In this paper we show how modeling and simulating a complex system such as a web-server can help to evaluate di erent metrics and proposals to improve the performance without necessity of using a real system. Many times the system is unavailable or requires spending time and resources to generate results. With simulation and concretely with a coarse-grain simulation as we propose can solve with great success this problem. In this article we have been able to simulate the metric and behaviour of a web server with SSL security, the ellapsed time required by the simulation on a desktop machine is only 1/10 of real time. We have also been able to measure, for example,the performance enhancements with 8 CPUs without having an available machine of similar features.