Abstract: A method of allocating a wavelength to a lightpath in a wavelength multiplex for use in an optical network comprising nodes connected by optical links, wherein the wavelength multiplex is adapted to support lightpaths of two different bitrates. The disclosed method allows for efficient allocation of wavelengths that prevents wasting bandwidth and mitigates detrimental effects of cross-phase modulation.

Abstract: An optical transmission network comprises nodes which support a plurality of different wavelength channels and support at least a first bitrate traffic type and the second bitrate traffic type on respective wavelength channels. A connection of the second bitrate traffic type is established on an available wavelength, if the wavelength offers an acceptable quality of transmission using a first quality of transmission calculation. Alternatively, a connection of the second bitrate traffic type is established on a wavelength which is spaced, by a guard band, from wavelengths used for connections of the first bitrate traffic type, if the wavelength offers an acceptable quality of transmission using a second quality of transmission calculation. The second quality of transmission calculation is less stringent than the first quality of transmission calculation, and can ignore the effects of interference due to cross-phase modulation.

Abstract: A method of load balancing zero-bandwidth Traffic Engineering Label Switching Paths (0-bw TE LSPs) in a communication network having a plurality of network nodes and a plurality of network links connecting the nodes. The method may be implemented in a centralized Path Computation Element (PCE) or in an ingress router. Each equal cost path from a source node to a destination node is identified from network topology information. A probability of selecting each equal cost shortest path is determined using an iterative Global Load balancing Algorithm (GLA) and each 0-bw TE LSP is provisioned with a specific probability such that the 0-bw TE LSPs are uniformly distributed over all network links.

Abstract: A system, method, and node for a Routing Controller (RC) to obtain from a Path Computation Element (PCE), network resource path metrics across a plurality of domains in a communication network in which each domain includes a plurality of Border Nodes (BNs). The RC sends to the PCE, a first message requesting a first path computation between each pair of BNs. The first message contains a maximum metric-value that a path computation must not exceed for a Path Computation Client (PCC) to consider the path computation acceptable. The RC then sends a second message requesting the PCE to compute a subsequent path computation for each BN pair for which the first path computation did not exceed the maximum metric-value. The second message contains a minimum metric-value that a path metric must exceed for the PCC to consider the path metric acceptable. The RC then receives the computed subsequent path computation.

Abstract: In a multi-domain network each domain, or Autonomous System (AS), has a route calculation entity (PCE A) which is responsible for computing paths between domains on behalf of clients. The route calculation entity (PCE A) sends advertisement messages to a route calculation entity (PCE B) in another domain. The advertisement message carries at least one of: inter-domain resource information and aggregated intra-domain information, such as simplified topology information or cumulative traffic engineering (TE) metrics. The inter-domain resource information can be inter-domain route or reachability information which is normally discarded by a routing protocol such as the Border Gateway Protocol (BGP) and can include inter-domain Traffic Engineering (TE) information such as reservable bandwidth.

Abstract: A method of load balancing zero-bandwidth Traffic Engineering Label Switching Paths (0-bw TE LSPs) in a communication network having a plurality of network nodes and a plurality of network links connecting the nodes. The method may be implemented in a centralized Path Computation Element (PCE) or in an ingress router. Each equal cost path from a source node to a destination node is identified from network topology information. A probability of selecting each equal cost shortest path is determined using an iterative Global Load balancing Algorithm (GLA) and each 0-bw TE LSP is provisioned with a specific probability such that the 0-bw TE LSPs are uniformly distributed over all network links.

Abstract: A method of restoration for an optical network, the network comprising a plurality of nodes (40, 50) interconnected with each other by optical links (130), a subset of the nodes (40) each comprising a regenerator, the method comprising: storing (160) a quality of transmission parameter and a regenerator availability at each of the plurality of nodes (40, 50); notifying (170) a branch node (110) in response to detecting a failure (140) within a link (130) forming part of the path between a source node (20) and a destination node (30), wherein the branch node (110) is the neighbouring upstream node (40, 50) upstream of the link failure (140), the branch node (110) having a regenerator; the branch node (110) computing (190) a restoration segment (100) to a merge node (120) having a regenerator which is a neighbouring downstream node which is downstream of the link failure (140), the restoration path (100) being based on the quality of transmission parameter and regenerator availability information; restoring (18