A method of analysing network performance in relation to one or more portions of a network, each network portion comprising a group of nodes, the method comprising: obtaining, in relation to a network portion to be analysed, probe measurements in respect of a plurality of target nodes (40b, 40c, 40d) in the group of nodes in said network portion, respective probe measurements in respect of the respective target nodes in the group each resulting from one or more probe test-messages being sent via a network path from a testing node to the respective target node and one or more associated probe response-messages triggered by receipt and local processing at the respective target node of the one or more probe test-messages being received via a network path from the respective target node by the 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 the respective target nodes; and comparing probe measurements obtained in respect of different target nodes in the group of nodes in said network portion; characterised in that the method further comprises assigning a weighting in respect of at least one of said target nodes in dependence on the comparison; and determining a network performance analysis measure in relation to said network portion according to a predetermined function dependent on at least one probe measurement in respect of at least one of said target nodes in the group of nodes in said network portion and on the weighting determined in respect of said at least one target node. obtaining, in relation to a network portion to be analysed, probe measurements in respect of a plurality of target nodes (40b, 40c, 40d) in the group of nodes in said network portion, respective probe measurements in respect of the respective target nodes in the group each resulting from one or more probe test-messages being sent via a network path from a testing node to the respective target node and one or more associated probe response-messages triggered by receipt and local processing at the respective target node of the one or more probe test-messages being received via a network path from the respective target node by the 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 the respective target nodes; and comparing probe measurements obtained in respect of different target nodes in the group of nodes in said network portion; characterised in that the method further comprises assigning a weighting in respect of at least one of said target nodes in dependence on the comparison; and determining a network performance analysis measure in relation to said network portion according to a predetermined function dependent on at least one probe measurement in respect of at least one of said target nodes in the group of nodes in said network portion and on the weighting determined in respect of said at least one target node.