Abstract: Apparatus and method for receiving alarms from multiple network management servers and applying a plurality of policy-based filters to the alarms. The filters may be named and stored in a database, and application of the policy-based filters may be scheduled for different times. The same policy-based filters may be applied to one or more multiple network management applications. The invention allows greater control over which alarms get reported to network management applications and provides a means to ensure consistency of reported alarms across multiple network management applications.

Abstract: An intermodule network bus architecture using only two bus wires to transmit data and module state information. A two-pin bus interface in each network module connected to the bus provides for a distributed arbitration procedure in the event that two or more modules are competing for bus access, and provides a coding scheme under which both data signals and collision announcements are transmitted from module to module through the two-wire bus. The architecture handles multiple distributed repeater modules, as well as other network components such as bridges and routers connected to the same bus. An important aspect of the invention is that multiple bus interfaces function as a distributed state machine, to handle the arbitration process and to provide a consistent framework for detecting and processing data signals and various types of collisions, including receive collisions detected on a single local module port, and transmit collisions involving activity on multiple local ports of one or more modules.

Abstract: Apparatus and method for receiving alarms from multiple network management servers and applying a plurality of policy-based filters to the alarms. The filters may be named and stored in a database, and application of the policy-based filters may be scheduled for different times. The same policy-based filters may be applied to one or more multiple network management applications. The invention allows greater control over which alarms get reported to network management applications and provides a means to ensure consistency of reported alarms across multiple network management applications.

Abstract: A method and apparatus for forwarding variable-length packets between channel-specific packet processor in a crossbar of a multiport switch involve segmenting variable-length packets into fixed-length payload segments and multiplexing the payload segments with response or request data to form fixed-length switching blocks. The fixed-length switching blocks are transferred to and from the crossbar over respective input and output connections in order to minimize the number of connections between the packet processors and the crossbar. The input and output connections enable the transfer of a current packet through the crossbar while supplying the crossbar with request information necessary to schedule subsequent packets through the crossbar. In a preferred embodiment of the invention, packets are timed to pass through the crossbar one after another in order to utilize the maximum bandwidth of the crossbar.

Abstract: A network management system includes a user interface, a virtual network and a device communication manager. The virtual network includes models which represent network entities and model relations which represent relations between network entities. Each model includes network data relating to a corresponding network entity and one or more inference handlers for processing the network data to provide user information. The system can poll or communicate with certain network entities and can infer the status of network connectors and other network entities for which polling is impossible or impractical. The system performs a fault isolation technique wherein the fault status of a network device is suppressed when it is determined that the device is not defective. User displays include hierarchical location views and topological views of the network configuration.

Abstract: An apparatus controls the transmission rates of a plurality of end stations in a computer network, and the network has at least one intermediate node. The intermediate node has a plurality of virtual circuits passing therethrough, where the virtual circuits are established between the end stations. The end stations transmit data packets at a plurality of discrete transmission rates. The end stations transmit data packets containing a field having transmission rate information. The intermediate node reads the transmission rate information for the virtual circuits, by the intermediate node detecting the transmission rate information in the field of a data packet which it receives. The intermediate node counts the number of virtual circuits using each of the discrete transmission rates. The intermediate node maintains an indication that a selected virtual circuit has been counted, and for not counting the virtual circuit more than once during a switch time interval.

Abstract: A method and apparatus for controlling the flow of variable-length packets to a multiport switch involve accessing forwarding information in a memory based at least partially on layer 4 information from a packet and then forwarding the packet only if the packet is within a bandwidth consumption limit that is specified in the forwarding information. In a preferred embodiment, a credit bucket algorithm is used to ensure that packet flows are within specified bandwidth consumption limits. The preferred method for implementing the credit bucket algorithm to control flows of packets involves first receiving a particular packet from a flow and then stripping the layer 2 header information from the packet. The layer 3 and layer 4 information from the packet is then used to look-up flow-specific forwarding and flow control information in a memory that stores a linked list of table entries that includes the fields necessary to implement the credit bucket algorithm.

Abstract: The input bandwidth of a data transfer device is increased by altering the conventional memory arbitration method in which a data cell is stored and a data cell is forwarded during each data transfer cycle. The input data rate is monitored and when the input data rate exceeds the maximum average throughput of the memory, the outcome of the memory arbitration cycle is changed so that the memory arbitration cycle consists of two stores (memory write operations) instead of one store and one forward (memory read operation.) In effect, the input memory arbitration process steals cycles from the output memory arbitration process when the input load exceeds that of the maximum average memory throughput. In accordance with one embodiment, the input data rate is monitored by examining input port FIFO buffers for the presence of data cells waiting for storage.

Abstract: An input-buffered multipoint switch having input channels and output channels includes multi-level request buffers, a data path multiplexer, and a scheduler. The switch has a distinct multi-level request buffer associated with each input channel and each request buffer has multiple request registers for storing data cell transfer requests of different priorities. The multi-level request registers are linked in parallel to the scheduler to allow arbitration among requests of different input channels and different priority levels. The preferred arbitration process involves generating masks that reflect the output channels required by the same priority level requests. Utilizing masks to arbitrate between multiple requests in an input-buffered switch reduces arbitration cycle time and minimizes HOL blocking.

