Research On Performance Improvement Of TCP Protocol Based On Explicit Feedback In Wired And Wireless Networks

With the rapid development of network technology, the Internet has gradually evolved into the mobile wireless Internet, which not only provides convenience for the users, but also causes a greater impact on the performance of the existing TCP protocol. In such a network circumstance in which wired and wireless Internet mixed, the reason of the packet loss is not only network congestion, but sudden wireless channel errors, channel attenuation, as well as the switching of mobile devices, and the latter factors may be the main reasons for packet loss in the wireless link. Since the traditional congestion control protocol is mainly made for the wired network, the main reason for packet loss is network congestion. If now the TCP protocol still attributes all packet loss to network congestion and then takes the wrong congestion control mechanism in the side of sender, and the unnecessary reduction of congestion window will be caused, and the performance of TCP be significantly reduced. Therefore, how to accurately learn the network congestion conditions, and correctly distinguish the reasons of packet loss in the wired and wireless hybrid network has become a topic worthy of further study.This paper focus on the TCP problems showed in the wired and wireless hybrid network environment. The main contents as following:1. Firstly, this paper introduces the status and characteristics of wireless networks, the concepts of network congestion as well as the causes, and describes the problems showed by the existing TCP congestion control in the wireless network, and then makes a further study of the performance of TCP in wireless network, describing several kinds of commonly used TCP performance improvement strategy, such as end to end, sub-connection, link layer and cross-layer cooperation. At last, the paper analyzes and evaluates comprehensively their advantages and disadvantages.2. We analyze the insufficient showed by the congestion marking method by the router in the ECN mechanism. This paper proposes a dynamic probabilistic marking method, which combines fuzzy control theory with dynamic probabilistic mark the packets, and will learn more accurate and timely changes in network state, the terminal responses to the congestion marking information more decentralized, and efficiently avoid global synchronization in the TCP streams. 3. Through the long delay wireless link in the hybrid network, the network status showed by the congestion marking information of the intermediate routers is uncertain. For this problem, we further propose in the sender combing the RTT, which can directly reflect the current network situation, taking it as another factor that determines the network status. It will accurately learn the network congestion status, and adopt more reasonable congestion control mechanism, which solve the problem of delay of feedback information, and increase effectiveness and adaptability of the explicit feedback algorithms in the hybrid network.Finally, this paper summarizes what the research have done, and points out the future research directions.