Abstract: A rate based, end to end flow control system is disclosed for a communications network. The disclosed rate based flow control system includes each source end station selecting its transmission rate from a set of permitted discrete transmission rates. The set of permitted discrete transmission rates is based on a logarithmic encoding. The disclosed rate based traffic control system further requires each source end station to send one end to end control cell every time period T. The time period T is also known by switches in the communications network and is used to periodically calculate an available allocation (“fair share”) of bandwidth at a switch for a given virtual circuit.

Abstract: Controlling a user's usage of network resources, after the user has been authenticated, without using any network resources beyond the user's entry point to the network. A plurality of users may be connected to an entry point of a network of a network device by a shared transmission medium. Each users' usage of network resources is controlled, after such user has been authenticated, without using any network resources beyond such user's entry point to the network. For each one or more users, packet rules may be provisioned to the user's entry point to the network, where such entry point may be shared with other users. The packet rules may be applied to each packet received from the user before any network resources beyond the entry point are used. These packet rules may be associated with an identity of the user and then provisioned to the user's entry point in response to the user being authenticated.

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 (n2−n)/2 unique pairs of LANs connected by the bridge with (n2−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 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.

Abstract: 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.

Abstract: 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.

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 user of a remote typically has a choice of multiple access methods and telephone numbers using which the user can connect his remote computer to a local computer or a local area network. The remote user often user faces several problems. These problems include first knowing what numbers and access methods the user has a choice of, and knowing the cost of using those numbers and access methods. This first problem is exasperated by a large number of available access points, changes of access telephone numbers, changes in telephone and network access rates, and changes in quality of service provided by various service providers. Distributing, storing, and searching a comprehensive directory of access numbers and associated costs would, in general, be prohibitive on remote computers with limited storage and computation capacity, such as portable computers typically often used by mobile workers.

Abstract: A switch for use in a communications system having multiple local area networks interconnected by multiple switches so as to be configurable into different types of virtual local area networks includes first and second communication ports. The first communication port is connected directly to a local area network and the second communication port interconnects with other system switches. A switch control detects a communication from the local area network and identifies a virtual local area network over which the communication is to be transmitted based upon rules of precedence for different types of virtual local area networks. The communication is appended with a VLAN tag representing the identified virtual local area network so as to form a VLAN communication that is directed to the second communication port for transmission over the identified virtual local area network.

Abstract: An Electromagnetic Interference (EMI) shielding system including a conductive clip for electrically coupling a printed circuit board (PCB) to a grounding structure. The clip includes a first contact section attached to a side rather than an edge of the PCB, and a second contact section for contacting the grounding structure. The clip is compressible to ensure a tight fit of the second contact section to the grounding structure. The clip may be formed as a unitary structure and includes transition regions between the first and second contact sections that provide flexibility to the structure. Edge flaps may optionally be included to enhance surface contact of the clip to the PCB. The second contact region is preferably designed with a flat top surface to enable automated surface mounting.

Abstract: A method and apparatus are provided for using shared-media networks in a connection-based networking scheme. The method and apparatus may include filtering of packets received by a switch in the shared-media subnetwork. In-line filtering of packets is also disclosed.

Abstract: A switch for use in a virtual area network communications system having multiple local area networks interconnected by multiple switches which are connected by a trunk having one or more trunk stations connected directly thereto, includes a first communications port, i.e., an access port, which connects to a first local area network. The first local area network is configured within a virtual area network which also includes a second local area network and a trunk station. The switch also includes a second communications port, i.e. a trunk port, connected to the trunk to which the trunk station is connected by another trunk port.

Abstract: A method and system for requesting an interrupt from a host system to service an adapter connected to the host system and a data interface. Data packets, including one or more data cells, are transferred between the data interface and the host system. The host system includes a host memory that includes a plurality of memory slots to store data packets transferred between the data interface and the host system. It is determined when a transfer of data has resulted in an occurrence of an interrupt event. An interrupt event occurs when the transfer of data includes a transfer of a data cell between the data interface and the host system and the data cell is defined to be an end of a data packet. In response to the occurrence of an interrupt event, it is determined whether to generate an interrupt request to the host system.

