Abstract: A method is provided of planning routes and allocating route identifiers in a managed frame-forwarding network. The network comprises a plurality of nodes interconnected by links, with each node being arranged to forward data frames according to a combination of an identifier and a network address carried by a received data frame and forwarding instructions stored at the node. A first step of the method identifies a sub-set of nodes which are core nodes of the network. The remaining nodes are termed outlying nodes. A spanning tree is then built off each of the identified core nodes, with the spanning tree stopping one link short of any other core node. Each spanning tree defines a loop-free path between a core node at the root of the spanning tree and a set of outlying nodes. Connections are planned between roots of the spanning trees and a different identifier is allocated to each planned connection between a pair of spanning trees.

Abstract: A node of a frame-based network has a group of outgoing links which are to be treated as an aggregated group of links. A frame distributor performs a distribution function on data frames which are intended for transmission on the group of links. The frame distributor determines if the data frame is an encapsulated data frame which forms part of a tunnelled traffic path across the network. If the data frame does form part of a tunnelled traffic path across the network, the frame distributor allocates the data frame to one of the group of links using at least part of an identifier from the header of the data frame. The identifier represents a service with which the data frame is associated, a customer or user of the data frame, or the tunnelled traffic path, which have greater variability than the backbone destination and source addresses.

Abstract: An Ethernet network comprises nodes which support a plurality of different forwarding modes. A range of VLAN Identifiers (VIDs) are allocated to each of the forwarding modes. Connections are configured between a source node and a destination node of the network using different forwarding modes. Packets carrying data traffic are sent to the destination node by selectively setting a VID in a packet to a first value, to transfer a packet via a first connection and a first forwarding mode, and a second value to transfer a packet via the second connection and the second forwarding mode. Packets received from both of the connections and sent on to an end-user. VLAN Identifiers can be allocated to different releases of functionality at nodes (e.g. software releases) such that packets are forwarded via a set of nodes supporting a first release, or via a set of nodes supporting a second release. It is possible to provide a controlled and disruption-free network evolution.

Abstract: A shared (proxy) OAM session is performed in a packet-based network on behalf of a plurality of connections. First and second connections are each routed between respective nodes of the network for carrying data traffic. The second connection shares a portion of the routing of the first connection. The shared OAM session is performed along a path which is co-routed with at least part of the shared portion of the routing of the first connection and the second connection. Failure notification signalling is propagated to an endpoint node of each of the first and second connections when the shared OAM session indicates a failure has occurred. The use of a shared OAM session reduces processing at nodes and reduces OAM traffic. Each connection can be a trunk, such as a PBT/PBB-TE trunk, or a service carried within a trunk.

Abstract: The invention relates to enabling differential forwarding in address-based carrier networks such as Ethernet networks. There is described a method of and connection controller for establishing connections (76, 77) in a frame-based communications network comprising nodes (71-75 and 78) such as Ethernet switches. The connections are established by configuring, in various of the nodes, mappings for forwarding data frames, such as Ethernet frames. The mappings are from a combination of a) a destination (or source) address corresponding to a destination (or source) node (73) of the connection and b) an identifier, such as a VLAN tag. The mappings are to selected output ports of the various nodes. By using the combination of destination (or source) address AND identifier, the mappings enable data frames belonging to different connections (76, 77) to be forwarded differentially (ie forwarded on different output ports) at a node (75) despite the different connections having the same destination node.

Abstract: The invention relates to enabling differential forwarding in address-based carrier networks such as Ethernet networks. There is described a method of and connection controller for establishing connections (76, 77) in a frame-based communications network comprising nodes (71-75 and 78) such as Ethernet switches. The connections are established by configuring, in various of the nodes, mappings for forwarding data frames, such as Ethernet frames. The mappings are from a combination of a) a destination (or source) address corresponding to a destination (or source) node (73) of the connection and b) an identifier, such as a VLAN tag. The mappings are to selected output ports of the various nodes. By using the combination of destination (or source) address AND identifier, the mappings enable data frames belonging to different connections (76, 77) to be forwarded differentially (ie forwarded on different output ports) at a node (75) despite the different connections having the same destination node.

