Abstract: In one example aspect, a method is provided for tearing down a label switched path (LSP) through a communications network. The method comprises sending a first message towards an egress node of the LSP informing nodes of the LSP and the egress node of a tear down of the LSP, determining that one of the nodes of the LSP has not forwarded the first message along the LSP, and sending a second message to a controller of the communications network to cause the controller to communicate directly with one of the nodes to inform the one of the nodes of the tear down of the LSP.

Abstract: In one example aspect, a method is provided for tearing down a label switched path (LSP) through a communications network. The method comprises sending a first message towards an egress node of the LSP informing nodes of the LSP and the egress node of a tear down of the LSP, determining that one of the nodes of the LSP has not forwarded the first message along the LSP, and sending a second message to a controller of the communications network to cause the controller to communicate directly with one of the nodes to inform the one of the nodes of the tear down of the LSP.

Abstract: A method for routing packet traffic through a network comprising a plurality of network nodes supporting RSVP-TE protocol and Segment Routing protocol. Each of the two protocols is associated with a separate set of labels, the method comprises calculating (202) a path through the network; checking support (204) for both protocols at nodes along the calculated path and encoding (206) the calculated path as a set of Adjacency Segment Identifiers. The method also comprises optimising (208) a label stack of the calculated path by substituting more than one adjacency SIDs with a node SID if a partial path identified by the substituted adjacency SIDs equals a shortest path. If all nodes along the calculated path support label stack depth equal to or deeper than the optimised label stack (210) then segment routing is used to set up the path.

Abstract: A method and a network node for managing allocation of network resources in restoration of traffic in a connection oriented network are disclosed. The method comprises restoring a first traffic from a first path on an alternative path if the first path is affected by a first failure and assigning a reserved status to resources of the first path no longer used for carrying the first traffic. If a second path is affected by a second failure the method comprises restoring a second traffic from the second path, wherein the restoration of the second traffic does not use the resources having the reserved status.

Abstract: The present invention provides a method for enabling Segment Routing in a multi-domain network comprising a client network domain and a server network domain, where the client network domain is a packet network domain and the server network domain is a connected-oriented network domain. The method comprises assigning a network segment identifier to each of one or more potential paths through the server network domain between a pair of overlay network nodes in the client network domain, wherein the one or more potential paths are not pre-configured and the or each network segment identifier is suitable for inclusion in one or more data packets to indicate to at least one of the pair of overlay network nodes a preselected network segment routing for the one or more data packets. The present invention further provides a method for routing data packets in the multi-domain network.

Abstract: A method for routing packet traffic through a network comprising a plurality of network nodes supporting RSVP-TE protocol and Segment Routing protocol. Each of the two protocols is associated with a separate set of labels, the method comprises calculating (202) a path through the network; checking support (204) for both protocols at nodes along the calculated path and encoding (206) the calculated path as a set of Adjacency Segment Identifiers. The method also comprises optimising (208) a label stack of the calculated path by substituting more than one adjacency SIDs with a node SID if a partial path identified by the substituted adjacency SIDs equals a shortest path. If all nodes along the calculated path support label stack depth equal to or deeper than the optimised label stack (210) then segment routing is used to set up the path.

Abstract: A connection-oriented network has a working path and a segment recovery path for a segment of the working path. The working path has a branch node at an end of the segment where the segment recovery path connects to the working path. The branch node is not located at an end node of the working path. Control plane signalling is received at an end node of the working path from a node along the working path, indicating that a failure has occurred along the working path. The end node determines, from the received control plane signalling, if the failure has occurred outside the segment of the working path. When it is determined that the failure has occurred outside the segment of the working path, a notification is sent to the branch node. The notification is an instruction not to reroute to the segment recovery path.

Abstract: A method and a network node for managing allocation of network resources in restoration of traffic in a connection oriented network are disclosed. The method comprises restoring a first traffic from a first path on an alternative path if the first path is affected by a first failure and assigning a reserved status to resources of the first path no longer used for carrying the first traffic. If a second path is affected by a second failure the method comprises restoring a second traffic from the second path, wherein the restoration of the second traffic does not use the resources having the reserved status.

Abstract: A method and a network node for managing allocation of network resources in restoration of traffic in a connection oriented network are disclosed. The method comprises restoring a first traffic from a first path on an alternative path if the first path is affected by a first failure and assigning a reserved status to resources of the first path no longer used for carrying the first traffic. If a second path is affected by a second failure the method comprises restoring a second traffic from the second path, wherein the restoration of the second traffic does not use the resources having the reserved status.

