Abstract: A method for data broadcast over a network includes receiving at a virtual bridge a data packet to be flooded over the network, and passing the data packet from the virtual bridge to a multicast-capable router, along with a broadcast indication. Responsive to the broadcast indication, the router determines a group of destination addresses to which the packet should be multicast, and creates copies of the packet for transmission over the network to the destination addresses in the group.

Abstract: A method for establishing a connection with a guaranteed bandwidth for transmitting data over a logical link that includes a plurality of parallel physical links between first and second endpoints. A link bandwidth is allocated on each of the physical communication links so as to include a predefined safety margin, based on either a failure protection policy, or a measure of fluctuation that occurs in a rate of data transmission over the physical links, or both. A sum of the allocated link bandwidth over the plurality of the parallel physical links is substantially greater than the guaranteed bandwidth of the connection. The data are conveyed over the logical link by distributing the data for transmission among the physical links in accordance with the allocated link bandwidth.

Abstract: A method for handling traffic in a communication network includes setting an aggregate limit on a total rate of transmission of information by a group of flows to be transmitted over the network, and setting a respective individual limit on an individual rate of transmission by each of the flows in the group. When the information carried by packets in any given one of the flows is in excess of the respective individual limit, the packets in excess of the respective individual limit in the given one of the flows are tagged with a first excess flow tag. When the total rate of transmission of the information is in excess of the aggregate limit, the packets in excess of the aggregate limit are tagged with a second excess flow tag. Resources in the network are allocated to convey the packets responsive to the first and second excess flow tags.

Abstract: A communication device for interconnection of first and second networks, of which at least the first network is a bidirectional ring network, includes first and second interconnect modules, each such module adapted to receive outgoing data traffic on the first network at a data rate not substantially greater than a predetermined maximum rate for one of the ring directions, and to convey the outgoing data traffic to the second network. When a fault occurs in one of the first and second modules, the other module is reconfigured to receive substantially all of the outgoing data traffic and to convey the outgoing data traffic to the second network regardless of whether the outgoing data traffic is transmitted on the first network in the clockwise or in the counterclockwise direction.

Abstract: A method for communication via a ring network that includes a plurality of nodes. The method includes receiving at a first node in the ring network a data packet transmitted over a virtual private LAN service (VPLS), the data packet including an identification of the VPLS. The first node reads the identification from the data packet. Responsively to reading the identification, the first node forwards the data packet to at least one second node in the ring network that is associated with the VPLS.

Abstract: Communication apparatus includes a plurality of interface cards, including a central interface card and spoke interface cards, which are adapted to link communication lines to a network. A protection bus includes multiple spoke connections that link the central interface card to the spoke interface cards in a partial star configuration, such that on at least one of the spoke connections there are two of the spoke interface cards connected together to the central interface card.

Abstract: A method for communication includes setting respective overbooking ratios for multiple categories of data traffic, and assigning respective bandwidth allocations to a plurality of connections for transmitting the data traffic in one or more of the categories over a network. The data traffic from the connections is coupled into respective queues, such that each of the queues is associated with one or more of the connections. Respective weights are computed for the queues responsively to the bandwidth allocations and to the overbooking ratios of the categories of the data traffic to be transmitted on the connections that are associated with each of the queues. A multiplexer multiplexes among the queues responsively to the respective weights so as to transmit the data traffic from the connections over a link in the network.

Abstract: A method for configuration of a node inserted into a bidirectional ring network includes, responsive to traffic on first and second rings of the network, determining at the node that one of the first and second rings carries the traffic in a clockwise direction around the network, while the other of the rings carries the traffic in a counterclockwise direction. The node then sends and receives advertisement packets through its network interfaces over the respective rings, advertising the determined directions of the traffic carried by the rings. Responsive to the advertisement packets received at the node, the configuration of the node is completed so that the traffic can be sent to and from the node on the first and second rings in the determined directions.

Abstract: A method for routing a data flow from a source node to a destination node among a plurality of nodes mutually linked in a ring by segments of a communication network, configured so that the data flow can traverse the ring in either of first and second, mutually-opposing directions of communication. The method includes maintaining at each of the nodes a record of respective levels of use of a network resource on the segments in the ring for both the first and second directions of communication. Responsive to the respective levels of use, one of the directions is selected at the source node, in which to route the data flow to the destination node. A notification is sent from the source node to the other nodes in the ring of an additional allocation of the resource required by the source node in order to convey the data flow to the destination node in the selected direction on the segments in the ring.

Abstract: A communication network includes a communication medium and a plurality of communication nodes, mutually coupled by the communication medium so as to form a ring, over which each of the nodes is configured to transmit traffic to the other nodes in both clockwise and counterclockwise directions around the ring. At least one of the nodes is configured to receive the traffic in only one of the directions at any given time.

