Performance Comparison of Router Assisted Congestion Control Protocols: XCP vs. RCP

In the current Internet, network overload is prevented by the congestion control of the Transmission Control Protocol (TCP). The traditional TCP congestion control is an endto- end mechanism that suffers from some inherent shortcomings. A design alternative for the Future Internet is to use more feedback from the routers. Such router-assisted congestion control schemes can achieve a more effcient utilization of network resources and better fairness, even in environments with large bandwidth-delay products. Two promising proposals are the eXplicit Control Protocol (XCP) and the Rate Control Protocol (RCP). This paper evaluates the performance of XCP and RCP and compares them with the existing TCP congestion control. In order to verify previous work, a new simulation tool has been developed independently of the existing ns-2 code basis. This simulator is used to study the basic behavior of the algorithms and to analyze several degrees of freedom in the protocol design. Furthermore, the performance of the different approaches is compared using realistic Internet traffc scenarios. The results show that indeed both XCP and RCP effciently utilize the link capacity without requiring packet loss. Unlike XCP, RCP improves the reactivity of data transfers by reducing the ow completion time. These results confrm previously published results and show that in particular RCP has the potential to replace TCP congestion control in the Future Internet.