Digital Equipment Corporation

Cabletron Systems, Inc.

Enterasys Networks, Inc.

Intel Corporation

Robert J Simcoe

Robert E Thomas

George Varghese

Anna Charny

Barry A Spinney

Gregory M Waters

Peter J Roman

Naimish Patel

Peter L Higginson

Pattabhiraman Krishna

John Bassett

Graham Cobb

Koichi Tanaka

Bruce A Schofield

Jerry D Hutchison

Wing Cheung

Cuneyt M Ozveren

Robert J Hannemann

Richard L Kirk

Hallam G Murray, Jr

Raymond G Stephany

Jeffrey L Cooper

Stanley J Czerepak

Dave Kellerman

A congestion management technique achieves an end-to-end data flow rate that is supported by a lossless communications network. The end-to-end rate extends from a source end node to destination end node of the network and is preferably at or slightly below a bottleneck rate of the network. The destination end node determines, on its own and without any help from network elements, a supportable rate of activity in the network and provides feedback to the source end node. By achieving such a rate, data transmitted by the source end node can flow through the network without loss of packets and without the use of substantial buffering.

Technique for providing end-to-end congestion control with no feedback from a lossless network

A switching method and apparatus operates as a work conserving network device. An arbiter using an arbitration algorithm controls a switch fabric interconnecting input ports and output ports. To switch cells, a virtual output queue of an input port is selected that corresponds to an output port with a lowest occupancy rating and a request is sent to this output port. In a greedy version of the algorithm, input ports may send requests to the lowest occupied output port for which they have a cell. In a non-greedy version, requests may only be sent if that input port has a cell for the lowest occupied output port in the entire network device. An output port that receives one or more requests from input ports uses an input port selection algorithm to select an input port from which to receive a packet. After as many input and output ports are matched as is possible in a phase, the packets for those matched ports are transferred across the switch. The switch fabric operates with a speedup of only twice that of the input port data rates and is still work conserving.

Method and apparatus for providing work-conserving properties in a non-blocking switch with limited speedup independent of switch size

A network device for interconnecting computer networks, the device including a bridge having a plurality of ports through which network communications pass to and from the bridge, the bridge also including a first interface enabling a user to partition the plurality of bridge ports into a plurality of groups, wherein each group represents a different virtual network, wherein the bridge treats all ports within a given group as part of the virtual network corresponding to that group and the bridge isolates the virtual networks from each other, whereby any communications received at a first port of the bridge are directly sent by the bridge to another bridge port only if the other bridge port and the first bridge port are part of the same group.

Virtual LANs

A method for improving modal bandwidth in computer networks using multimode optical fiber and laser sources is disclosed in which an annular beam is generate by the laser source, thus preventing center fiber transmission modes from reaching the detector. This prevents or lessens a pulse-splitting effect at the detector. The annular beam is generated preferably by configuring a vertical cavity surface emitting laser to have a center totally-reflecting block of 5-7 microns to generate a substantially dark-centered beam.

Method and system for preventing low order optical transmission modes in multimode optical fiber computer network using annulus laser

An arbitration scheme for providing deterministic bandwidth and delay guarantees in an input-buffered crossbar switch with speedup S is presented. Within the framework of a crossbar architecture having a plurality of input channels and output channels, the arbitration scheme determines the sequence of fixed-size packet (or cell) transmissions between the inputs channels and outputs channels satisfying the constraint that only one cell can leave an input channel and enter an output channel per phase in such a way that the arbitration delay is bounded for each cell awaiting transmission at the input channel. If the fixed-sized packets result from fragmentation of variable size packets, the scheduling and arbitration scheme determines deterministic delay guarantees to the initial variable size packets (re-assembled at the output channel) as well.

Method for providing bandwidth and delay guarantees in a crossbar switch

A content addressable memory (CAM) structure, and a method for its use, wherein data items of different selected lengths stored in the CAM may be located by matching sequences of CAM data words with sequences of input data words. Extension bits associated with each CAM data word control a sequence of comparison cycles to permit an input data item to be compared simultaneously with multiple input data items of the same length stored in the CAM structure. The CAM structure can be used without modification to store data items of various selected lengths. A begin bit associated with each CAM data word is used to mark the beginning of each stored data item and, in an exact match mode of operation, a global line is used to mark the beginning of an input data item. Match logic associated with each CAM data word generates a match till now signal in each comparison cycle, and the signal is propagated to the end of the data item if an exact match is detected. The exact match and match till now signals are used to generate various global match indications in the CAM structure. The same CAM structure can also be operated in a sliding match mode in which each stored data item is compared with every possible sequence of input data words.

Method and apparatus for matching data items of variable length in a

A method of scheduling the transmission of cells from a network node involves storing entries in a schedule table at predetermined locations, wherein each location represents a point in time at which a cell is to be transmitted. Each entry in the table contains a pointer to a list of virtual circuits having cells scheduled for transmission at the time corresponding to the location of the entry in the table. When a VC has a cell to be transmitted at a particular time, the VC is queued to the head, rather than the tail, of the list of VCs pointed to by the pointer located at the entry in the table corresponding to the time at which the cell is to be transmitted. The VC is therefore the first VC transmitted from the list of VCs.

