Abstract: A method for communication is used in a communication network that includes multiple ring nodes arranged in at least first and second ring networks, which are connected by one or more of the ring nodes serving as interconnect nodes. A data packet is accepted from a source user node served by the first ring network, for forwarding to a destination user node served by the second ring network. An identifier, which identifies an interconnect node in the first ring network through which the data packet is to be forwarded to the second ring network, is attached to the data packet in the first ring network. The data packet is forwarded over the first ring network, accepted at the interconnect node and, responsively to the identifier, forwarded from the interconnect node to the second ring network. The data packet is forwarded over the second ring network to the destination user node.

Abstract: A network element includes a backplane, which includes a backplane memory holding first medium access control (MAC) address values. The network element further includes multiple tributary modules coupled to the backplane, which include network interfaces that are configured to communicate over network trunks using MAC addresses that are respectively assigned to the network interfaces. The network element further includes a common function module (CFM), which communicates with the tributary modules and the backplane memory via the backplane, and which includes a CFM memory holding second MAC address values. The CFM is arranged to assign the MAC addresses to the network interfaces by selecting the MAC addresses from among the first MAC address values when the CFM is able to access the backplane memory, and by selecting the MAC addresses from among the second MAC address values when the CFM is unable to access the backplane memory.

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 communication includes coupling a group of switches in a Layer-2 bridged network. The interfaces of the switches are configured so that at least one interface of at least one of the switches is configured as a first interface type, and a plurality of other interfaces are configured as a second interface type. Upon receiving frames through the interfaces of the first and second types for transmission over the network, the received frames are labeled with corresponding first and second type indications. The frames are forwarded through the Layer-2 bridged network using the switches responsively to the type indications. Frames labeled with the second type indication are permitted to be transmitted through the interfaces of the first type and prevented from being transmitted through the interfaces of the second type.

Abstract: A method for assigning bandwidth in a network including nodes coupled by links arranged in a physical topology, the method including: defining between the nodes logical connections associated with a data transmission service to be provided over the network, the logical connections having a connection topology different from the physical topology, and determining respective bandwidth requirements for the logical connections based on parameters of the service. The method further includes mapping the connection topology to the physical topology, so that each of the logical connections is associated with one or more links of the physical topology, and allocating a bandwidth for the service on each of the links in response to the bandwidth requirements of the logical connections and to the mapping.

Abstract: A maintenance entity for an Ethernet Connectivity Fault Management (CFM) domain. The maintenance entity comprises a port definer module and a connection which is connected to a group of aggregated link. The port definer module examines a designated link of the group by forwarding CFM messages via the designated link.

Abstract: A method for communication includes configuring a network node having at least first and second line cards, the line cards having respective ports, to operate as a distributed media access control (MAC) bridge in a Layer 2 network. Each of the line cards has a respective forwarding database (FDB). Upon receiving a data packet on a port of the network node from a MAC source address, the data packet is conveyed to at least the first line card for transmission to the MAC destination address. The MAC source address of the data packet is checked against the records in the FDB of the first line card. If the FDB does not contain a record of an association of the MAC source address with the port on which the data packet was received, the record is added to the FDB of the first line card, which sends a message to at least the second line card informing the second line card of the association.

Abstract: A method for communication includes representing a layer 2 ring network, which includes two or more ring nodes interconnected by two unidirectional ringlets, as a plurality of unidirectional point-to-point links connecting respective pairs of the ring nodes and having respective traffic engineering (TE) related attributes. The TE-related attributes of the point-to-point links are distributed to routers of a communication network that includes the ring network. The distributed TE-related attributes are processed to determine an optimal routing path traversing the ring network from a source node to a destination node in the communication network.

Abstract: A method for communication includes receiving over a synchronous optical network link a flow of encapsulated Ethernet data frames. Two or more of the Ethernet data frames are concatenated to form an extended frame having a single start frame delimiter (SFD) and a single end frame delimiter (EFD) in compliance with an Ethernet standard, and the extended frame is transmitted over an Ethernet link.

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: 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 communication includes coupling a network node to one or more interface modules using a first group of first physical links arranged in parallel. Each of the one or more interface modules is coupled to a communication network using a second group of second physical links arranged in parallel. A data frame having frame attributes sent between the communication network and the network node is received. A first physical link out of the first group and a second physical link out of the second group are selected in a single computation based on at least one of the frame attributes. The data frame is sent over the selected first and second physical links.

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 communication includes configuring a plurality of ring nodes to communicate over a communication network that includes two or more overlapping communication rings, each ring including two unidirectional ringlets in mutually-opposite directions. A data packet including one or more header fields is accepted at an ingress ring node. An egress ring node to which the data packet is to be forwarded by the ingress ring node is determined. A subset of the rings including one or more common rings that are connected to both the ingress and egress ring nodes is identified. A ringlet of a ring among the one or more common rings is selected responsively to a respective value of at least one of the header fields of the packet. The data packet is forwarded from the ingress ring node to the egress ring node over the selected ringlet.

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: A method for establishing a connection through a communication network that includes multiple segments includes providing a sharing definition defining a sharing of bandwidth among connections in the network. Two or more candidate routes for a new connection to be established through the network are identified. For each of the two or more candidate routes, a cumulative additional bandwidth reservation to be allocated to the new connection in the segments along the candidate route is calculated responsively to the sharing definition. A preferred route having a minimum value of the cumulative additional bandwidth reservation is selected out of the two or more candidate routes. The new connection is established using the preferred route.

Abstract: A method for communication over a bi-directional ring network includes provisioning a virtual private local area network service (VPLS) over the bi-directional ring network. The VPLS includes connection termination points provisioned respectively on a plurality of the nodes so as to connect each of the plurality of the nodes to a second network external to the ring network. As long as the nodes and spans are fully operational, one or more of the connection termination points are maintained in a deactivated state, so that no more than one of the connection termination points to the second network is active. The nodes exchange messages indicative of a failure associated with the bi-directional ring network, causing at least one of the deactivated connection termination points to be activated so as to maintain connectivity among the users of the VPLS without creating a loop in the VPLS via the second network.

Abstract: A method for communication includes defining a resource-sharing group including two or more communication paths that traverse at least two different routes through a communication network, the routes traversing at least one common network element. A notification of an affiliation of the two or more communication paths with the resource-sharing group is distributed over the network. A resource associated with the at least one common network element is allocated so as to share an allocation of the resource among the communication paths in the resource-sharing group responsively to the notification.

Abstract: A method for transporting fibre channel (FC) traffic over a packet-switched communication network includes identifying a sub-sequence of repetitive FC signals in a first sequence of FC words accepted over a FC link from a source FC device. The first sequence of FC words is translated into a second sequence of data packets in accordance with a communication protocol supported by the packet-switched communication network. The second sequence includes a repetition indication packet that identifies the sub-sequence of repetitive FC signals. The second sequence of the data packets is transported to a receiver over the packet-switched communication network using the communication protocol.

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.