Hitachi, Ltd.

Hitachi Software Engineering Company, Ltd.

Atsushi Kimoto

Michio Suzuki

Masashi Ikeda

Tatsuya Watanuki

Hironari Sakai

Osamu Takada

Toshihiko Murakami

Masatoshi Takihiro

Hidehiro Fukushima

Makoto Kitani

Atsuo Hatono

Keiichiro Yamate

Shoichiro Yamaguchi

The network relay device of the invention makes a pair with at least a specific network device to relay data in a network. The network relay device includes: a control module that sends and receives a control frame signal to and from the specific network device, selects either of a master mode and a backup mode based on at least the control frame signal sent from the specific network device, and changes a working state according to a result of the selection; and a communication module that is under control of the control module to open a port and enable data transmission via a line linked to the port in the case of setting a master state to the working state, and to block off the port and disconnect the line linked to the port in the case of setting a backup state or another non-master state to the working state. The control module changes the working state from the backup state to a first intermediate state in response to selection of the master mode, determines whether the specific network device is in the backup state, based on the control frame signal sent from the specific network device, and changes the working state from the first intermediate state to the master state after confirmation that the specific network is in the backup state.

Network relay system and control method thereof

An ATM switch for providing an electrical interconnection between a connection-oriented ATM LAN of an ATM system and a connectionless legacy LAN is provided. The ATM switch includes a switch fabric electrically connected to the ATM LAN, a segmentation and reassembly block electrically connected to the switch fabric, for providing an interchange between one of cells transmitted over the ATM LAN and a packet transmitted over the legacy LAN, a management and control block electrically connected to the switch fabric through the segmentation and control block so as to manage and control operations for electrical connections between networks, a first bridging/routing processor having a legacy LAN interface for providing electrical connections between the legacy LAN and the first bridging/routing processor, a second bridging/routing processor electrically connected to the switch fabric through at least one ATM interface, and a bus for providing electrical connections between the management and control block, the first bridging/routing processor and the second bridging/routing processor. A LAN emulation configuration server function for managing configurations of a plurality of virtual LAN segments on the ATM LAN, which are required upon LAN emulation, a LAN emulation server function for obtaining an address resolution to an ATM address from a media access address, and a broadcast and unknown server function for making a broadcast to a terminal in the LAN are provided so as to be distributed to the management and control block or the second bridging/routing processor.

ATM switch and intermediate system

An ATM network includes a plurality of ATM-LANs which are connected through an ATM-WAN, when a source terminal and a destination terminal belong tb separate ATM-LANs connected through the ATM-WAN, the congestion control is performed as follows. When congestion occurs in an ATM-LAN in which the source terminal exists, the congestion control is performed by the BECN mechanism and when congestion occurs in an ATM-LAN other than the ATM-LAN in which the source terminal exists, the congestion control is performed by the FRP mechanism. When the source terminal and the destination terminal exist in the same ATM-LAN, the congestion control is performed by the FECN mechanism. Thus, in the ATM-LAN, cell loss can be suppressed upon occurrence of congestion.

Congestion control method in asynchronous transfer mode local area

An inter-network routing control method for selecting the optimum gate station in a packet network connected to another network via a plurality of gate stations. A representative gate station can be specified for each addressed network. Upon an inter-network switching call request, the switch station transfers the call request to a representative gate station, and the representative gate station decides the optimum gate station. It is possible to lighten the load on the switch station at the time of inter-network switching communication and facilitates changing the configuration of gate stations in the packet network.

Inter-network routing control method and switching network system

A packet broadcasting method broadcasts a data packet sent by a broadcasting source terminal to a number of broadcast destination terminals. A broadcasting apparatus having a peculiar DTE address is provided in a packet switching system and a broadcasting table having one or a plurality of broadcasting source terminals is defined in the broadcasting apparatus. The broadcasting apparatus registers a terminal other than a broadcasting source terminal into the broadcasting table as a broadcast destination terminal in response to a call set-up from such a terminal When the broadcasting apparatus receives a data packet from the broadcasting source terminal, a data packet having the same data as the received data packet is sent to the broadcast destination terminal.

Packet broadcasting method

In a packet switching network, in order to transmit a packet effectively, after transmission of a first packet from a source node to a destination node, a data for inhibiting a packet from being repeating to a specific trunk line from a node is set in a routing table associated with the node in accordance with a second packet received from the node. The associated routing table stores trunk lines for repeating in accordance with the destination node of the packet. The second packet represents occurrence of trouble on a transmission route for the first packet from the source node to the destination node. The transmission node includes the trunk line from the node. When the node has received a third packet directed to the destination node, the associated routing table is referred to determine a trunk line for repeating the third packet from trunk lines except for the specific trunk line in accordance with the destination node and the repeating inhibition data.

Packet switching network with alternate trunking function

A switching network having a plurality of repeater nodes, wherein each repeater node checks the number of times data packet has been received. If in excess of predetermined number, the repeater node transmits a looped trunk detection packet, the looped trunk detection packet being arranged to be written with the node address of each of the plurality of repeater nodes within a looped trunk as its repeating history. The repeater node checks whether the node address thereof is written in the repeating history or not. If the result is negative, the looped trunk detection packet is repeated and transmitted by writing the node address of the repeater node in the repeating history. If the result is positive, the repeater node does not repeat transmission of the succeeding packets from the repeater node to the route of the looped trunk, and transmits a looped trunk notification packet to repeater nodes. The looped trunk detection notification packet then forbids to repeat transmission of the succeeding packets from each of the other repeater nodes to the route of the looped trunk.

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Hadano, Japan

Atsushi Kimoto