A method of processing a model of a telecommunications system including a plurality of access nodes through which communications terminals can communicate data is described. The method includes dividing the communications terminals, the access nodes and the core network into different groups, for a first of the groups loading the computer program code representing the communications terminals, the access nodes or the core network of the first group into the computer memory and performing the representing with the processor within a first time period, determining an amount of the data communicated between the first group and one or more of the other groups during the first time period, and for a subsequent time period representing the first group by an amount of data corresponding to the amount of the data communicated between the first group and a second of the groups, whilst loading the computer program code into the computer memory and performing the representing of the second group within the subsequent time period. The results produced by the modeling can be used to configure the telecommunications system itself.