Abstract: A loop network hub port with an automatic bypass feature. The automatic bypass feature causes the hub port to enter a bypass mode upon detection of a specified loop failure initialization sequence from a node port attached to the hub port. The hub port does not propagate loop failure initialization data generated by the attached node port upon the failure of a data channel from the hub port to the node port. The hub port replaces loop failure initialization data received from the node port with buffer data and conceals the node port failure from the remainder of the loop. Upon detection of the loop failure initialization sequence received from the attached node port, the hub port enters a bypass mode and maintains that bypass mode until a recovery sequence is received from the node port. At that point, the hub port reinserts the node port into the loop.

Abstract: A method and an apparatus for isolating a communication fault within a token ring network are described. The token ring network includes a number of stations, each of which is configured to generate or repeat beaconing data indicating a network communication fault. The method requires firstly isolating each station of the token ring network in a closed-loop station ring. A location in each of these isolated station rings is then monitored for the transmission of beaconing data indicating a communication fault within the respective station ring. If the transmission of such beaconing data is not detected, the station is reconnected to the token ring network. On the other hand, should the transmission of such beaconing data be detected, the station is maintained within the closed-loop station ring. In this way, faulty stations are isolated from the token ring network.

Abstract: An apparatus and method for detecting a connection to a data transmission network functions by detecting the network signal energy on a network cable while avoiding the problems of excessive power consumption and generation of excessive electrical noise. By monitoring the receive network lines and determining if there is electrical energy on the cable in the form particular to the type of network supported by the network adapter card, the host computing device can power-down the transceiver associated with the network adapter card until an active network connection is detected.

Abstract: A transmission system for transmitting a signal from a host to a transmission medium is disclosed. The transmission system includes a current-mode digital-analog converter, an on-chip low-pass filter, a line driver, and output impedance control. Further, a method for transmitting a signal from a host to a transmission medium using on-chip filtering is disclosed. The transmission system and method can be used in transmission of Ethernet signals onto an unshielded twisted pair cable. In addition, with appropriate modification, the transmission system and method can be used for transmitting ATM or other signals onto a transmission medium.

Abstract: An electronic bus system comprises a bus wire (BW) with at least two signal transmission wires (W1, W2) and a left and a right end, which are each defined by a terminating resistor connecting the signal transmission wires to each other. A plurality of electronic control units (ECU-ECUn) are between the two ends of the bus wire (BW) connected to the signal transmission wires (W1, W2) and are adapted, via these, to transmit and receive electric signals. The bus wire (BW) is divided into a plurality of sections (S1-Sn), which are interconnected by means of connecting circuits (CC1-CCn), and forms an annular unit. Each connecting circuit (CC1-CCn) comprises relay means, by means of which each connecting circuit, coordinated with the other connecting circuits, can connect at least one terminating resistor integrated therein, in order to define the left and/or right end of the bus wire (BW).

Abstract: Distributed remote monitoring (dRMON) of network traffic and performance uses distributed nodes to collect traffic statistics at distributed points in the network. These statistics are forwarded to collectors which compile the statistics to create combined views of network performance. A collector may mimic a prior art, non-distributed, network probe and may interact with network management software as though it were a stand alone network probe thereby simplifying a user's interaction with the distributed system. The invention is designed to work in accordance with a variety of standard network management protocols including SNMP, RMON, and RMON2 but is not limited to those environments. The invention has applications in a variety of communication system environments including local area networks, cable television distribution systems, ATM systems, and advanced telephony systems.

Abstract: A hub port in a hub of a loop network which automatically bypasses a node port which is generating a particular loop failure initialization sequence. The hub port contains a detection circuit which enables the hub port to detect loop failure initialization data received from its attached node port. Upon detecting such data from an attached node port, the hub port replaces such data with buffer data to be passed to the next hub port. Upon detecting the completion of a loop failure initialization sequence from an attached node port, the hub port enters a bypass mode. The hub port no longer passes on output from its attached node port and instead forwards along the internal hub link data received from the previous hub port in the hub loop. The bypass is maintained until the hub port receives a primitive sequence indicating the recovery of the attached node port. The hub port periodically sends at least one recovery sequence to the node port.

