Abstract: Optical communication networks often incorporate fiber rings or fiber mesh topologies for interconnecting its nodes. Both of these topologies can contain closed optical loops at one or more wavelengths within the optical spectrum. In amplified optical systems, the inherent loss of these optical loops is counteracted by the amplifier gain. Thus, the optical loop may have a net loss that is too low to prevent excessive noise buildup resulting in a lasing fiber loop. The noise that builds up within such amplified systems is dominated by the Amplified Spontaneous Emission (ASE) noise resulting in ASE loops. Such loops can have a serious impact on all wavelengths carried by the fiber and lead to a partial or complete loss of end to end communication due to a severe degradation in signal to noise ratio. This invention provides an effective method and system for avoiding ASE loops in optical communication networks.

Abstract: This invention provides a method for commissioning and upgrading an optical ring network using its internal amplifiers as Automatic Spontaneous Emission sources of light that are used in making measurements. A modular segmented approach is adopted and the network is commissioned segment by segment. A flexible method is used for upgrading a commissioned network by adding or deleting a node or changing the internal configuration of a node. The method uses techniques for the correction of the Optical Signal to Noise Ratio induced error as well as the Spectral Filtering Error during the loss computation required for adjusting the gains of the amplifiers at each network node to an appropriate value. Since the method does not require an external laser source that needs to be moved manually from node to node it greatly reduces the commissioning time. Since it uses only the components of the network itself and does not deploy any additional device it also leads to a significant saving in cost.

Abstract: A routing system and method are provided which use a composite cost in identifying routes. This allows a simple way of identifying the best route taking multiple metrics into account for each link simultaneously. The system allows for the inclusion of pruning constraints, and allows for various objectives such as bin packing or load balancing to be achieved.

Abstract: A communication network is provided having source and destination switching routers connected by two different communication paths. A primary label switched path is established on one of the communication paths and a secondary label switched path is established on the other label switched path. The source switching router can be enabled to place one or more data flows within the primary label switched path and can be enabled to place one or more of the same data flows within the secondary label switched path. The destination switching router stores a label identifying each data flow and a forwarding instruction and can be enabled to reference data carried within the primary or secondary LSP with the appropriate data flow label.

Abstract: The invention provides a method which involves inserting probe packets on a per service basis for transmission on a respective round trip; and for each service using the probe packets to calculate packet latency for probe packets which is representative of packet latency for all packets transmitted for the service. In some embodiments, data plane time stamps are used to accurately time probe latency. The invention also provides a method which involves inserting probe packets on a per service basis for transmission on a respective destination network element; and at the destination network element for a given service using the probe packets to calculate one way packet loss for the service.

Abstract: A reliable packet network is constructed with nodes and links where the nodes use a method for fast distribution of link state information. This permits a rapid update of the routing information at all nodes in case of a link failure, minimizing the number of lost packets.

Abstract: A method and system for allocating and controlling a hierarchy of labels in an MPLS network is provided. The hierarchy of labels, inserted into MPLS packets, is introduced so as to correspond to the hierarchy of sub-flows within a data flow. The labels have the established dependency so that positions of labels in the hierarchy identify a sequence of processing the labels and functions associated with the labels. The system for allocating and controlling the hierarchy of MPLS labels includes a first control plane mapper for releasing available labels, a first controller for assigning the released labels according to the hierarchy, means for transmitting the labels in the network, a second controller for detecting the labels, and a second control plane mapper for maintaining current label dependency within the hierarchy. If required, re-addressing of the hierarchy of labels may be performed to maintain flow-sub-flow association throughout two adjacent networks.

Abstract: An extension of a Link Aggregation Protocol (LAP) over the network allows current Ethernet point-to-point LAPs to operate across a Metropolitan Area Network (MAN). A maximum disjoint path algorithm allows selection of a plurality of alternative end-to-end physical routes between two data terminals. These physical routes share a minimum number of nodes and physical links. End-to-end logical links are then formed by a plurality of successive physical links between nodes containing protocol compatible devices, the physical links being selected based on their physical characteristics such as bandwidth and delay. Multiple logical links can be provisioned, without dedicating, between any two data terminals over the network. The logical links provide the virtual point-to-point links that the edge LAP devices require.

Abstract: A routing system and method are provided which use a composite cost in identifying routes. This allows a simple way of identifying the best route taking multiple metrics into account for each link simultaneously. The system allows for the inclusion of pruning constraints, and allows for various objectives such as bin packing or load balancing to be achieved.

