This paper has described the simulation model of the EDPEPPS environment. The modularity of the model allows a re-configuration of the parallel platform (e.g. the resource layer can be extended to model other networks such as Fast Ethernet of FDDI). The toolset supports graphical design, performance prediction through modelling and simulation, and visualisation of predicted program behaviour. The success of the toolset depends mainly on the accuracy to predict performance. Therefore, the user will be able to compare design alternatives. The validation of the entire model is based on the COMMS1 benchmark and the parallelisation of the H.261 algorithm. The parallel platform parameters have been obtained by measuring the real system. Currently, there is a tool which supports the automatic evaluation of these parameters. A useful feature is to predict performance on hypothetic machines where resources can be increased as well as to perform scalability analysis. During a real execution, it is difficult to control the external workload affecting the performance of a parallel application. In the simulation context, external workload generated by other applications requiring computation power or communication facility can be controlled.