Abstract: Method and apparatus for remote monitoring of data on a communications network, wherein data transmitted and received by a port can be examined at a location other than on the device having the examined port. A method includes the steps of selecting a mirror-from-port of a first device from which to mirror packets, selecting an analyzer port of a second device to which to mirror the packets, and mirroring the packets from the mirror-from-port of the first device to the analyzer port of the second device. The mirroring step may include establishing a connection path through the network, encapsulating the packets with a connection path identifier, and sending the encapsulated packets through the network to the second device. The benefits include ease of use, fewer resources (analyzers) needed, time savings, and not having to dedicate a physical port as the mirror-to-port on the device.

Abstract: A program debugging support device is connected to a first computer and a second computer through a network. A datagram is sent from a client program operating on the first computer to the debugging support device. At this time, the debugging support device stores the datagram from the client program in a storage unit and transfers the datagram to a server program operating on the second computer. The server program processes a datagram from the client program and sends a reply datagram to the debugging support device. The debugging support device transfers a datagram from the server program to the client program and stores the datagram in the storage unit.

Abstract: A ring data network (such as a token ring network) is divided by a security unit (1) into first and second segments (6 and 8). The second segment (8) typically corresponds to one security group in the network. Logic in the security unit reads appropriate parts of each frame (typically the two address segments) to determine whether it is appropriate to forward the frame to the next segment of the ring. If the frame does not need to go to the next segment, or is not authorized to do so, then the security unit forwards instead a modified form of the frame in which its data cannot be read (except possibly by the security unit itself). In most cases the data content of the frame will be stored in the security unit. When the modified frame returns to the security unit at its second input port (4), the original frame can (if appropriate) be reconstructed, typically by reading its data content from a store in the security unit.

Abstract: A communications network comprising N node elements operates N decision tables for controlling admission and control of data communications to the N node elements (FIG. 2). The performance of the network is optimised with respect to admission and control of commission data. Each node element generates corresponding performance data (FIG. 5), and the N decision tables and N performance data are collected at a central network controller. The network controller determines a set of new decision tables from the collected decision tables (FIG. 10) and distributes a new set of decision tables to each of the N node elements, which then proceed to operate the new decision tables throughout the network.

Abstract: Transmission and reception nodes are connected to a communication network to be controlled with respect to time according to bus time as time information shared therebetween. The transmission node periodically transmits data while keeping a predetermined free period of time. The reception node decides normality of data received. At detection of abnormality in reception, the reception node transmits during the free period of time a re-transmission request signal to the transmission node with specification of information identifying the bus time of the abnormal data reception. On receiving the re-transmission request signal, the transmission node obtains the data transmitted at the bus time identified by the information specified by the re-transmission request signal and then re-transmits the data during the free period of time to the reception node.

Abstract: In a test instrument for testing local area networks (LANs), a method for identifying network device types on a LAN operating according to the TCP/IP protocol suite using passive monitoring is provided. A test instrument is coupled to the LAN to passively receive traffic in the form of frames that are being sent between the nodes on the LAN. The frames being sent may contain information that may be uniquely associated with specific types of network devices such as servers, routers, printers. A frame processor collects and extracts the frame information from the frames, including the message type and source IP address. The frame information is compared against sets of frame types, with each set of frame types uniquely associated with one of the network device types. The device types as detected are added to a station database.

Abstract: A method of processing data from a plurality of probes which monitor traffic over a network, which includes a plurality of segments to which are connected a plurality of nodes, the method including the steps of polling the probes for monitoring data; receiving polled data from the plurality of probes; storing the polled data in a plurality of records, each of the records identifying at least a probe, a source node, a destination node, and a measure of traffic between the identified source node and destination node in that record; for a selected source-destination node pair, determining which of the plurality of probes produced a most complete report of traffic associated with that selected source-destination node pair; identifying those records among the plurality of records that designate both the probe which produced the most complete report of traffic and the selected source-destination node pair; and distinguishing within the plurality of records the identified records from the other records.

