame when transmitting the high-priority frame, and to retransmit the low-priority frame; and an output control unit that selects a frame to be transmitted to the downstream device on a basis of the control by the transmission-frame selection unit.

Relay device and data transfer method

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.

Transfer device

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.

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Tokyo, Japan

Sachiko Taniguchi