Abstract: A switch for selectively precluding the issuance of interswitch resolve packets. When the address of a destination node is not able to be resolved by an interswitch resolve packet, the destination identifier for the packet is stored in an unresolved address table. The unresolved address table includes a destination identifier of the packet, a counter and one or more timers. When the value of the counter reaches a test count value it is determined whether or not the packets have been sent at a rate (indicated by a threshold value) that would unduly degrade the performance of the network. If the resolve packets are unduly loading the network, then the destination identifier is forwarded to a blocked address table. Subsequent issuance of interswitch resolve packets having the destination identifier are selectively filtered to ensure that they do not unduly degrade the performance of the computer network.

Abstract: An apparatus and method for allocating the performance of applications in a networking chassis among one or more modules in the chassis. In particular, the system acts as a chassis agent for performing network management functions. The agent performs a discovery function whereby each module discovers the location and current utilization of resources and applications for itself and transmits that information to other modules, and wherein each module maintains a slot table of such information for all modules. Based on the information in the slot table, each module performs an election function for allocating applications among the various modules in the chassis. The agent uses MIBs to gather information about the chassis and to effect control on the chassis, wherein each managed object is registered both locally and remotely in a MIB tree maintained on each module, and the data is maintained locally on the module on which the managed object resides.

Abstract: A method and apparatus are provided for connection-oriented switching in a communications network wherein a pre-established path is established between a select pair of an ingress switch and an egress switch. The use of pre-established paths enables a reduction in the total number of connections required inside the switch cloud, reduces the CPU load on trunk switches, and shortens the time for connection setup. In the embodiment described, the DA/SA fields of a MAC frame data packet are replaced with a “virtual path”, which identifies the pre-established path between the ingress and egress switches. A “virtual circuit” is provided in another field of the modified packet which specifies the out-port and out-header on the egress switch for demultiplexing the modified packet upon receipt at the egress switch. The virtual circuit is exchanged between the ingress and egress switches at connection setup.

Abstract: A technique for logically connecting local communications networks (CNs) that may be separated by wide area networks containing routers and other network components. A logical link is formed between two devices called tunnelers, such that, once a tunnel has been established between two CNs, other devices on the CNs can communicate. The tunneling mechanism of the invention requires that each CN have only one active tunneler at any particular time, referred to as the designated tunneler, and each of the tunnelers is configured to have knowledge of the identities of the other tunnelers. A tunnel is established after a successful exchange of messages between two tunnelers, and then traffic may be forwarded through the tunnel in a transparent manner. The tunneling mechanism permits messages to be forwarded between CNs separated by a wide area network containing routers.

Abstract: A repeater, which forwards data packets from a first Ethernet collision domain to a second Ethernet collision domain while filtering packets so as to eliminate unnecessary packets from being transmitted onto Ethernet networks, has a register for each port, where the register holds the address of a workstation from which the port last received a data packet. When a data packet addressed to that port is received by another port, the repeater asserts a signal line informing the other ports that the dat apacket may be ignored by them, and the addressed port receives the data packet for transmission onto the Ethernet collision domain connected thereto.

Abstract: Bus access is arbitrated among modules connected to a common bus. Each module has a priority level and an arbitration number assigned to it. More than one module can have the same priority level. For each priority level, the arbitration numbers assigned are unique. When two or more modules attempt bus access at the same time, the one with the higher priority level wins access. If the priority levels are the same but one module has already accessed the bus, the module that has been waiting wins access. If the modules have the same priority level and have been waiting then the module with the highest arbitration number wins access.

Abstract: A packet is originated in a unit 10 as a data field DATA 11 plus a CRC (cyclic redundancy check) check field CRC 12 by a CRC circuit 13. This packet has a header HDR (with a routing information field RIF) added to it in a unit 20, converting it into a message for transmission through a message network. A check correction field CCF is computed by unit 23 in unit 20, by looking up precomputed check subfields stored with the routing subfields (the routing information field being constructed by selecting from the stored subfields), such that the CRC field is a valid CRC check field for the complete message. At the destination, unit 30 can be the final user unit, checking the entire message and extracting the data field DATA therefrom; the DATA field does not need to be checked, as the CRC field acts as a check both for the data field DATA alone and the entire message.