Fujitsu Corporation

Fujitu Limited

Eiji Sugawara

Atsushi Suzuki

Noboru Nakama

Hideyuki Motoori

Katsuya Kitamori

Kenya Takuwa

Naoyuki Kato

A packet transport network system includes a first node to transmit a control packet through a secondary port, when the first node does not periodically receive, through a primary port, a continuity check packet transmitted on the first MLSP set in the first direction; and a second node, when the second node receives the control packet through a secondary port, to relay or terminate packets on the first and second active MLSPs, to receive, through the primary port, the multicast packet transmitted on the second MLSP set in the second direction, and to bridge the received multicast packet to a recovery path set in an interested link, the second node periodically receiving, through a primary port, the continuity check packet transmitted on the second MLSP set in the second direction, wherein the first node receives, through the second port, the multicast packet bridged to the recovery path.

Packet transport network system

A ring network of a multicast label switch path scheme includes a transmitting node and receiving nodes connected to form a ring. A signal input to the transmitting node is branched to be transmitted in first and second different directions to first and second receiving nodes through first and second working paths, respectively, in the ring network. The first and second receiving nodes define terminal points of the first and second working paths, respectively, from the transmitting node. A first backup path is set from the first receiving node to the transmitting node, and a second backup path is set from the second receiving node to the transmitting node. The first backup path is in an opposite direction to the first working path and the second backup path is in an opposite direction to the second working path.

Network and fault recovery method

A method for packet forwarding, including receiving packets; extracting a test packet containing information indicating a path to be verified from the received packets; and forwarding the test packet to the path to be verified, rather than to a first path to which the received packets are forwarded, based on the information indicating the path to be verified contained in the test packet.

Apparatus and method for packet forwarding

A communication network system includes a processor, and a plurality of node apparatuses using a protocol to establish paths therebetween, wherein the processor determines each of the node apparatuses to be a packet source or a packet destination, and operates to detect an occurrence of failure in two paths being established between the packet source and the packet destination in the communication network system, and wherein the processor transmits packet data including user data through one of the two paths, and when one of the node apparatuses detects an occurrence of a failure in one of the two paths, the processor changes the path to the other path.

Communication network system, data transmission method, and node apparatus

An optical transmission apparatus connected to an optical ring network stores identification information of an optical transmission apparatus as a communication partner predetermined on a communication path. Each optical transmission apparatus includes self identification information in header information of an optical signal having a working wavelength used in normal operation, and transmits the optical signal to one of the two optical ring networks transferring optical signals in mutually opposite directions. The optical transmission apparatus determines whether the identification information included in the header information of the received optical signal having the working wavelength matches pre-stored identification information. The optical transmission apparatus thus detects a fault that occurs by the communication path. The optical transmission apparatus having detected the fault requests the communication partner to transmit the optical signal on a backup wavelength in the optical ring network opposite in direction to the optical ring network in the normal operation.

Optical ring network system

A system enabling inter-ring network connection when a plurality of ring networks are connected via a redundancy network, that is, a packet network system configured by a plurality of ring networks and redundancy networks linking the plurality of ring networks. This system virtually defines a plurality of virtual resilient packet ring networks among all of these packet networks and transfers packets on a designated virtual resilient packet ring network. Here, each virtual resilient packet ring network is identified by a virtual resilient packet ring network identifier allocated to each.

Packet network system

A path switching ring control apparatus is provided for use in a synchronous (SDH) network, and in particular for the purpose of repairing a fault which occurs in an asynchronous (PDH) subnetwork contained therein, this apparatus having a transmission alarm detection section which monitors the input PDH signal and generates a transmission alarm signal when a degradation of the quality thereof is detected, a path overhead generation section which generates the path overhead information of the transmission alarm signal from the transmission alarm detection section, and a path overhead insertion section which inserts the overhead information generated by the path overhead generation section into an SDH signal after the mapping thereof.

