Nec Corporation

Zhenlong Cui

Kazuo Takagi

Masaki Umayabashi

Akira Sakurai

Hiroyuki Takagi

Atsushi Iwata

Hideo Yoshimi

Hiroshi Tanaka

Nobuyuki Enomoto

Ryuichi Ikematsu

A communication device communicates with a counterpart device via a working path or any of a plurality of backup paths. The communication device includes: a plurality of selection units which select either one of two paths, the plurality of selection units including a main selection unit and an auxiliary selection unit being different from the main selection unit; and a path determination unit which determines a path selected by one of the plurality of selection units which has last performed path selection to be a path to be used for communicating with the counterpart device. The main selection unit selects one path from between the working path and one of the plurality of backup paths. The auxiliary selection unit selects one path from between a path selected by one selection unit of the plurality of selection units and one of the plurality of backup paths, the one selection unit being different from the auxiliary selection unit.

Communication device, communication system, method for determining path, and program

A transmission source node transmits diagnostic frames where a TTL value is set to the number of hops that is counted until an intermediate node. A relay node decrements the TTL value of the received diagnostic frames, counts the number of diagnostic frames where the decremented TTL value is 0, and recognizes continuity between the transmission source node and the relay node based on the number of transmitted diagnostic frames transmitted from the transmission source node and the number of diagnostic frames where the decremented TTL value is 0.

Diagnostic system

The present invention measures 1-way delay without equipping all nodes with special functionality in a situation in which time has not been synchronized. The delay measurement system of the present invention has a transmission origin node and a transmission destination node which is connected to the transmission origin node through a network including relay nodes, and measures the delay time from the transmission origin node to the transmission destination node direction, wherein the transmission origin node generates a clock. On the basis of the generated clock, delay measurement packets are generated at regular periods. The generated delay measurement packets are transmitted to the transmission destination node. The transmission destination node selects the delay measurement packets from among the received frames. The delay received by the delay measurement packets in the network between the transmission origin node to the node itself is measured.

Delay measurement system and delay measurement method, as well as delay measurement device and delay measurement program

A node according to the present invention is used in an MPLS (Multi Protocol Label Switching) network, and the node includes an input unit which receives an OAM (Operation Administration and Maintenance) frame including TTL (Time To Live) from outside of the node and an output unit which transmits an OAM frame to outside of the node, wherein the input unit sets the TTL to a specific value and transmits the received OAM frame to the output unit in case a termination destination which an OAM frame received from outside indicates is the node and the received OAM frame is to be transmitted to the output unit and the output unit terminates an OAM frame transmitted from the input unit.

Node, a monitoring management method used for a node, and a transfer system, an input circuit and an output circuit

A communication apparatus comprises: a memory unit which correlates a label assigned to a packet and an address of a source of the packet, and memorizes them as an entry; a receiving unit which receives a packet from a network; a learning unit which judges whether or not there exists an entry corresponding to the received packet in the memory unit, and in case there exists no entry corresponding to the received packet in the memory unit, stores a label assigned to the received packet and an address of a source of the received packet in the memory unit; and a processing unit which, in case there exists an entry corresponding to the received packet in the memory unit, assigns an address corresponding to the received packet to the received packet.

Communication using MPLS-ARP messaging

An inspection signal to inspect forward-path or return-path communication, is transmitted from a reference node of a network. A response signal is transmitted in a priority class from a node of a forward path to the reference node. In the case of inspection of return-path communication, a replica of the response signal is transmitted in a non-priority class from the node of the forward path to the return path, and the node that receives the replica of the response signal transfers the replica in a priority class to the reference node. In the case of inspection of forward-path communication, a replica of the inspection signal is transmitted in a non-priority class from the node of the forward path to the forward path, and a replica of the response signal is transmitted in a priority class from the node that receives a replica of the inspection signal to the reference node.

Congestion detecting method and communication node

A clock synchronization system synchronizes a clock of a slave node with a clock of a master node. The master node includes a packet transmitting unit that transmits a packet including a time stamp (TS) to the slave node. The slave node includes: a packet receiving unit that receives the packet transmitted from the master node; a packet filter unit that calculates as a value of delay of the packet a difference between a TS on the clock of the slave node when the packet is received and the TS of the packet received, corrects the value of the delay of the packet or a threthold for the delay of the packet, and performs filter processing on the packet received from the packet receiving unit based on the value of the delay of the packet and the threshold for the delay of the packet; and a phase synchronization unit that outputs the clock of the slave node based on the TS included in the packet employed.

Packet filter-based clock synchronization system, apparatus, and method, and program thereof

Between a first pair of termination nodes, a first current-use packet transmission path and at least one first spare packet transmission path are defined. Between a second pair of termination nodes, a second current-use packet transmission path and at least one second spare packet transmission path are defined. When no network fault occurs, packets are transmitted between the pairs of nodes in a 1:1 transfer mode in which the pairs transfer packets via both current-use packet transmission paths only. When a network fault occurs in the first current-use packet transmission path, both transmissions are switched from a 1:1 transfer mode to a 1+1 transfer mode, in which the first pair of nodes transfer packets by using the first current-use packet transmission path and the first spare packet transmission path, and the second pair transfer packets by using the second current-use packet transmission path and the second spare packet transmission path.

Packet transmission system and fault recovery method

An exemplary object of the present invention lies in a point of providing a technology capable of measuring a transmission quality of an Ethernet network in order to utilize Ethernet as carrier-grade communication. The present invention includes an error bit number measurer for measuring the number of error bits that have occurred for a frame of Ethernet, being a target of monitoring, within a monitoring period, a transmitted bit number measurer for measuring the number of total transmitted bits of Ethernet frames that a device facing it has transmitted within the foregoing monitoring period, and a bit error rate operator for obtaining a bit error rate of a transmission path by employing a measurement result by the foregoing error bit number measurer and the foregoing transmitted bit number measurer.

Quality measuring system, quality measuring apparatus, quality measuring method, and program

The clock synchronization accuracy between a master node and a slave node is stably measured. The slave node synchronizes its own clock with the clock of the master node by means of the packets transmitted from the master node. It reproduces the clock of the slave node by means of the transmitted packets, accumulates information on the transmitted packets and the clock of the slave node and performs clock synchronization on the basis of the accumulated information.

Clock synchronization system, its method and program

An object of the present application is to provide a technology that can achieve packet communication between terminals connected to the Internet by way of a relay server in a faster and safer manner. The system of present application is a communication system characterized in that, on receipt of a start-connection message, a relay server having the lowest load is searched, and communication is achieved by way of the relay server found.

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Tokyo, Japan

Zhenlong Cui