A method of analysing network performance of a network comprising a plurality of network nodes, the method comprising, in respect of at least one target node: obtaining a plurality of probe measurements, the probe measurements in respect of said target node including: - at least one first-path probe measurement resulting from one or more probe test-messages being sent via a first network path from a testing node to said target node and one or more associated probe response-messages triggered by receipt and local processing at said target node of the one or more probe test-message being received from said target node by said testing node; and - at least one other-path probe measurement resulting from one or more probe test-messages being sent via at least one other network path from a testing node to said target node and one or more associated probe response-messages triggered by receipt and local processing at said target node of the one or more probe test-messages being received from the target node by said testing node; the respective probe measurements each relating to one or more network performance characteristics in respect of the network paths taken by the respective probe test-messages and the probe response-messages associated therewith and being dependent also on the local processing of the respective probe test-messages at said target node; characterised in that the method further comprises determining respective measures of unexpectedness in respect of said at least one first-path probe measurement and in respect of said at least one other-path probe measurement, said measures of unexpectedness being determined according to a predetermined function of said respective probe measurements; comparing said respective measures of unexpectedness and in dependence on the comparison, assigning a weighting in respect of said target node; and: determining a network performance analysis measure according to a predetermined function dependent on at least one probe measurement in respect of at least one target node and on the weighting assigned in respect of said at least one target node. obtaining a plurality of probe measurements, the probe measurements in respect of said target node including: - at least one first-path probe measurement resulting from one or more probe test-messages being sent via a first network path from a testing node to said target node and one or more associated probe response-messages triggered by receipt and local processing at said target node of the one or more probe test-message being received from said target node by said testing node; and - at least one other-path probe measurement resulting from one or more probe test-messages being sent via at least one other network path from a testing node to said target node and one or more associated probe response-messages triggered by receipt and local processing at said target node of the one or more probe test-messages being received from the target node by said testing node; the respective probe measurements each relating to one or more network performance characteristics in respect of the network paths taken by the respective probe test-messages and the probe response-messages associated therewith and being dependent also on the local processing of the respective probe test-messages at said target node; - at least one first-path probe measurement resulting from one or more probe test-messages being sent via a first network path from a testing node to said target node and one or more associated probe response-messages triggered by receipt and local processing at said target node of the one or more probe test-message being received from said target node by said testing node; and - at least one other-path probe measurement resulting from one or more probe test-messages being sent via at least one other network path from a testing node to said target node and one or more associated probe response-messages triggered by receipt and local processing at said target node of the one or more probe test-messages being received from the target node by said testing node; characterised in that the method further comprises determining respective measures of unexpectedness in respect of said at least one first-path probe measurement and in respect of said at least one other-path probe measurement, said measures of unexpectedness being determined according to a predetermined function of said respective probe measurements; comparing said respective measures of unexpectedness and in dependence on the comparison, assigning a weighting in respect of said target node; and: determining a network performance analysis measure according to a predetermined function dependent on at least one probe measurement in respect of at least one target node and on the weighting assigned in respect of said at least one target node.