Abstract: A method for fast protection in a fault-tolerant network includes coupling an edge switch in a network to one or more access switches via at least first and second redundant links, respectively connected to first and second ports of the edge switch. The first port is placed in an active state, while the second port is placed in a blocking state, so that communication traffic is conveyed over the first link, and each of the switches builds a respective database for use in forwarding the traffic. Responsive to a failure associated with the first link, the second port is placed in the active state and the first port is placed in the blocking state. Dummy traffic is then sent from the edge switch over the second link to the one or more access switches, so as to cause each of the one or more access switches to modify its respective database responsive to the second port being in the active state.

Abstract: A method for establishing a connection with a guaranteed bandwidth for transmitting data over a logical link that includes a plurality of parallel physical links between first and second endpoints. A link bandwidth is allocated on each of the physical communication links so as to include a predefined safety margin, based on either a failure protection policy, or a measure of fluctuation that occurs in a rate of data transmission over the physical links, or both. A sum of the allocated link bandwidth over the plurality of the parallel physical links is substantially greater than the guaranteed bandwidth of the connection. The data are conveyed over the logical link by distributing the data for transmission among the physical links in accordance with the allocated link bandwidth.

Abstract: Communication apparatus includes a plurality of interface cards, including a central interface card and spoke interface cards, which are adapted to link communication lines to a network. A protection bus includes multiple spoke connections that link the central interface card to the spoke interface cards in a partial star configuration, such that on at least one of the spoke connections there are two of the spoke interface cards connected together to the central interface card.

Abstract: A method for data broadcast over a network includes receiving at a virtual bridge a data packet to be flooded over the network, and passing the data packet from the virtual bridge to a multicast-capable router, along with a broadcast indication. Responsive to the broadcast indication, the router determines a group of destination addresses to which the packet should be multicast, and creates copies of the packet for transmission over the network to the destination addresses in the group.

Abstract: A method for fast protection in a fault-tolerant network includes coupling an edge switch in a network to one or more access switches via at least first and second redundant links, respectively connected to first and second ports of the edge switch. The first port is placed in an active state, while the second port is placed in a blocking state, so that communication traffic is conveyed over the first link, and each of the switches builds a respective database for use in forwarding the traffic. Responsive to a failure associated with the first link, the second port is placed in the active state and the first port is placed in the blocking state. Dummy traffic is then sent from the edge switch over the second link to the one or more access switches, so as to cause each of the one or more access switches to modify its respective database responsive to the second port being in the active state.

Abstract: A method for handling traffic in a communication network includes setting an aggregate limit on a total rate of transmission of information by a group of flows to be transmitted over the network, and setting a respective individual limit on an individual rate of transmission by each of the flows in the group. When the information carried by packets in any given one of the flows is in excess of the respective individual limit, the packets in excess of the respective individual limit in the given one of the flows are tagged with a first excess flow tag. When the total rate of transmission of the information is in excess of the aggregate limit, the packets in excess of the aggregate limit are tagged with a second excess flow tag. Resources in the network are allocated to convey the packets responsive to the first and second excess flow tags.

Abstract: A method for configuration of a node inserted into a bidirectional ring network includes, responsive to traffic on first and second rings of the network, determining at the node that one of the first and second rings carries the traffic in a clockwise direction around the network, while the other of the rings carries the traffic in a counterclockwise direction. The node then sends and receives advertisement packets through its network interfaces over the respective rings, advertising the determined directions of the traffic carried by the rings. Responsive to the advertisement packets received at the node, the configuration of the node is completed so that the traffic can be sent to and from the node on the first and second rings in the determined directions.

Abstract: A communication device for interconnection of first and second networks, of which at least the first network is a bidirectional ring network, includes first and second interconnect modules, each such module adapted to receive outgoing data traffic on the first network at a data rate not substantially greater than a predetermined maximum rate for one of the ring directions, and to convey the outgoing data traffic to the second network. When a fault occurs in one of the first and second modules, the other module is reconfigured to receive substantially all of the outgoing data traffic and to convey the outgoing data traffic to the second network regardless of whether the outgoing data traffic is transmitted on the first network in the clockwise or in the counterclockwise direction. Typically, each module has its own MAC address, but when the fault occurs in one of the modules, the other module receives the traffic transmitted both to its own MAC address and to the MAC address of the failed module.

Abstract: A communication network includes a communication medium and a plurality of communication nodes, mutually coupled by the communication medium so as to form a ring, over which each of the nodes is configured to transmit traffic to the other nodes in both clockwise and counterclockwise directions around the ring. At least one of the nodes is configured to receive the traffic in only one of the directions at any given time.

Abstract: A method for routing a data flow from a source node to a destination node among a plurality of nodes mutually linked in a ring by segments of a communication network, configured so that the data flow can traverse the ring in either of first and second, mutually-opposing directions of communication. The method includes maintaining at each of the nodes a record of respective levels of use of a network resource on the segments in the ring for both the first and second directions of communication. Responsive to the respective levels of use, one of the directions is selected at the source node, in which to route the data flow to the destination node. A notification is sent from the source node to the other nodes in the ring of an additional allocation of the resource required by the source node in order to convey the data flow to the destination node in the selected direction on the segments in the ring.