The desire to improve the overall performance of IP network leads to designing new QoS achitectures. The new Enhancement in providing quality of service (QoS) on the Internet is based on the Different Services (DiffServ). DiffServ divides traffic into small classes and allocates network resources on a per-class basis. In this architecture, packets are marked with different DiffServ code points (DSCP) at edge routers, and the priority for packets is given via the value of this field. On the other hand, MPLS is a fast forwarding mechanism that depends on Label's. The main advantage of MPLS is its support for traffic engineering which results in best utilization of network's resources like link capacity. The integration of using MPLS (as a forwarding mechanism) with DiffServ (as a QoS mechanism) offer high Quality of service especially for real time applications (such as VoIP, Video Conference). We evaluate the performance of MPLS-DiffServ networks in our research. We study QoS metrics as delay, variation of delay, upload response time, link utilization, packet loss for several kinds of traffic (Voice, Video, FTP) by using OPNET Simulator and we showed its superiority over MPLS network and pure IP ones. We compare our results with MPLS networks and pure IP ones. Our results showed superiority of MPLS-DiffServ over other kinds of networks. This is clear in decreasing delay ,delay variation, upload response time, queuing delay, reduction of lost packets and best utilization of link capacity.