The quality of service is a need in recent computer network developments.The present paper evaluates some characteristics in a proposed network topology such as dropped packets and bandwidth use, using two traffic sources, firstly a VoIP source over an UDP agent, then a CBR traffic source over an UDP agent as well as the previous one.Two possible configurations are proposed, implementing both of them in the Network Simulator, and implementing in one of them differentiated services to compare the results.Statistics results are shown, in both cases showing the accumulative dropped packet number and the throughput in the link, obtaining a reducer number of dropped packets in the stage with differentiated services, and an improvement in the bandwidth use.