Abstract: An apparatus and method for transferring data from a source memory to a transmit buffer memory and then from the transmit buffer memory at a particular rate. A current time counter advances at the rate at which data is to be transmitted from the transmit buffer memory to the interface. A schedule memory stores entries, each valid entry being associated with data that is to be transmitted from the transmit buffer memory to the interface. A timestamp is associated with each valid entry in the schedule memory.

Abstract: A method and apparatus for monitoring data sent between a source node and destination node in a switched network, wherein the switches configure themselves to establish a connection path to a probe switch to receive the monitored data. The source and destination are identified along with the probe switch. An originating switch on a path between the source and destination is identified and connections between the originating switch and the probe switch are established. The originating switch sends out a first message and when the probe switch receives the first message, it returns a second message to the originating switch. Each switch between the originating switch and the probe switch that receives the first and second messages configures itself to establish the connection path.

Abstract: A mechanism for avoiding the initiation of control read transactions on a system bus coupling a host system having a host memory and an interface connected to a peripheral unit as data is moved between the host system and the peripheral unit is presented. Control information associated with data memory portions in host memory is written to the interface for data memory portions storing outgoing data and data memory portions to receive incoming data. The interface includes a controller for moving data between the host memory and the interface by first obtaining the control information for the associated data portions. The interface writes status reports in association with the movement of data between the interface and the host memory via the system bus. The mechanism thus enables data transfers to occur via the system without the initiation of control reads in absence of an exception condition.

Abstract: A system for interconnecting line cards attached to a networking hub is disclosed. The disclosed system operates by forming backplane networks between the line cards using shared data path resources within the hub. Each line card attached with the hub describes its hub internal networking characteristics and capabilities. A hub management agent obtains the specific capabilities and characteristics of each line card attached to the networking hub, from each of the line cards. The characteristics and capabilities of each line card include which of the shared data path resources are accessible to the line card, and how the line card is able to operate on those accessible shared data path resources. The capabilities and characteristics of the line cards are obtained by the management agent requesting each line card for the information. The request is initiated by a triggering event, for example power-up of the networking hub or attachment of a new line card to the networking hub.

Abstract: A method for performing timer synchronization between a first processor having a first timer and a second processor having a second timer is presented. The first processor issues to the second processor a first timer value corresponding to the current value of the first timer and the second timer compares the first timer value with a second timer value corresponding to the current value of the second timer. If the second timer value is less than the first timer value, the second processor increments the second timer value to a new second timer value equal to the first timer value. If the second timer value is greater than the first timer value, the second processor issues to the first processors the second timer value and the first processor adjusts the first timer value to be equal to the second timer value.

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: Method and apparatus for creating the appearance of a network device and its communications, and in particular, an SNMP agent and its SNMP communications. A device dataset contains a plurality of counter variables having instance values which change over time and describe the behavior of the device on the network. A characterization file is created from the device dataset based on correlations among the variables and their instance values. The characterization file is used to generate predicted instance values for a simulated device.

Abstract: A network interconnection device having a router connected by a plurality of links to at least one multiport switch is presented. Each of the plurality of links is connected between one port of the router and one port of the multiport switch such that each link represents a separate path between the router and the multiport switch over which data packets may be transferred. Sets of links are defined as hunt groups, which contain multiple instances of a given resource. Each port has a forwarding engine. When a packet arrives at a router port, the forwarding engine checks if the packet destination port belongs to the same hunt group as the packet sending port. If the destination port and the packet sending port belong to the same group, the packet is sent back through the same port through which it arrived without having to pass through the router backplane, thus transferring the packet efficiently.

Abstract: A device for isolating a hazardous connection on a circuit board includes an elongated enclosure having a bore extending therethrough and a slot extending longitudinally from a first end of the enclosure. A component such as a fuse, having leads on both ends, is advanced through the bore until one of the leads, bent orthogonally to the enclosure, becomes secured in a distal end (pocket) of the slot. The length of the enclosure is determined such that when the lead is engaged in the distal end of the slot, a portion of the enclosure extends over the lead to isolate any connections made by that lead from external contact. In a preferred embodiment, a second slot is provided on the other end of the enclosure wherein a second lead may then be bent orthogonally to the device, and parallel with the first lead, to isolate both leads of the component. The protective device is advantageously transparent to allow for monitoring of the component being isolated.

Abstract: An arbitration unit contains a method of arbitration which includes distributed arbitration, a priority mechanism to support different classes of traffic, a unique arbitration ID bits for each module, a round robin arbitration within a given priority level to produce fair access to a bus 36, an arbitration timeout, and a bandwidth allocation between priority levels.

Abstract: A system and method are disclosed for routing multicast packets in a subnetwork so as to conserve bandwidth in at least some of the network segments or collision domains of the subnetwork. In particular, multicast packets are only retransmitted in the network segments that are on a path to a host that is a member of the multicast group of hosts to which the multicast packet is destined.