Abstract: A deficiency in a link in a messaging system is detected by sending across the link a request message that includes a coded data string, receiving across the link a reply message that includes the coded data string, and determining whether the travel time involved is excessive. To maximize the likelihood that the coded data string is included in the reply message, the coded data string is preferably included in both the subject and body fields of the request message.

Abstract: An interconnection monitoring system for use with a multiple node wired network, the system comprising a plurality of transmitters, each located at a node of the network for transmitting a transmission from the node and a plurality of receivers, each located at a node of the network, for receiving a transmission at the node, the plurality of transmitters being operative to transmit along the network a signal bearing an identification code identifying the node from which a transmission takes place, the plurality of receivers being operative to receive transmissions from a plurality of nodes, bearing the identification codes and thus indicating the interconnection status of the nodes.

Abstract: A data transfer technique in which lossy connections or temporarily interrupted network links neither prevent data transfer nor substantially impair the ease with which a user can transfer data. A sender is advised of receivers on a network that are available to receive data over the network. Also, while data transfer from a sender to a receiver is being performed, the availability of the receiver is monitored. If, during the data transfer, the receiver becomes unavailable to receive the data, then the data transmission stops and the sender is informed that the receiver has become unavailable. The sender continues to monitor the network to determine if the receiver has regained its availability. If the receiver regains availability, the sender is able to automatically resume the data transmission, provided the availability is regained before the network connection is completely lost. The invention is useful for wireless networks as well as wired networks.

Abstract: The present invention automatically monitors a Data Center Operations (DCO) network (or any LAN/WAN network) for circuit outages and sends a notification if an outage is detected. A console at a Remote Operations Center periodically pings a console at each Data Center (pinging may also be on-demand). The remote console receives responses from each pinged Data Center console. A response will be received for each possible route between the Data Center and the Remote Operations Center. These responses will indicate the route that was taken. The routes indicated in the responses are then compared with a table of routes previously identified as routes of concern or interest. Also listed in this table is a circuit identifier for each route. Any route listed in this table for which a response was not received is identified as unavailable. An automatic notification, such as a page, is then sent identifying this route by the circuit identifier.

Abstract: A system and method are disclosed for acquiring network performance data. A mission server is connected to a network, and is operative to interface with Clients to define and receive requests for a mission. The mission as defined includes operations that require participation in the network by devices connected to a plurality of segments at a plurality of locations within the network. A plurality of sentries are provided on devices connected to the segments of the network at locations within the network so that the devices are operative to participate in the network from the segments of the network at their locations. The sentries are then operative to support the mission by participating in the network through the devices. A request for a mission is received at the mission server and the mission is communicated from the mission server to the sentries required to execute the mission.

Abstract: A system and method monitor and control an Ethernet local area network, by monitoring bit gap distances between adjacent frames communicated by stations on the local area network. By analyzing the number of events for pre-selected bit gap distances, the network traffic characteristics can be characterized and interconnection paths between stations in the network can be altered.

Abstract: A method implemented in a computer network supports a number of client-server sessions from a protocol stack having a single physical adapter associated therewith. The method begins by associating at least two logical adapters to the physical adapter, with each of the logical adapters being adapted to handle a predetermined subset of the number of sessions. Sessions are then allocated to the logical adapters in a sequential manner. In particular, the sessions are allocated to a first logical adapter until the predetermined subset of the number of sessions for that adapter is reached, whereupon the sessions are allocated to a second logical adapter. Each session is associated with a pair comprising an identifier for the logical adapter and an entry in an associated table, with the table entry being a socket number. Communications are "routed " through the physical adapter and the logical adapters by associating socket numbers with logical adapter/session number pairs.

Abstract: An improved system and method for monitoring a fieldbus network. The improved method and monitor utilize multiple filters with the capability of simultaneously capturing packets from more than one fieldbus and the ability to apply multiple filters to any single fieldbus. Filtered packets are captured as capture documents and stored in the monitor's memory storage. Filtered packets can be displayed, in real time, on the monitor's display screen. The improved monitor is configured to perform post-capture filtering of captured packets. Post-capture filtering does not destroy data. The improved monitor permits dynamic altering of filter settings. Using this feature, the user can initiate capture using a first filter settings, alter the filter setting while packets are being captured, and apply the altered filter setting to the fieldbus without terminating capture.