Path switching ring control apparatus in a synchronous (SDH) network

A communication system includes a first data processing unit, a second data processing unit, and a data link line provided between the first data processing unit and the second data processing unit. A first monitor terminal controls the first data processing unit and monitors the first and second data processing units. A second monitor terminal controls the second data processing unit and monitors the first and second data processing units. A first switching circuit is coupled to the first data processing unit, the first monitor terminal and the data link line, and selectively connects two of the first data processing unit, the first monitor terminal and the data link line. A second switching circuit is coupled to the second data processing unit, the second monitor terminal and the data link line, and selectively connects two of the second data processing unit, the second monitor terminal and the data link line. The first switching circuit has a mode in which the first terminal is connected to the data link line and the second switching circuit has a mode in which the second data processing unit is connected to the data link line so that the first monitor terminal monitors the second data processing unit.

Communication system having two opposed data processing units each

A method and apparatus for detecting the presence or absence of errors caused along a designated section of a virtual path established within a communication network. The number of errors is detected at both the entrance and exit of a detection section. The number of errors detected at the entrance is transmitted to the exit by using a path overhead of a virtual path to be monitored, and the number of errors at the entrance is subtracted from the number of errors at the exit, thereby calculating the number of errors caused along the detection section. The path overhead containing data on the detected error count includes a parity compensation bit that is set so that the parity carried in the path overhead remains unchanged. This eliminates the need to recalculate bit interleave parity-2 for the virtual path under monitoring.

Tandem connection maintenance system

A real time clock synchronizing system, provided in each of a plurality of network elements in a synchronous transmission network, comprises: a generating unit for generating, based on a reference clock, self-generated real time information indicating a real time of the network element. The system also includes an extracting unit for extracting reference real time information contained in an overhead area of synchronous signals received by the network element. A selector unit selects as a reference real time information to be transmitted from the network element, one of the self-generated real time information and the reference real time information extracted by the extracting unit. A transmitting unit contains the reference real time information selected by the selector unit, in an overhead area of synchronous signals to be transmitted from the network element.

System for synchronizing real time clock by transmitted real time

A subscriber apparatus having working ringer generators and a standby ringer generator which is alternately used when there is a fault, wherein provision is made of a traffic monitoring unit which continuously monitors the traffic of calls terminating at the subscriber lines and a ringer switching unit which switches a working ringer generator to a standby ringer generator when it is judged that the number of the terminating calls exceeds an allowable number, whereby the apparent capacity of the working ringer generators is increased.

Subscriber apparatus with ringer generator for sending ringer signal to

A line interface circuit on the receiving side detects communication failure in terms of an error rate and informs the supervisory and control unit on the receiving side of the occurrence of the failure. The supervisory and control unit on the receiving side in turn switches the line data communications from the receiving side to the transmitting side to another line unused for data communications to inform the supervisory and control unit on the transmitting side of the occurrence of the failure. The supervisory and control unit on the transmitting side switches the line for data communications from the transmitting side to the receiving side to the other line. The switching circuit on the receiving side comprises buffers each inserted in a line and a buffer connected to the common outputs of the buffers so that the supervisory and control unit on the receiving side automatically receives a transmit signal transmitted over a line switched on the transmitting side.

Data link protecting system

A supervisory system for a primary group digital transmission line wherein a terminal repeater transmits, over a supervisory line, address information designating an intermediate repeater and line within the intermediate repeater to be monitored while the line is in a normal, in-service condition. The terminal repeater and intermediate repeaters are cascade connected by way of the supervisory line. The terminal repeater and each of the intermediate repeaters include amplifiers that receive and send information along the transmission line, and have a monitor output. The monitor output is processed by an error monitor within the terminal repeater and in each of the intermediate repeaters and the results of the error monitoring provided to the supervisory line in response to polling by the terminal repeater.

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Kawasaki, Japan

Eiji Sugawara