A method comprising: collecting respective observations of end-end bandwidth experienced on different occasions by multiple past communications occurring over different respective observed paths over a network, each path comprising a respective plurality of network components; modelling each of the respective network components with a bandwidth probability function characterized by one or more parameters; and estimating a component bandwidth or component bandwidth probability density for each of the network components based on the modelling, by determining respective values for said parameters such that a combination of the component bandwidths or bandwidth probability densities for the network components in the observed paths approximately matches, according to an optimization process, the observations of the end-to-end bandwidth experienced by the past communications over the observed paths.