Abstract: A label switched path through a network of nodes, is torn down by sending a message along the path from an ingress node. If there is a fault along the path, a path error message (2) is sent back along the path to the ingress node. The ingress node uses a different route bypassing the fault to alert (3) a further one of the nodes (NE5, NE6) on that path beyond the indicated fault, to cause that further node to continue the tearing down for other nodes on that path beyond the indicated fault by sending a further message (4) along the portion of the path beyond the indicated fault, to indicate to the other nodes to continue the tear down. This enables the ingress node to clean up the rest of the path beyond the fault, to avoid leaving unused capacity unavailable for reuse, and to avoid time consuming manual clean up.

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 connection-oriented optical network (2) comprises nodes (10) and optical links (5) between nodes. Each node (10) has a power control unit (60) for controlling an optical amplifier (43) at the node. A node, in response to a requirement to set up a new connection in the network, signals to a power control unit (60) at each of a plurality of downstream nodes along a path of the new connection to cause the power control unit at the node to adjust the optical amplifier at the node to support a new optical channel to carry the new connection. The node (10) can signal to tear down an existing connection in a similar way. A downstream node determines a number of optical channels for which the optical amplifier can be adjusted concurrently, based on an existing number of active optical channels.

Abstract: A method of configuring a path between an ingress node and an egress node in an optical communications network, the path comprising a first hop and a subsequent hop. The method includes: a) selecting a candidate hop for the first hop of the path; b) obtaining a value of a signal feasibility parameter for the candidate hop; c) determining whether said value lies within an acceptable value range and if one is, accepting said candidate hop for the first hop of the path, and if one is not, repeating steps a. to c.; d) selecting a candidate hop for the subsequent hop of path; e) obtaining a value of a signal feasibility parameter for a combined path comprising the first hop and the candidate hop for the subsequent hop of the path; f) determining whether said value lies within an acceptable value range, if one is, acceptable value range accepting said candidate hop for the subsequent hop of the path, and if one is not, repeating steps d. and e.

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.

Abstract: A network system comprises at least one input TNE (10) and one output TNE (11) interconnected by circuits in the network (20). Each TNE in the protection step comprises a traffic selector (22, 23) switchable between listening to the traffic input from a work circuit (13, 14) and listening to the traffic input from a reset circuit (18, 19) and a Split module (21, 24) allowing sending of a same traffic output either to a work circuit or to a reset circuit. Each TNE comprises in addition an agent (25, 26) termed ASTN agent commanding activation and deactivation of the reset circuit and switching of the traffic selector between work circuit and reset circuit.

Abstract: A connection-oriented network has a first working path (W1) and a second working path (W2). A node (E) receives signalling to allocate resources for a part of a recovery path (R1) for the first working path (W1). The resources are shared by the recovery path (R1) for the first working path and a recovery path (R2a) for the second working path (W2). The node (E) stores an association between the shared resources and a node (A) on the first working path, identified in the signalling, which should be notified when the shared resources are used by the recovery path (R2a) for the second working path (W2). An RSVP-TE <NOTIFY_REQUEST> object in the signalling carries an address of the node to be notified. The node (E) sends an RSVP-TE Notify message to a node (A) on the first working path (W1) which indicates that the shared resources are in use.

Abstract: A method, system and network for routing a multiplexed signal through an optical network (1) comprising nodes (A to F) for routing signals along links (2 to 9) of the network (1), each node (A to F) comprising a lower order matrix (100) and/or a higher order matrix (110). Each matrix (110, 120) is capable of switching segments of the multiplexed signal between interfaces (NL5H) of the matrix (110,120), the lower order matrix (110) capable of switching smaller segments comprising fewer channels than the higher order matrix (120).

Abstract: The present invention relates to configuring the quality of service in a label switched network. In particular, the invention relates to configuring quality of service for the return path of a bi-directional label switched path in a label switched network. The invention provides a method of configuring quality of service for a return path of a bi-directional label switched path within a network, the bi-directional label switched path having a forward path and a return path. A label information context for a quality of service configuration of the return path of a label switched path is configured separately from a quality of service configuration for the forward path. Path set up messages are formed containing a return path quality of service object indicating the quality of service configuration for the return path separately from a quality of service configuration for the forward path.

Abstract: A network comprises nodes connected by optical sections. The nodes support a plurality of traffic types. A candidate optical path having a first traffic type is selected as a routing for at least part of the connection on the basis of at least one routing metric. Pre-computed parameters are retrieved for the optical sections of the candidate optical path. The pre-computed parameters are indicative of quality of transmission along the optical section for the first traffic type. A quality of transmission is determined along the candidate optical path using the retrieved parameters. The pre-computed parameters for each of the optical sections can be used at a network planning tool and then exported to a network management system or a path computation entity at a node for creating a validation module for use in validating connections across the optical transmission network.

