Abstract: A technique for synchronizing run-length-limited data transmitted over two parallel narrowband communication channels, such as in a token ring local area network using fiber distributed data interface (FDDI) protocols. A serial data stream to be transmitted is demultiplexed onto the two channels by sending sequential blocks of equal numbers of bits over alternate channels. In a receiver-multiplexer, block boundary synchronization is established during connection initialization by using a property of a required HALT code to detect block boundaries received in each channel. Skew compensation is effected by comparing the times of detection of the block boundaries in the two channels, and appropriately controlling a variable delay in at least one of the channels.

Abstract: A technique for controlling access to a bridge connected to at least two networks, such that network collisions are reduced, transmit live-lock conditions are eliminated, and buffer memory requirements are minimized. For at least one target network of the two networks, two dynamic lists are maintained, to keep track of data packets received from the target network and not yet forwarded, and to keep track of data packets stored for forwarding to the target network, but not yet forwarded. The target network uses a half-duplex medium and a CSMA/CD (Carrier Sense Multiple Access with Collision Detection) protocol. The invention operates by dynamically adjusting an inter packet gap (IPG) betweens data packets forwarded to the target network, such that stations on the target network are, under selected conditions, given an extended opportunity to transmit.

Abstract: Method and apparatus for scheduling operations of a network adapter in such a way as to minimize latency in processing received data packets, while still guaranteeing time for processing necessary background tasks. The method includes executing a polling loop in which repeated tests are made for the presence of receive data to process, but only a limited amount of receive data processing is performed before checking for background processing that needs to be performed. The polling loop ensures that immediate attention is given to processing of receive data, without the inherent latency of interrupt processing, but still gives periodic opportunities for background processing. Background processing is performed for a guaranteed minimum processing time before permitting a return to receive processing. Background processing may be performed without a guaranteed minimum processing time, but only when there is currently no receive processing to do.

Abstract: A packet data communication network employs a local switch, router or bridge device functioning to transfer packets between segments of a larger network. When packets enter this device, an address translation is performed to generate local source and destination addresses which are much shorter than the globally-unique addresses contained in the packet as dictated by the protocol. These local addresses are inserted in a header that is added to the packet, in addition to any header already contained in the packet. This added header travels with the packet through the local switch, router or bridge device, but then is stripped off before the packet is sent out onto another network segment. The added header may also contain other information, such as a local name for the source and destination segment (link), as well as status information that is locally useful, but not part of the packet protocol and not necessary for transmission with the packet throughout the network.

Abstract: A backplane wiring scheme is provided for use in a hub of a packet data communications system. Line cards are connected to the backplane wiring arrangement in the hub, where each line card is a coupling to a network segment, a station or a to a bridge to other stations or segments. The connection is usually in either a ring or a bus topology, and increased flexibility, reduced power consumption, and easier implementation are provided by a unique wiring scheme. Each line card has a number of receive ports (e.g., N-1) and has two transmit ports, the transmit ports including a transmit-left port and a transmit-right port. The receive ports and transmit ports are arranged in a regular linear pattern on an edge of each of said line cards.

Abstract: A system for stripping frames transmitted by a station on a token ring network is disclosed. During operation of the system, the station receives a grant of permission to transmit onto the network. In an example embodiment, the grant of permission is a token. After receipt of the grant of permission to transmit, the station transmits one or more frames onto the network. The station counts the number of frames transmitted onto the network. The count of frames transmitted onto the network is the `frame count`. Upon transmission of the frames, the station stops forwarding frames received from the network, thus removing received frames from the network. Removing received frames from the network is referred to as `stripping`. Following transmission of the information frames, the station counts the number of frames stripped from the network. The count of frames stripped from the network is the `strip count`. When the strip count equals the frame count, the station terminates stripping.

Abstract: An assembly for mounting fiber optic transceivers. A front wall having a plurality of holes is provided. A plurality of mounting members are attached to the rear of the front wall and extend perpendicularly from each of the plurality of holes. The mounting members include a base, a pair of side walls and rear wall coupled to the base, and a flexible clamp member attached to the rear wall. The flexible clamp member includes a pair of short wall portions impressed at each end to provide securing dimples and an integral back wall portion to seat the fiber optic transceiver.

Abstract: Data recovery apparatus for receiving two channels of data signal portions skewed in time and recovering from them two data signal portions synchronized with a con, non clock signal. The apparatus includes a phase comparator circuit and a latch circuit associated with each channel of data signals, a single voltage controlled oscillator that generates a clock signal VCO-CLK in response to a VCO control signal and a single charge pumping circuit for generating the VCO control signal. Each phase comparator circuit receives its associated channel of data signal portions and the VCO-CLK signal and generates pump-up/pump-down signals applied to the charge pumping circuit. Each latch circuit is triggered by a selected edge of the VCO-CLK signal, so that the latch circuits respectively provide recovered data signal portions synchronized with the VCO-CLK signal, which may then be recombined in the same sequence as they were originally divided from a common high data-rate signal.

