Abstract: An arrangement and method for analysing the data transferred in communications networks. The fact that though the amount of user plane traffic and data is increasing fast, the amount of signalling traffic is hardly increasing at all, is utilised. In the present system the analysis of the user plane and the control plane is done separately in user plane analysis appliance (206) and protocol analyser (204). The separate analysis results are then combined by certain criteria and the combined data is shown. An at least nearly real-time network data analysis is possible also in the networks with high speed traffic.