TCP is an important communication protocol as more and more multimedia technologies are deployed in the Internet nowadays. However, existing TCP control mechanism has some shortcomings in supporting real-time streaming traffic. Although UDP can be used as an alternative to transmit real-time application data, it lacks congestion control. Introducing a new TCP-friendly protocol that supports the multimedia applications as well as congestion control has been the aim for many researchers for a long time. The transport layer protocol DCCP was designed to reach this goal recently. Another challenge in high bandwidth-delay product networks is to achieve a fair bandwidth allocation with efficiency, while minimizing packet loss and bottleneck queue. As a simple and low-complexity protocol, VCP can meet this challenge by leveraging the two ECN bits in network congestion feedback. In this paper, we study and implement the VCP controller in a bottleneck network with DCCP traffic. We use VCP to analyze the traffic load into different congestion states in order to effect congestion avoidance and control in the presence of huge DCCP-CCID2 traffic. We perform mathematical analysis and run OPNET simulation to validate our DCCP/VCP controller. We compare the performance of DCCP/VCP with TCP/RED, DCCP/RED and TCP/VCP in a bottleneck network. Our simulation results show that VCP controller can provide DCCP flows with a smooth throughput, a small queue size and a low packet drop rate.
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