Apparatus and method for scheduling virtual circuit data for DMA from a

A network device for interconnecting computer networks, the device including a bridge having a plurality of ports through which network communications pass to and from the bridge, the bridge also including a first interface enabling a user to partition the plurality of bridge ports into a plurality of groups, wherein each group represents a different virtual network, wherein the bridge treats all ports within a given group as part of the virtual network corresponding to that group and the bridge isolates said virtual networks from each other, whereby any communications received at a first port of the bridge are directly sent by the bridge to another bridge port only if the other bridge port and the first bridge port are part of the same group.

Device for partitioning ports of a bridge into groups of different

A method and apparatus for transferring data units between a host memory and a peripheral interface, the data units being subject to a flow control mechanism whereby some of said data units are flow controlled and some of said data units are not. Two transmit buffer memories are coupled to the peripheral interface; one for storing controlled data units to be transferred to the peripheral interface and the other for storing uncontrolled data units to be transferred to the peripheral interface. A single request buffer stores successive requests for data to be transferred from a host memory to either of the two transmit buffer memories. Data transfer circuitry transfers data from the host memory to either of the two transmit buffer memories in response to the requests stored in the request buffer. The data transfer circuitry is prevented from transferring further data from the host memory to the transmit buffer memory storing the controlled data units when it is determined that there is not enough room in the transmit buffer memory storing the controlled data units to accommodate another data unit. The data transfer circuitry is allowed, however, to transfer further data from the host memory to the transmit buffer memory storing the uncontrolled data units.

Transmit data FIFO for flow controlled data

A mechanism for operating a configurable switch to dynamically (i) route each of the data packets in an ordered string from a particular switch input port through a selected member output port of a hunt group; and (ii) route data packets which need not be transmitted in order from the input ports to available member output ports of the hunt group, as the members become available. A controller assigns each input port a service number, and directs member output ports to handle requests for ordered data packet transmissions from input ports with particular service numbers, such that the ordered transfers from an input port are handled by a single member of each group. The input port broadcasts, through the switch, a request to send ordered data packets through a particular hunt group and includes its service number in the request. The group member assigned to handle ordered transfers from the input port responds by identifying itself. Thereafter, the input port sends its ordered data packets to the identified member. Unordered data packets are queued and routed dynamically through the members of the group, as the members become available. In a local area network, data is sent from a source station to file servers using server group identifiers for multiple-route transfers or individual server identifiers for single-route transfers.

Method and apparatus for dynamically controlling data routes through a

A flow control system is disclosed, for a transmitting node and a receiving node. The transmitting node and the receiving node are linked together through multiple connections or virtual circuits. A flow control circuit in the transmitting node limits the number of data transmission units transmitted from the transmitting station, and not yet copied out of the receive buffers in the receiving node, to the total number of receive buffers in the receiving node. The flow control circuit in the transmitting node further controls the transmission of data transmission units on the multiple connections fairly, such that all connections are provided a proportional amount of the total available receive buffers in the receiving node. In an example embodiment, a global counter is used to maintain the total number of receive buffers containing data in the receiving node, and a global limit register contains the maximum number of receive buffers containing data in the receiving node allowed for a single connection. The flow control circuit further includes logic providing fair and efficient allocation of receive buffers across all virtual circuits between a transmitting node and a destination node. The flow control circuit ensures that during steady state operation, receive buffers in the receiving node, which are used to store data transmission units received from the transmitting node, are fairly divided among all active virtual circuits in the transmitting node.

Flow control with smooth limit setting for multiple virtual circuits

A computer system having an arbitration mechanism for controlling the coupling order between a plurality of requesters and a plurality of resources, where each resource has an associated resource type. The arbitration mechanism includes a plurality of request processing units, each associated with one of the plurality of requesters. The request processing units receive resource type request signals from an associated requester. The arbitration mechanism also includes a plurality of grant processing units, each associated with one of the plurality of resources. The grant processing units monitor a status signal from its associated resource. The arbitration mechanism further includes a common broadcast medium which is coupled to all of the request processing units and grant processing units. The request and grant processing units arbitrate for access to the common broadcast medium, and then use the common broadcast medium to exchange information to control the coupling order between the plurality of resources and the plurality of requesters in the computer system. When a request processing unit and a grant processing unit have arbitrated for the coupling of a particular requester and a particular resource, a controller establishes a connection between the requester and the resource through a resource access path.

Fast arbiter having easy scaling for large numbers of requesters, large

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. Local congestion information, results of address translations, and end-of-message information, are examples of such status information.

Packet format in hub for packet data communications system

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.

A plug-in logic board for use in an arbitration mechanism is disclosed. The disclosed arbitration mechanism includes two or more request processing units, two or more grant processing units and a common broadcast medium. The request processing units and the grant processing units use the common broadcast medium to control the coupling between requesters and resources on a first come, first served basis. The disclosed logic board includes a request processing unit coupled to the common broadcast medium, a grant processing unit coupled to the common broadcast medium, and an input/output unit coupled to an electronic operating device. The input/output unit passes a resource type request signal from the electronic operating device to the request processing unit, and passes a status signal received from the electronic operating device to the grant processing unit. The input/output unit further outputs a grant signal received from the request processing unit to the electronic operating device. The disclosed logic board further includes a means, responsive to said resource type request signal, said status signal, and said grant signal, for coupling a requester type electronic operating device to a resource type electronic operating device using a resource access path.

Growing community of inventors

Westborough, MA, United States of America

Robert J Simcoe