The telecommunications industry is currently moving towards the trade of Internet services. However, with the extension in terms of enterprises sites, the quality of transported traffic can be influenced. Given that the nature of deployed application vary periodically and become more and more demanding in terms of delays, the scalability need can lead to a dysfunction of the latter. In this paper, we will measure and evaluate the impact of multiples clients on the performances of the network and the transported applications. This study was done under the Riverbed Modeler simulator. The traffics used for the simulations is Voice over IP (VoIP). The evaluation criteria are on the jitter, the end-to-end delay, and the VoIP loss rate.