Abstract: An apparatus and method for receiving time skewed data from a parallel data bus. A data transfer on the parallel data bus is preceded by a start-of-cell delimiter consisting of a predetermined sequence of pulses on each of the data signals. The data is received from the bus by receive logic employing a local clock. Sampling logic is used to sample each of the data signals received from the bus at a rate which is higher than the local clock rate. Sample registers store a plurality of samples of corresponding data signals, the number of samples stored being large enough to store at least some of the pulses constituting the start-of-cell delimiter. Start-of-cell detect and center select logic is used for determining that a start-of-cell delimiter is stored in each of the sample registers, and for determining which of the samples stored in each of the sample registers represents the approximate center sample of one of the pulses of the start-of-cell delimiter.

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 system and method for controlling access to a shared object among a plurality of interconnected processes. A lock token is associated with a shared object. In order for a process to access or modify the associated object, it must possess the lock token. Whenever a process establishes control of the lock token, it transmits a message to each other process indicating that the process controls the lock token. In some instances, in order for a process to establish control of the lock token, the process must receive approval from each other process. Further, when two or more processes request the lock token at the same time, neither process will gain control and each process will then wait for a random time period before again seeking control of the token.

Abstract: Control of network surveillance in communications networks is accomplished by dividing the surveillance task into two sub-tasks. The first sub-task automatically identifies communications within the network which are to be monitored. Such identification is accomplished by the application of a reasoning system to data received from the network. The identification of the data to be monitored is received by the second sub-task along with network topology information. The second sub-task also applies a reasoning system to this data in order to configure probes and switches within the network so that the identified data can be captured.

Abstract: Aspects of the invention include a method of conducting a reduced length search along a search path. A node which would otherwise occur between a previous and a following node in the search path is eliminated, and information is stored as to whether, had said eliminated node been present, the search would have proceeded to the following node. During the search, a search argument is compared with the stored information, and the search effectively progresses from the previous node directly to the following node if the comparison is positive. In preferred embodiments, some nodes provide result values for the search, and a node is eliminated only if its presence would not affect the result value for the search. In another aspect, the invention features a method of conducting a two mode search of reduced length. For a first mode of the search, nodes along a search path are provided, at least some of the nodes including one or more pointers pointing to other nodes.

Abstract: Method and apparatus for automatically populating a network simulation tool database with network topology and/or traffic information. A topology extraction tool is provided for reading the topology and traffic information in a network management system database, and translating this information into a matching data format required by the simulation tool database before writing the information to the simulation tool database. This automatic method avoids the time-consuming and error-prone prior art manual method of constructing a network model.

Abstract: A network interface for receiving both high speed signals and low speed signals includes a passive filter manufactured entirely from passive electronic elements. The filter filters the low speed signal when a low speed signal is received, and does not distort a high speed signal transmitted to an encoder/decoder device when a high speed signal is received.

Abstract: A system for controlling power application to an electronic component during a hotswap operation. A chassis contains a plurality of slots for interfacing with electronic components, each slot having an associated timing device. The electronic component contains a delay mechanism, such that when the electronic component interfaces with a slot in the chassis, the delay and timing mechanisms interact to create a slot timing circuit. The slot timing circuit interfaces to a ramp-up switching circuitry to produce a controlled application of power to remaining circuitry of the electronic component. The timing mechanism may be a resistor and the delay mechanism may be a capacitor, such that an RC circuit is formed which controls, in a time delayed fashion, a switching mechanism which in turn controls ramp-up of power application to the electronic component.

Abstract: A repeater which introduces a minimum of delay in the transfer of a data packet from a source LAN to a destination LAN has an arbiter which grants access to a bus for a port to broadcast a received data packet onto the bus for loading the data packet into a transmit buffer for each outgoing port. The arbiter grants access only after all ports signal that their transmit buffers are ready to load the data packet from the bus. A transmit buffer signals that it is ready to be loaded at the passage of the collision window as it is transmitting a packet previously loaded into the transmit buffer. Accordingly, the transmit buffer is simultaneously transmitting the previously loaded packet and loading the new packet after the arbiter responds to the signal.

Abstract: Availability of a computer network is determined by analyzing specific pairs of source/destination devices in the network and alternative paths between them. The topology of the network is analyzed so as to determine all paths between the devices and the availability of devices on each path is determined. If any one alternative path is available, this is included in the determination of network availability. Further, a relative weight may be assigned to various devices/paths on the network depending on usage or other parameters. The availability information is then presented in the format of a report card where specific source/destination pairs and the paths therebetween are chosen as indicia of the network's availability.

Abstract: A method and apparatus for routing packets through a multiport switch involves attaching indicators to packets before the packets are passed through a switch fabric, and then using the indicators to look-up output port vectors after the packets have been passed through the switch fabric. In a preferred embodiment of a 64.times.64 port switch, an 8-bit output channel vector and a 15-bit output port index are attached to a packet and passed through the switch fabric. The 8-bit output channel vector directs the packet to the proper output packet processor(s) and the 15-bit output port index is used to look-up an output port vector that identifies the output port(s) that will receive the packet. The method and system provide low packet overhead and flexible scaling.