Abstract: There is provided a communication control method for a network including duplexed ring transmission lines and a plurality of communication controlling devices each accommodating a plurality of terminals and adapted to transmit data sent from any of the terminals and receive data over the ring transmission lines, the communication control method comprising the steps of: causing one communication controlling device to transmit monitoring cells simultaneously over the duplexed transmission lines, the monitoring cells each including a pass indication area for retaining a source address and identification information for identifying a passed communication controlling device; and causing another communication controlling device which receives the monitoring cells respectively from the duplexed transmission lines to relay and circulate the monitoring cells respectively over the duplexed transmission lines after writing in the pass indication area of each of the received monitoring cells data indicative of passage of

Abstract: A multiplexed network connecting apparatus comprising, communication lines for connecting in parallel a pair of LANs, relay stations each interposed between each of the communication lines and each of the LANs, transmission means for transmitting a transmission frame from a first LAN of the LANs to a second LAN, and bypass transmission paths each for connecting the relay stations. One of the first relay stations connected to the first LAN, which is designated as an operation system relay station, receives the transmission frame from the first LAN, transfers the transmission frame to the second LAN through the communication line connected to the operation system relay station, and transfers the transmission frame to another of the first relay stations, which is designated as a standby system relay station, through the bypass transmission path when the communication line connected to the operation system relay station malfunctions.

Abstract: A circuit arrangement disposed in a node within a local area network is connected to a communication bus within the local area network. The circuit arrangement includes an input circuit for introducing data from the communication bus into the node. A node state detecting device is operative for detecting whether or not the node is in a stand-by state. A power feed suspending device is operative for suspending power feed to at least part of the input circuit when the node state detecting device detects that the node is in the stand-by state. A power feed restarting device is operative for monitoring a voltage at the communication bus, and restarting the power feed to at least part of the input circuit when the voltage at the communication bus becomes equal to a level indicating reception of data. A protective circuit is operative for protecting the input circuit from an abnormal current which flows from the communication bus.

Abstract: Simultaneous events reported to an equipment management system are compared with historical data in order to establish whether there is a relationship between the events. Historical data is used to determined the statistical probability of the events occurring independently simultaneously. If this probability is below a predetermined threshold this will suggest that the events are not independent, but are relaxed. Such relationships are alerted to an operator, for example by highlighting or grouping on a screen display, assisting the operator in identification of related events, without the need for prior knowledge of the relationships in the system. The events may be alarms generated by faults in a network. The identification of related faults at different points in the network assists identification of their common cause.

Abstract: An apparatus for detecting errors in a wireless communication channel comprises a receiver which receives a data stream from the wireless communication channel, a signal strength indication circuit coupled with the receiver which indicates signal strength for a received data stream, and processing resources coupled to the signal strength indication circuit which monitors the received data signal strength to detect anomalies in the strength of the received data stream, typical of erroneous data. Also, the system includes a signal phase monitoring circuit coupled with the receiver. This circuit indicates phase of the received data stream. Processing resources coupled with the signal phase monitoring circuit, monitor the received data stream phase to detect anomalies in phase of the received data stream typical of erroneous data. In addition, the data stream will include data packets having error detection codes imbedded within the data packets.

Abstract: A method and apparatus for providing a plurality of digital devices, including protocol analyzers, work stations, cable testers, and the like, with a data signal received from one of a plurality of target networks is. A plurality of data ports, including at least one target data port, a plurality of device data ports, and a plurality of intermediate data ports. Data channels establish a plurality of device data paths between a plurality of digital devices and a corresponding plurality of device data ports and a target data path between one of the target networks and at least one of the target data ports. A switch establishes a first data path between any selected one of the plurality of target data ports and a respective first intermediate data port. A replicator replicates a first data signal from the first intermediate data port at least to a second intermediate data port and to a third intermediate data port.