Abstract: Methods and network nodes are provided which are adapted to perform protection switching on the basis of raw signal quality information, such as raw BER information, in a manner which instigates the protection switching before an actual failure has occurred. In some embodiments, these methods leverage forward error correction and uncorrected BER to effect traffic redirection before faults are observed at layer 2 and above. This is as opposed to the method of switching layer 2 traffic in response to bitstream characteristics observed at that layer.

Abstract: Methods, systems, computer readable media are provided which facilitate the selection of multiple paths through a network represented by a network topology which take into account shared risk which may exist between network resources. The method involves identifying a first path through the network topology from a source node to a destination node, the first path comprising a first sequence of network resources. For at least one shared risk group, a determination is made if any of the at least one shared risk group includes any of the first sequence of network resources, a shared risk group being a group of network resources within the network topology which have a shared risk. A topology transformation is performed of the network topology into a virtual topology which discourages the use of network resources in any shared risk group determined. A second path through the virtual topology is identified from the source node to the destination.

Abstract: Methods and systems for re-routing a connection through an explicitly routed network. The methods involve initially re-routing the connection to a reduced constraint connection through the network; establishing a fully constrained path through the network; subsequently re-routing the connection to the fully constrained connection through the network.

Abstract: Methods and systems for re-routing a connection through an explicitly routed network. The methods involve initially re-routing the connection to a reduced constraint connection through the network; establishing a fully constrained path through the network; subsequently re-routing the connection to the fully constrained connection through the network.

Abstract: An extension of a Link Aggregation Protocol (LAP) over the network allows current Ethernet point-to-point LAPs to operate across a Metropolitan Area Network (MAN). A maximum disjoint path algorithm allows selection of a plurality of alternative end-to-end physical routes between two data terminals. These physical routes share a minimum number of nodes and physical links. End-to-end logical links are then formed by a plurality of successive physical links between nodes containing protocol compatible devices, the physical links being selected based on their physical characteristics such as bandwidth and delay.

Abstract: A routing system and method are provided which use a composite cost in identifying routes. This allows a simple way of identifying the best route taking multiple metrics into account for each link simultaneously. The system allows for the inclusion of pruning constraints, and allows for various objectives such as bin packing or load balancing to be achieved.

Abstract: A routing system and method are provided which use a composite cost in identifying routes. This allows a simple way of identifying the best route taking multiple metrics into account for each link simultaneously. The system allows for the inclusion of pruning constraints, and allows for various objectives such as bin packing or load balancing to be achieved.

Abstract: Methods and network nodes are provided which are adapted to perform protection switching on the basis of raw signal quality information, such as raw BER information, in a manner which instigates the protection switching before an actual failure has occurred. In some embodiments, these methods leverage forward error correction and uncorrected BER to effect traffic redirection before faults are observed at layer 2 and above. This is as opposed to the method of switching layer 2 traffic in response to bitstream characteristics observed at that layer.

Abstract: The invention provides a method which involves inserting probe packets on a per service basis for transmission on a respective round trip; and for each service using the probe packets to calculate packet latency for probe packets which is representative of packet latency for all packets transmitted for the service. In some embodiments, data plane time stamps are used to accurately time probe latency. The invention also provides a method which involves inserting probe packets on a per service basis for transmission on a respective destination network element; and at the destination network element for a given service using the probe packets to calculate one way packet loss for the service.

Abstract: A communication network is provided which includes a primary label switched path having a plurality of switching routers. The communication network includes a secondary label switched path which extends from a selected primary path switching router, bypasses a section of the primary path and rejoins the primary path at a position downstream of the selected switching router. The selected switching router is conditioned to re-route data intended for transmission on the primary path, onto the secondary communication path in response to a fault on the section of the primary path which is bypassed by the secondary path to restore data transmission.

Abstract: A communication network is provided having source and destination switching routers connected by two different communication paths. A primary label switched path is established on one of the communication paths and a secondary label switched path is established on the other label switched path. The source switching router can be enabled to place one or more data flows within the primary label switched path and can be enabled to place one or more of the same data flows within the secondary label switched path. The destination switching router stores a label identifying each data flow and a forwarding instruction and can be enabled to reference data carried within the primary or secondary LSP with the appropriate data flow label.