An evaluation of the performance advantage of Diffserv with respect to voice over IP flows

In this paper, we study the network queuing effects on the VoIP delay and jitter. Two service polices, FIFO and Differentiated Service (DiffServ), are studied with repect to the queuing delays of VoIP packets. First, we present our assumptions for delay characterization. Then, we provide a model for the traffic flow. We create a ¿Markovian+Deterministic (M+D)¿ model in order to represent the traffic flow as a combination of periodic VoIP deliveries and Markovian ¿background¿ traffic. We then simulate the system and evaluate the performance of DiffServ and FIFO for VoIP flows under various the traffic intensities and a varied number of routers. The simulation results show that FIFO queuing introduces larger delay jitter as the background traffic intensity approaches the router's processing capacity. However, DiffServ can efficiently confine the VoIP jitter level at each hop and limit the growth within accepted VoIP delay requirements over a series of routers.