Abstract: A method and apparatus for substantially reducing electromagnetic radiation from a backplane used to interconnect multiple communication modules. Data signals to be transmitted onto the backplane are first scrambled using a pseudorandom code sequence, to reduce energy peaks in the radiation spectrum and to spread energy over a wider bandwidth. Signals received from the backplane are descrambled using an identical pseudorandom code sequence. Data rate synchronization is provided by recovery of a data clock signal from the received scrambled signals, and data frame synchronization is provided by transmitting data frame headers as non-scrambled data. At a receiver module, the frame headers are detected and used to reset the descrambling operation.

Abstract: Method and apparatus for determining an enforceable policy applicable to one or more network devices. The method includes attaching one or more rule elements to one or more domain elements to create policies, the domain elements representing network devices and groups of network devices, and the rule elements defining actions, a method for determining whether a conflict exists between the polices, and a method for resolving the conflicts to produce one or more enforceable policies.

Abstract: Apparatus and method for monitoring parameters that govern the operational characteristics of a network device, including the use of templates for generating configuration records of network devices of a selected model type. A database of models is provided, each model representing an associated network device and including attribute values for the parameters of the associated network device. Templates are used to screen a model in order to retrieve values for each of the attributes and create a configuration record. The configuration records may be stored in the configuration manager or other storage device, and/or transferred to the pre-existing model database for use by a network management system in reconfiguring the associated network devices. Additionally, a method and apparatus is provided that defines network groups, defines network policies for groups, determines conflicts, and resolves conflicts among groups and devices.

Abstract: In a network node having a host system coupled to a network by an adapter, VC-specific congestion is detected and reported to the host system. The host memory includes rx slots or buffers, each corresponding to one of one or more supported slot types. Per-VC slots consumed counters are maintained to count slot consumption for each active VC. Free buffer FIFOs are maintained for each of the one or more slot types, which have a predetermined congestion threshold associated therewith. Entries in each free buffer FIFO correspond to an rx slot posted by the host system. When a new rx slot or buffer in host memory is to be allocated to an incoming cell received on a given VC, the slots consumed counter is compared to the predetermined congestion threshold. If they are equal, the VC is at threshold level and the incoming cell is discarded and a report is sent to the host system.

Abstract: A status report frequency mitigation mechanism for mitigating the frequency of status report generation for raw cells during transmit operations in a network node is presented. The status report frequency mitigation mechanism operates to adjust the frequency with which status reports for raw cells are generated by manipulating the End-of-Packet (EOP) bit in transmit slot descriptors associated with transmit slots containing raw cell data.

Abstract: A bridge for simultaneous connection to n LANs, where n is greater than 2, and methods for determining whether the bridge has been connected properly. The bridge includes storage for respectively associating the (n.sup.2 -n)/2 unique pairs of LANs connected by the bridge with (n.sup.2 -n)/2 parallel bridge numbers. Messages received from a first LAN are forwarded to a second LAN only if the message identifies the second LAN and the parallel bridge number which is associated in the storage with the first and second LANs. To determine whether two or more ports of the bridge are connected to the same LAN, the bridge attempts to transmit messages from each of its ports to each other respective port by addressing the messages to the data link addresses of the other ports. After transmission, the bridge waits a short time interval and determines whether any of the messages are received at any of its ports.

Abstract: A switchable interface for conveniently coupling a network station of the CSMA/CD type to a network having any of a variety of communication media. The invention provides a single interface connector through which connection may be made directly to a twisted-pair medium, using the 10BASE-T protocol, or to a medium of a different type, through an AUI protocol and an appropriate media attachment unit. The interface connector has pin assignments chosen to minimize adverse effects of misconfiguring the station by connecting to a network having a protocol that is different from the one selected in the switchable interface. In one form of the invention, the switchable interface has the ability to determine the protocol being used by the network to which it is connected, and to switch the interface accordingly. Use of the common interface reduces station equipment cost and provides for increased user convenience, since only a single connector is needed to connect to a variety of media types.

Abstract: Apparatus and method for monitoring parameters that govern the operational characteristics of a network device, including the use of templates for generating configuration records of network devices of a selected model type. A database of models is provided, each model representing an associated network device and including attribute values for the parameters of the associated network device. Templates are used to screen a model in order to retrieve values for each of the attributes and create a configuration record. The configuration records may be stored in the configuration manager or other storage device, and/or transferred to the pre-existing model database for use by a network management system in reconfiguring the associated network devices. This system for configuration management is less time consuming, expensive, and error prone than prior systems.

Abstract: Method and apparatus providing connection-oriented services for packet switched data communications networks. Directory services include distributed discovery of MAC addresses and protocol alias addresses. Topology services include a link state topology exchange among switches, which provides each switch with a complete topology graph of the network. This enables an access switch receiving a data packet to determine a complete path from a source end system to a destination end system. Another service includes resolution of broadcast frames to unicast frames, in order to reduce the amount of broadcast traffic. Policy restrictions may be applied prior to connection setup. Path determination services enable multiple paths from a source to a destination. Connection management includes source routed mapping of connections on the desired path.