Abstract: A method in a LAN test instrument for detecting proxy ARP agents and misconfigured routers in a TCP/IP LAN is provided. The method first allows for detection of routers running proxy ARP for the default route by issuing a single ARP command for a unique remote host. Because the target IP address chosen as a unique, non-existent device, the router will respond to the ARP request with a proxy ARP reply for its default route if this function is enabled. The method further allows for distinguishing between responses from actual devices having duplicate IP addresses and responses from misconfigured routers replying in proxy ARP for local hosts. The false duplicate IP addresses due to proxy ARP replies may be identified as phantom entries in a data base that can then be appropriately tagged or eliminated to display only the entries that correspond to actual physical devices to the user of the LAN test instrument.

Abstract: A new leader of a group of processors executing within a distributed computing environment is selected when the current group leader fails. The new group leader is selected from a membership list ordered in sequence of joins of processors to the group of processors. The selected leader is the next processor on the membership list after the failed group leader. In particular, it is the next active processor on the membership list. The group of processors is informed of the new group leader, after it is selected.

Abstract: A new leader of a group of processors executing within a distributed computing environment is selected when the current group leader fails. The new group leader is selected from a membership list ordered in sequence of joins of processors to the group of processors. The selected leader is the next processor on the membership list after the failed group leader. In particular, it is the next active processor on the membership list. The group of processors is informed of the new group leader, after it is selected.

Abstract: A new leader of a group of processors executing within a distributed computing environment is selected when the current group leader fails. The new group leader is selected from a membership list ordered in sequence of joins of processors to the group of processors. The selected leader is the next processor on the membership list after the failed group leader. In particular, it is the next active processor on the membership list. The group of processors is informed of the new group leader, after it is selected.

Abstract: A technique is disclosed for sending alarm information to a network management station from at least one of a plurality of network stations wherein an unusual event(s) has occurred. The network stations are located in a wide area network and are managed by the network management station using a control path. An occurrence of an unusual event is detected in the at least one of the plurality of network stations. Following this, alarm information is generated in the network station wherein the unusual event has occurred. The alarm information includes address information for specifying the network station. Subsequently, the alarm information is sent using an alarm path, which is dedicated to transmission of the alarm information, to the network management station.

Abstract: Designed such that in systems comprising a plurality of transmission devices and transmission lines connecting the transmission devices, transmission line fault data indicating fault event conditions on transmission lines is circulated among the transmission devices and when a fault is verified on a connecting transmission line, verified transmission line fault data is appended by the transmission devices to the input transmission line fault data for output.

Abstract: In a ring network system formed by a plurality of nodes connected to one another through a ring-shaped path, each of the nodes collects all of node information signals representative of states of the nodes and memorizes the node information signals in a node information signal memory included in each node. The node information signal is periodically transmitted to each node from an adjacent one or ones of the nodes through the ring-shaped path and is renewed from time to time. Such collection of all of the node information signal in each node makes it easy to check an alarm by a superintendent.

Abstract: In a ring network system comprising a plurality of nodes, each node is provided with a node information table which is logically divided into node areas each corresponding to a single node within the ring network. Each node collects node information stored in the node information tables of the two adjacent nodes by regularly accessing the node information tables of those nodes, and updates the contents of its own node information table. As a result of the above information collecting operation that is performed by each node, all the node information can be stored in the node information table of each node.

Abstract: A portable tester for local area networks comprising a AUI circuit coupled to a media specific transceiver, a battery, a push-to-test switch and four light emitting diodes and an RJ45 jack for each of a personal computer and a network hub. When the push-to-test switch is pushed, power is applied to the media access unit and a link pulse is generated for coupling via a PC jack to a personal computer plugged into that jack. The link pulse is also coupled to any network hub plugged into a hub jack. The PC and network hub cannot both be simultaneously connected. If whichever unit is connected receives the link pulse and generates its own link pulse which is received by the tester, a link status LED is lit green. Otherwise, it is left dark. If the unit connected outputs a data packet in response to receipt of the link pulse, a receive data LED is lit green. Otherwise, it is left dark. If the link pulse is positive-going on the correct line, a polarity LED is lit green. Otherwise, it is left dark.