Abstract: A system for monitoring a communications network generates a total value figure, using a store of value information. The system can identify which of the monitored flows of traffic rely on a given one or more of the components of the network, and generate a total value of all the identified flows. This type of value information can be easier for network operators to interpret because the information is more direct, and more explicit. Also, many specific rules/warnings about reconfigurations need not be provided. Values can be sent to remote field workers, or used for network configuration, network planning, and financial reporting.

Abstract: A programmable optical add/drop multiplexer (OADM) implements add/drop function of optical signals from a number of cross-connected optical systems while treating issues of coherent cross-talk, chromatic dispersion, slope of dispersion and amplitude equalization. Input WDM (wavelength division multiplexed) optical signals from a number of optical systems are each de-multiplexed into a number of optical path signal that are routed through switches and then multiplexed into a number of output WDM optical signals. Problems with coherent cross-talk in optical path signals are eliminated by introducing equivalent optical path lengths between paths through which the optical path signals propagate and by introducing dead-bands between consecutive optical path signals.

Abstract: A method is provided of planning routes and allocating route identifiers in a managed frame-forwarding network. The network comprises a plurality of nodes interconnected by links, with each node being arranged to forward data frames according to a combination of an identifier and a network address carried by a received data frame and forwarding instructions stored at the node. A first step of the method identifies a sub-set of nodes which are core nodes of the network. The remaining nodes are termed outlying nodes. A spanning tree is then built off each of the identified core nodes, with the spanning tree stopping one link short of any other core node. Each spanning tree defines a loop-free path between a core node at the root of the spanning tree and a set of outlying nodes. Connections are planned between roots of the spanning trees and a different identifier is allocated to each planned connection between a pair of spanning trees.

Abstract: A node of a frame-based network has a group of outgoing links which are to be treated as an aggregated group of links. A frame distributor performs a distribution function on data frames which are intended for transmission on the group of links. The frame distributor determines if the data frame is an encapsulated data frame which forms part of a tunnelled traffic path across the network. If the data frame does form part of a tunnelled traffic path across the network, the frame distributor allocates the data frame to one of the group of links using at least part of an identifier from the header of the data frame. The identifier represents a service with which the data frame is associated, a customer or user of the data frame, or the tunnelled traffic path, which have greater variability than the backbone destination and source addresses.

Abstract: An Ethernet virtual switched sub-network (VSS) is implemented as a virtual hub and spoke architecture overlaid on hub and spoke connectivity built of a combination of Provider Backbone Transport (spokes) and a provider backbone bridged sub-network (hub). Multiple VSS instances are multiplexed over top of the PBT/PBB infrastructure. A loop free resilient Ethernet carrier network is provided by interconnecting Provider Edge nodes through access sub-networks to Provider Tandems to form Provider Backbone Transports spokes with a distributed switch architecture of the Provider Backbone Bridged hub sub-network. Provider Backbone transport protection groups may be formed from the Provider Edge to diversely homed Provider Tandems by defining working and protection trunks through the access sub-network.

Abstract: The invention relates to enabling traffic engineering in frame-based networks such as Ethernet networks. There is described a method of and connection controller for establishing connections (76, 77) in a frame-based communications network comprising nodes (71-75 and 78) such as Ethernet switches. The connections are established by configuring, in various of the nodes, mappings for forwarding data frames, such as Ethernet frames. The mappings are from a combination of a) a destination address corresponding to a destination node (73) of the connection and b) an identifier, such as a VLAN tag. The mappings are to selected output ports of the various nodes. By using the combination of destination address AND identifier, the mappings enable data frames belonging to different connections (76, 77) to be forwarded differentially (ie forwarded on different output ports) at a node (75) despite the different connections having the same destination node.

Abstract: A system for monitoring a communications network generates a total value figure, using a store of value information. The system can identify which of the monitored flows of traffic rely on a given one or more of the components of the network, and generate a total value of all the identified flows. This type of value information can be easier for network operators to interpret because the information is more direct, and more explicit. Also, many specific rules/warnings about reconfigurations need not be provided. Values can be sent to remote field workers, or used for network configuration, network planning, and financial reporting.

Abstract: A method and apparatus for determining control signals of a filter for optimization of the gain profile of an amplifier, particularly though not exclusively for use in optical communications systems, and a system incorporating the same. The method is for calculating at least one control signal for at least one periodic filter arranged to alter the output gain profile of an amplifier, in which at least one of the phase and amplitude of the filter response are tuneable.