Abstract: The present invention provides a method for enabling Segment Routing in a multi-domain network comprising a client network domain and a server network domain, where the client network domain is a packet network domain and the server network domain is a connected-oriented network domain. The method comprises assigning a network segment identifier to each of one or more potential paths through the server network domain between a pair of overlay network nodes in the client network domain, wherein the one or more potential paths are not pre-configured and the or each network segment identifier is suitable for inclusion in one or more data packets to indicate to at least one of the pair of overlay network nodes a preselected network segment routing for the one or more data packets. The present invention further provides a method for routing data packets in the multi-domain network.

Abstract: A method of realigning a node in a label switched network comprising a plurality of nodes and a node with a processor, a memory, and a network interface, for carrying out the method. The method includes periodically maintaining backup path status information for the node, restarting the node, and re-establishing label switched paths with the plurality of nodes using the backup status information. Communication with adjacent nodes is carried out in order to reconcile the path status information with respective path status information in the adjacent nodes in order to establish node realignment preferably judged against a threshold value for path reliability.

Abstract: A method and a network node for managing allocation of network resources in restoration of traffic in a connection oriented network are disclosed. The method comprises restoring a first traffic from a first path on an alternative path if the first path is affected by a first failure and assigning a reserved status to resources of the first path no longer used for carrying the first traffic. If a second path is affected by a second failure the method comprises restoring a second traffic from the second path, wherein the restoration of the second traffic does not use the resources having the reserved status.

Abstract: A method for setting up a new path for carrying traffic between border nodes of a client communications network through a server communications network. The method comprises, at a border node of the client communications network: receiving a request for reservation of resources from a first client node of the client communications network; determining that the border node does not have a path for carrying traffic through the server communications network having sufficient resources to meet the request; and, in response, initiating set up of a new path for carrying traffic between border nodes of the client communications network through the server communications network.

Abstract: A network element for a communications network having decoupled control and data planes may be in either a first state, the control plane and data plane are configured to interact, whereas, in the second state, the network element suppresses a control message for the data plane such that the configuration of the data plane is preserved. Accordingly, the network element may be in a second state when the data plane is undergoing maintenance such that there is no interaction between the control and data planes.

Abstract: In a communications network, a recovery segment is used to reroute a recoverable part of a path set up along an original route along links between nodes. When a defect is detected in the original route of the path, but is undetectable by nodes within the recoverable part, a reroute message is sent (5) from outside the recoverable part to an end node (N2,N4) of the recoverable part. This prompts the rerouting of the recoverable part over the recovery segment. Thus segment recovery becomes possible for these defects which cannot be detected at nodes in the segment. This extends the applicability of benefits of segment recovery such as reduced resources devoted to recovery, and flexibility to choose which parts of paths to protect. The end node can send a notify message beforehand, to request (3) notification of the defect as the reroute message.

Abstract: A method of operating a control plane having a centralised network management system (10), control domain servers (20) and a plurality of forwarding elements (30), for controlling respective network entities (L2), and grouped into control domains (21, 22, 23). Each domain has a control domain server. Automatic checking for inconsistencies (110, 115, 210, 310, 320, 450) between the records held at the different parts of the control plane, involves comparing checklists of the records of the circuits stored at the different parts of the control plane. If an inconsistency is found, there is automatic updating (120, 220, 230, 460) of the records using a copy sent from another of the parts of the control plane. The checklists can avoid the need to forwarding entire copies.

Abstract: A connection-oriented network has a working path and a segment recovery path for a segment of the working path. The working path has a branch node at an end of the segment where the segment recovery path connects to the working path. The branch node is not located at an end node of the working path. Control plane signalling is received at an end node of the working path from a node along the working path, indicating that a failure has occurred along the working path. The end node determines, from the received control plane signalling, if the failure has occurred outside the segment of the working path. When it is determined that the failure has occurred outside the segment of the working path, a notification is sent to the branch node. The notification is an instruction not to reroute to the segment recovery path.

Abstract: A node (100) for a communications network having a control plane distributed across multiple nodes, the node having a controller (20) arranged to run protocols of the control plane and an event logger (10) for logging events in the operation of the control plane protocols at the node. A local timing reference (30) in the node is synchronised to a common network clock, and an interface is provided for the event logger to communicate with an external log server at a different location. The event logger is arranged to use the local timing reference to determine a time for each logged event and to send an indication to the external log server of the logged events and their times. By timing events based on a common network clock, the log server can then determine a relative timing of events at different nodes more accurately, and thus facilitate tracing of events through the network.

Abstract: A node for use in a photonic network comprises an optical to electrical interface for receiving a traffic signal and an electrical to optical interface for outputting a traffic signal. A processor is adapted, in response to receiving a control plane message, to reconfigure at least one feature of an optical-to-electrical-to-optical conversion process carried out in the node, according to a type of traffic signal identified by the control plane message.