Abstract: A network arranged to implement label switched paths, comprising: an ingress label edge router (LER), at least one label switching router (LSR), and an egress LER, in which the ingress LER is connected to the egress LER via one or more of the LSRs. In said network the ingress LER is arranged to transmit, in use, a path message for setting up a bidirectional label switched path (LSP) from the ingress LER to the egress LER via at least one LSR in response for a request for such an LSP. The path message is transmitted over the path of the LSP to be created, in which the path message comprises a first parameter indicative of the bandwidth to be assigned to data traversing the LSP in a first, downstream, direction from ingress LER to egress LER and a second parameter indicative of the bandwidth to be assigned to data traversing the LSP in an opposite, upstream, direction, in which the upstream and downstream bandwidths are different.

Abstract: The invention relates to a method in a border node of an optical network and in an external optical channel originating apparatus and to a border node of an optical network and a router. The invention is particularly applicable to optical path validation in an optical network for an externally originating optical channel. The invention may be used during an optical path fault recovery operation. In the method in a border node of an optical network optical channel traffic parameter associated with an optical channel are received from an optical channel originator external to the optical network. The received optical channel traffic parameters are used to determine the suitability of at least one optical path within the optical network for an externally originating optical channel.

Abstract: A connection-oriented network (5) has a point-to-multipoint working path (10) between a source node (A) and a plurality of destination nodes (B-F). On detection of a failure in the working path, an indication of the failure is sent to a first node (e.g. node A) identifying the point of failure. The indication is sent via a control plane of the network. The first node selects one of a plurality of point-to-multipoint backup paths (21-25) based on the point of failure. Each backup paths connects the first node to the plurality of destination nodes. There is a point-to-multipoint backup path (21-25) for each of a plurality of possible points of failure along the working path. The backup paths (21-25) can be pre-configured to carry traffic in advance of the detection of failure. Alternatively, the first node can signal to nodes of the selected backup path to fully establish the backup path when it is required.

Abstract: Control of a label switched path established in a network is transferred between a management plane and a control plane of the network. A node (e.g., node C) receives a message indicating a change in control of the label switched path, the message identifying the label switched path by a cross-connection identifier corresponding to an entry in the control data stored at the node which identifies data plane ingress and egress segments cross-connected at the node. Control data at the node is updated based on the identified label switched path. The message includes a list of cross-connection identifiers for nodes (e.g., nodes C, E, and F) along the label switched path. The cross-connection identifier can be an mplsXCIndex.

Abstract: A communication network protection system made up of interconnected networks, at least one of which has an automatic control plane (for example ASTN) among which are terminal interconnecting nodes. With the terminal interconnection nodes, termed primary nodes, are associated corresponding secondary terminal nodes wherein a secondary terminal node is used to realize a protection circuit in case of failure of the associated primary node.

Abstract: A method of requesting reservation of a label switched path (LSP) for traffic of a type compatible with ITU-T G709 amendment 3, in an optical transport network by sending a RSVP-TE path message for the reservation of the requested LSP from an ingress node of the requested path, via intermediate nodes along the path to an egress node, and sending a RSVP-TE resv message from the egress node, to cause the nodes to reserve resources for the requested path. The path message has a signal type field having values assigned to indicate traffic types specified in G.709 amendment 3 beyond those specified by G.709 pre amendment 3, without reuse of values specified by G.709 pre amendment 3. Since the nodes along the path can still distinguish in the signal type field any values of the signal type field specified by G.709 pre amendment 3, new nodes can still work with legacy messages.

Abstract: A method of path protection for a connection-oriented packet switched communications network is described using a protection hub in communication with a worker hub via a core protection path. Both the worker hub and the protection hub communicate with at least one provider edge device via a respective worker and protection paths. The method detects a failure in the communications network, indicates the failure to the at least one of the provider edge device, the worker hub, and the protection hub. The method then employs the core protection path if a failure occurs along a worker path is detected, or a worker path and a protection path in parallel if a failure occurs along the core protection path.

Abstract: Setting up a label switched path (LSP) for traffic between nodes of a network, involves sending a request message requesting reservation of resources for the requested LSP, from an ingress node (10) via intermediate nodes (40) and returning an acknowledgement message to an upstream node along the path. Absence of an acknowledgement from the downstream node, that the request message was received, is detected. Whether the given node should react to the detected absence can be determined from an indication (R) in the request message. Thus other nodes can react more quickly to take remedial action, to reroute or to remove the resource reservations without a long wait for a time out or a refresh message from the waiting ingress node, to enable more efficient use of the resources.

Abstract: A data communications system has a plurality of nodes connected by a plurality of links. A subset of the links and nodes forms a worker path for carrying worker data through the communications system, and a further subset of links and nodes provides a protection path for carrying other data in the absence of a fault in the worker path and for providing an alternative path for the worker data in the event of a fault in the worker path. The alternative path is predetermined prior to the detection of a fault in the worker path.

Abstract: A method, system and network for routing a multiplexed signal through an optical network (1) comprising nodes (A to F) for routing signals along links (2 to 9) of the network (1), each node (A to F) comprising a lower order matrix (100) and/or a higher order matrix (110). Each matrix (110, 120) is capable of switching segments of the multiplexed signal between interfaces (NL5H) of the matrix (110,120), the lower order matrix (110) capable of switching smaller segments comprising fewer channels than the higher order matrix (120).