Assisted determination of data flows in communication/data networks

There is provided a method of determining data flow in a network, the method comprising: (a) selecting a location within the network for providing a data processing means adapted to process data pertaining to the network data flow; (b) determining the expense and/or level of data capture that would result from providing the data processing means at the selected location; and (c) providing the data processing means at the selected location dependent on the determination in step (b) and predetermined expense and/or data capture targets. This method can be used to select points inside the core of a network for data capture of flows routed through them in order to construct the traffic matrix of the network. This method has a number of advantages over known methods of obtaining the traffic matrix of a data network. In particular, it can be used for different use cases, maximizing the capture level for a given investment or finding the minimal investment to achieve a given capture level.