Abstract: A technique for controlling access to a bridge connected to at least two networks, such that buffer memory requirements are minimized. For at least one target network of the two networks, two dynamic lists are maintained, to keep track of data packets received from the target network and not yet forwarded, and to keep track of data packets stored for forwarding to the target network, but not yet forwarded. The target network uses a half-duplex medium and a CSMA/CD (Carrier Sense Multiple Access with Collision Detection) protocol. The invention operates by adjusting network protocol parameters used in the target network, to either guarantee or deny priority to the target network in the event of a collision, based on the continually observed status of the two lists. One of the adjustments modifies a backoff value that determines the amount of time that the bridge device will wait, in the event of a collision, before attempting to retransmit a data packet.

Abstract: A data communication system having a plurality of nodes is disclosed. A number of transceivers is provided, each transceiver being coupled to a respective one of the plurality of nodes, for data communication between the transceiver and its associated node. Each transceiver is also provided with a controlled current source. The data communication system is also equipped with a data bus for communication of a transmitted data signal between the transceivers. A current bus which is coupled to each transceiver receives a current signal from the controlled current source when a transceiver is placing the data onto the data bus.

Abstract: A communications system having a plurality of nodes is disclosed, including a reliable method and apparatus for collision detection. Each node includes a primary and a secondary collision detection circuit, and a unique value that is included in each transmission. The unique values of the nodes are designed so that collisions not detected by the primary collision detection circuit are reliably detected by the secondary collision detection circuit, even in the presence of logic delays within the circuits, and propagation delays between nodes.

Abstract: A test fixture for facilitating connection between the test leads of a diagnostic device and a pin grid array, dispersion via, or other multi-leaded electronic components mounted on a printed circuit boards. A base is provided of a nonconductive material having holes for spring loaded test pins. In the center of the fixture is a threaded rod which attaches the fixture onto a small threaded stud attached to the printed circuit board. The screw attachment is designed so that the fixture first screws onto the metal stud with light finger pressure. A nested screw arrangement utilizing a left hand threaded part then presses the fixture against the printed circuit board, compressing the test pins for good contact.

Abstract: A station transmits a sequence of one or more frames on a token ring, keeping count of the frames transmitted. At the end of the transmitted frame the station originates onto the ring one or more coded marker frames and finally transmits a token. After the station transmission is begun, the station strips from the ring all the frames it receives, decrementing its count for each properly stripped frame, until either its count is reduced to zero or one of its marker frames is detected.

Abstract: A clip-on heat sink assembly includes a spring and electrically-insulating braces. The spring is shaped to fit over a heat sink and a chip carrier package and engage with the braces which support the chip carrier package. The spring holds the heat sink in place and forces the heat sink and the chip carrier package together in order to maintain good thermal contact. An alternative embodiment includes a spring with the braces attached to form one piece.

Abstract: A duplicate address condition in a computer network may be detected by a station of the type for attachment to a computer communications network, the network capable of maintaining communications among a plurality of stations, the station having means for receiving a frame, the frame having a source address field and a frame control field; means for maintaining an individual address of the station; means for maintaining a source address list of address, the source address list not containing the individual address; means for determining that a contents of the source address field in the frame matches at least one address in the source address list; means for determining that the frame control field of the frame has a predetermined contents; and, means, responsive to the source address of the frame matching at least one address in the source address list and the frame control field of the frame having the predetermined value, for setting an indicator that a duplicate address condition exists.

Abstract: Use of a multicast address in a LAN, where the LAN does not support an adequate multicast address space, is implemented. An apparatus is provided for delivering a multicast address to a station on a local area network, where the local area network does not support the multicast address. The frame is transmitted onto the local area network, where the frame has: a predetermined field containing a reference to the multicast address; an indicator, the indicator capable of being interpreted by a receiving station to mean that the multicast address may be recovered from the frame by parsing the frame; and an applications program may be executed in response to the multicast address. Also, the apparatus may have a receiving station capable of receiving the frame, and an applications program may be executed in the receiving station in response to the multicast address.

Abstract: An arbitration mechanism for controlling a coupling order between a number of resources and a number of requesters having a number of requests processing units, one associated with each one of the requesters, for receiving a resource type request signal from the associated requester, a number of grant processing units, one associated with each one of the resources, for monitoring a busy status signal from said associated resource, a common broadcast medium coupled to the number of request processing units and the grant processing units, and an arbiter for granting access to said common broadcast medium to one of the request processing units and the grant processing units using the common broadcast medium to control the coupling order between the requesters and the resources in a first come, first served manner.

Abstract: A communication client is connected to multiple display servers. When a client of one of the display servers issues a communication, the communication client notes the communication in the display server coupled to the client and relays the communication to the other servers for use by clients of the other servers.

Abstract: A device and related method for coupling segments of an extended local area network (LAN) in such a way that message traffic employing inter-network protocols such as TCP/IP will be handled without the difficulties usually associated with bridges, and without the complexity and expense of full IP router capability. The device operates like a bridge for non-TCP/IP traffic. For TCP/IP traffic it operates in a bridge-like manner but maintains a database associating extended LAN segment addresses with port numbers in the device, so that packets can be automatically forwarded over a spanning tree connecting the network segments. A host computer in any network segment can address others in different network segments of the extended LAN as though all were in a single LAN. The device of the invention functions to block the flow of ARP messages and to generate ARP replies that render the device of the invention transparent to hosts within the extended LAN.

Abstract: A simulation method allowing an experimenter to model a real-world situation in order to learn something about it. The method permits interaction of concurrent experiments through interaction between different variables during a single simulation run on a computer having at least one central processing unit.