Improved Investigations On XCP

With the rapidly improvement of computer network, the increase of Internet users, the popularity of multimedia flow, problem of Internet congestion control becomes more and more serious. Congestion control is the key factor to assure the Internet robustness. It becomes the hot issue and difficulty issue of the Internet research.. TCP as the most wildly used transmission protocol, it is a kind of end-to-end protocol. It takes the network or the Internet as a black box and can't know the network status directly. It only can deduce the network status by end system . Current TCP_based congestion control exhibits poor performance in environments with a large per-flow bandwidth-delay product . As a remedy, Dina Katabi propose the eXplicit Control Protocol (XCP), a congestion control protocol that embodies the principle of decoupling congestion control from bandwidth allocation and uses this decoupling to achieve good performance in high bandwidth-delay networks. XCP provides a joint design of the end systems and the router and is characterized by the existence of separate congestion/efficiency controller and fairness controller at the router. XCP outperforms TCP both in traditional environments and in high bandwidth-delay product networks. Further, XCP maintains TCP's scalability and robustness, and can provide a variety of qualities of service. We compared the performance, stability, and feasibility of XCP with other protocol and concluded XCP is an excellent protocol which provided with good performance, reasonable design, and feasibility. We considered it as the powerful candidate of the future high bandwidth-delay networks and choosed it to research one step more. Our research work include two aspects mainly: 1. Firstly, adding the admission control at the XCP receiver. High bandwidth-delay networks are environments where the per-flow bandwidth can reach a few Gbit/s, then the receiver's speed should be taken into account. Aiming at this destination, we adjust the structure of the receiver system, adding the admission control. The receiver can modify the Feedback field to express the allowable speed. Then the field Feedback can reflect the whole network status, including the sender, the link on the path and the receiver. After such improvement, partial of traffic control function integrated into congestion control. It make traffic control more simple andclearly and cancel the field window in traffic control.2.Secondly, based on the research of the parameter of XCP, we discover that parameterinfecting the network utilization obviously, parameterinfecting the time of empting queuein the router, parameterinfecting the time of converging to system fairness status. All thethree parameter are the trade-off between of efficiency and stability. The utilization ofbackbone is not very high normally in fact. Parameterinfecting the network utilizationobviously, so through adjusting parameterin different situation to advanced theperformance of network. When the system is more stable and the utilization is not very high,we adjust the parameterhigher, contrarily, we adjust the parameterlower. Weuse the average queue to judge the system's stability. Experiments prove thatimprovements make system more efficiency and maintain the stability.we use software Net Simulator-2 to complete experiments in this paper and use control theoryto analyzing the system stability.