More detail is needed here, are you planning to use the simulation models to evaluate the new infrastructure performance?, in that case OMNET or OPNET could be a suitable frameworks to analyze this.
Hi, if you're still needing some help, there's one open source solution NS2 (Network Simulator). There's a lot more networking simulators.. and it's available one list on http://people.idsia.ch/~andrea/sim/simnet.html