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 fault protection in a bidirectional ring network includes transmitting first and second flows of packets around the bidirectional ring network while defining the first flow as a wrapping flow and the second flow as a non-wrapping flow. Upon detection by a node in the network that a segment of the network proximal to the node has failed, the packets in the first flow are wrapped at the node between clockwise and counterclockwise directions on the network so as to avoid the failed segment, while the packets in the second flow are not wrapped.

Abstract: A method and apparatus for transmitting data over a channel having a variable transmission rate. A transmitter determines the rate of transmission of the data over the channel and receives a datagram for transmission over the channel at the determined rate of transmission. The transmitter divides the datagram into fragments of a size no greater than a size limit that is set for the datagram responsive to the determined rate of transmission and transmits the fragments over the channel.

Abstract: A method for transmitting data over a channel includes receiving a first datagram for transmission at a first priority, and receiving a second datagram for transmission at a second priority, higher than the first priority, before the transmission of the first datagram is completed. The first datagram is divided into a plurality of fragments, including a first fragment and a last fragment. The fragments of the first datagram are transmitted over the channel, beginning with the first fragment. At least a fragment of the second datagram is transmitted over the channel before transmitting the last fragment of the first datagram.

Abstract: A method for data communications includes linking a plurality of edge devices to communicate with a remote network device via a network in accordance with a packet-oriented Layer 2 communication protocol. At each of the plurality of edge devices, incoming data frames are received from client nodes in accordance with respective native Layer 2 protocols, at least one of which is different from the packet-oriented Layer 2 communication protocol. The received incoming data frames are converted at each of the edge devices from at least a first format specified by the native Layer 2 protocols to a second format specified by the packet-oriented Layer 2 communication protocol. The incoming data frames are transmitted in the second format via the network to the hub.

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 performance management unit manages a primary interface and a standby or secondary interface to two channels of an optical communications network having APS capabilities. Each performance parameter is associated with three counters. First and second counters are linked to registers of the primary and the secondary ports, and the third counter is linked to the registers of the currently active port. When a protection switch occurs, the first and second counters are immediately read and reset. The third counter continues accumulating data, but becomes associated with the new active port. At the end of a read interval, the third counter correctly reflects the number of data received, regardless of switchovers between the primary and secondary channels.

Abstract: A method for data communications includes receiving a time-division-multiplexed (TDM) input signal carrying a payload comprising data and determining whether the data comprise synchronous or non-synchronous data. A first encapsulation scheme is selected if the data comprise synchronous data, and a second encapsulation scheme is selected if the data comprise non-synchronous data. The data are encapsulated for transmission over a packet-switched network in accordance with the selected encapsulation scheme.

Abstract: A method for changing a network characteristic or capability, such as the communication rate of network segments, software version or protocol. All nodes in the network perform the change synchronously while continuing to communicate within the existing capabilities. A new configuration is downloaded to the nodes, and a manager node exchanges validation messages with the other nodes in order to verify that the nodes can be reconfigured and will be able to complete the process successfully. The manager node then sends a command message to the other nodes to execute the change. In response, the other nodes begin substantially simultaneously to communicate in accordance with the new characteristics and/or capabilities. This method helps to minimize the duration of the upgrade process, while avoiding traffic hits and minimizing abnormal operation that may occur during the upgrade.

Abstract: A data communication network includes a plurality of primary virtual bridges, interconnected by primary virtual connections so as to transmit and receive data packets over the network to and from edge devices connected thereto. One or more backup virtual bridges, each associated with at least one of the primary virtual bridges, are connected by at least one secondary virtual connection to at least another one of the primary virtual bridges, so that upon a failure of one of the primary virtual bridges with which it is associated, the backup virtual bridge transmits and receives the data packets over the network via the at least one secondary virtual connection in place of the at least one of the primary virtual bridges.

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: Explicit routing of network traffic over RPR rings using MPLS signaling techniques, including unnumbered links. A modified LSP_TUNNEL_INTERFACE_ID object is provided with a RPR IP address instead of the conventional LSR Router ID, and with a direction indicator in place of the conventional interface ID. A novel subobject is included in the ERO and RRO, which holds the RPR IP address of the sending node in place of the conventional router ID, and a direction indicator in place of the conventional interface ID. The network nodes inspect the directional indicator that is received in a path message or a Resv message to determine the direction in which traffic is to be sent and received in an explicit route.

Abstract: A method for self-testing of an electronic system that includes a main module and subsidiary modules, which are connected to the main module by data lines, at least some of which may be idle. One of the idle lines is selected to serve as an aid line, and the subsidiary module to which the aid line is connected is instructed to loop back traffic reaching the subsidiary module via the aid line. Another idle line is selected for testing, and a switch in the main module is configured to link the aid line and the line under test. The subsidiary module to which the line under test is connected transmits test traffic over the idle line to the main module. If the test traffic does not return to the subsidiary module within a predetermined period of time, a failure is reported.

Abstract: A performance monitoring system for a digital network is installed in network elements having performance monitoring responsibilities. Apparatus is provided for network elements, in which a bitmap representation of performance primitives detected during an acquisition interval is used as a control in the tracking and updating of network performance parameters. Immediate access to states that enable and inhibit the evaluation of individual performance parameters is available.

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 traffic engineering in a communication system made up of network nodes arranged in multiple interconnected networks, including at least one bi-directional ring network having an inner ring and an outer ring. The bi-directional ring network is defined as a multi-access network for purposes of a routing protocol used in the system. Constraint information is advertised with regard to connections on the inner and outer rings between the nodes within the at least one bi-directional ring network. Traffic flow is routed through the system in accordance with the routing protocol, so that the flow passes through the at least one bi-directional ring network on at least one of the connections on one of the inner and outer rings that is selected responsive to the constraint information.

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 controlling a system of label-switched tunnels through a communication network, the method including pushing a signaling label onto a signaling frame at a first node in the network, and sending the signaling frame through the label-switched tunnels to one or more recipient nodes in the network. The signaling label is popped off the signaling frame at the one or more recipient nodes, which responsive to the signaling label, process the signaling frame so as to eliminate loops formed by the label-switched tunnels.

Abstract: A method for eliminating loops in a communication network in which the nodes operate as virtual bridges, having virtual ports that link the virtual bridges over virtual connections, each of the virtual connections coinciding respectively with one or more segments of the network. Respective port costs are assigned to the virtual ports responsive to a count of the network segments with which the respective virtual connections coincide, so as to favor virtual paths between pairs of the nodes that are made up of a greater number of the virtual connections, relative to the virtual paths that are made up of a lesser number of the virtual connections. Respective path costs are computed for the virtual paths, based on the port costs, and the virtual connections over which to send traffic between the virtual bridges are selected responsive to the path costs.

Abstract: A method for data communications includes receiving a time-division-multiplexed (TDM) input signal on a first circuit, the signal including an input sequence of frames of data, each such frame divided into sections for carrying respective sub-rate payloads. After determining which of the sections are active, such that the data in the sub-rate payloads of the active sections include user data, and which of the sections are inactive, the user data in the active sections are encapsulated into data packets for transmission over a packet network, while omitting from the packets at least some of the data from the inactive sections.