| In today's high-speed packet networks that support various applications with different service requirements, congestion control is an important issue. One of the methods for preventing congestion is packet scheduling [14]. Packet scheduling in network routers can provide guaranteed performance in terms of delay, delay jitter, packet loss, and throughput.; The main objective of this thesis is to implement a model for the VirtualClock scheduling mechanism, perform a simulation based performance analysis of the VirtualClock algorithm, and compare it to three commonly used scheduling mechanisms: WFQ, Custom Queuing, and Priority Queuing. The VirtualClock algorithm monitors the average transmission rate of packet data flows. It also provides each flow with a guaranteed throughput and a low queuing delay.; We implement a scheduler model for VirtualClock and incorporate it into the EP layer output queues of an EP router using OPNET simulation tool. We measure the performance of the algorithms in terms of fairness, end-to-end delay, and amount of packet loss from different traffic flows during various time periods. We also simulate a network running several Internet applications: HTTP, FTP, IP Telephony, and videoconferencing and we observe the impact of scheduling algorithms on the performance of these applications. Our simulation results indicate similarities of VirtualClock to WFQ and to Custom Queuing. They also illustrate the differences between VirtualClock and Priority Queuing. |
