Abstract: A method of providing state synchronization between a controller and a switch in a communications network, wherein the controller provides flow data for routing flows through the switch and transmits, in flow modification messages, the flow data to the switch for storage in flow tables, the state synchronization comprising ensuring that flow data in the flow tables of the switch are consistent with the flow data provided by the controller. The method comprises, by the controller (19), providing (21) an identifier in each flow modification message.

Abstract: A method of providing state synchronization between a controller and a switch in a communications network, wherein the controller provides flow data for routing flows through the switch and transmits, in flow modification messages, the flow data to the switch for storage in flow tables, the state synchronization comprising ensuring that flow data in the flow tables of the switch are consistent with the flow data provided by the controller. The method comprises, by the controller (19), providing (21) an identifier in each flow modification message.

Abstract: A connection-oriented communications network comprises a plurality of interconnected nodes. A traffic path can be set up across the network. Path delay data is obtained for the traffic path by using control plane signalling messages (e.g. a Resource Reservation Protocol-Traffic Engineering, RSVP-TE signalling message) between nodes of the traffic path. The path delay data can be path delay asymmetry data indicative of an asymmetry in path delay between a forward transmission direction and a reverse transmission direction of the traffic path. Each intermediate node along the traffic path can form a signalling message for forwarding to the downstream node which includes one or more values of path delay incurred by that node, or an accumulated path delay value. The path delay can result from one or more of mapping delay, Forward Error Correction (FEC) coding and propagation delay.

Abstract: A method (10) of routing communications traffic packets across a communications network comprising a plurality of nodes and a plurality of links interconnecting respective pairs of the nodes, the method comprising steps: a) for links of the network, obtaining a respective plurality of measurements of a parameter indicative of a quality of forwarding communications traffic packets across the link (12); b) for each said link, calculating from the respective plurality of measurements of the parameter an index indicative of a percentage of the respective plurality of measurements of the parameter for which the parameter satisfies a preselected threshold value of the parameter (14); and c) selecting a path for communications traffic packets across the communications network by selecting links for the path based on the respective index of each said link (16).

Abstract: A connection-oriented communications network comprises a plurality of interconnected nodes. A traffic path can be set up across the network. Path delay data is obtained for the traffic path by using control plane signalling messages (e.g. a Resource Reservation Protocol-Traffic Engineering, RSVP-TE signalling message) between nodes of the traffic path. The path delay data can be path delay asymmetry data indicative of an asymmetry in path delay between a forward transmission direction and a reverse transmission direction of the traffic path. Each intermediate node along the traffic path can form a signalling message for forwarding to the downstream node which includes one or more values of path delay incurred by that node, or an accumulated path delay value. The path delay can result from one or more of mapping delay, Forward Error Correction (FEC) coding and propagation delay.

Abstract: A method in a node of a network comprises the steps of receiving a configuration command signal, the configuration command signal indicating that one or more configuration parameters are to be changed in the node and at least one other node of the network. A routing protocol message is modified to include the configuration command signal. The configuration command signal is communicated to the at least one other node of the network using the modified routing protocol message.

Abstract: A node for a telecommunications network has a switch and a controller, for setting up a circuit along a main path through the network. The circuit associated with one or more precalculated alternate paths, for use in the event of failure of the main path. A check is made of whether one or more of the precalculated alternate paths is currently valid, based on whether the network resources needed by the alternate paths are currently available, according to a local dynamically updated routing database. If valid, then the controller sets up the switch and communicates with other nodes to set up one of the alternate paths for that circuit. This can reduce the chance of rerouting delay caused by the setting up of the alternate path failing owing to its resources no longer being available. Checking the precalculated path is still quicker than calculating an alternate path dynamically when needed.

Abstract: A method of generating network topology parameters of a communications network domain comprising a plurality of network nodes and a plurality of interconnecting links. The method comprises: identifying network nodes configured to interface with one or more other network domains as summarized nodes; and generating network topology parameters for one or more pairs of summarized nodes. The network topology parameters are dependent on the transmission parameters of one or more identified paths between said pair of summarized nodes. At least one said path comprises at least one other network node and respective interconnecting links.

Abstract: The present invention relates to methods and node entities for distributing Physical (PI) parameters used when establishing Optical Paths for user traffic by routing and wavelength assignment of optical channels carried in optical links of a Wavelength Switched Optical Network (WSON).

Abstract: A method of generating network topology parameters of a communications network domain comprising a plurality of network nodes and a plurality of interconnecting links. The method comprises: identifying network nodes configured to interface with one or more other network domains as summarized nodes; and generating network topology parameters for one or more pairs of summarized nodes. The network topology parameters are dependent on the transmission parameters of one or more identified paths between said pair of summarized nodes. At least one said path comprises at least one other network node and respective interconnecting links.