【作者】 潘亚军；

【导师】 李忠诚； 刘金刚；

【作者基本信息】 首都师范大学 ， 计算机应用技术， 2005， 硕士

【摘要】 TCP协议是TCP/IP协议族中两个重要的传输协议之一,目前IP网络上承载的大部分应用的流量都是通过TCP来传输的。TCP吞吐量作为描述TCP性能的一个重要的端到端的网络性能参数,是研究和分析TCP行为和性能的一个重要指标。对TCP吞吐量进行测量有助于在应用层调整QoS,从而提高服务质量,并能促进QoS Routing技术和端到端多播拥塞控制协议的研究。 目前已有的TCP吞吐量的测量方法和手段会产生大量测试流量,对网络造成较大影响,不适合在高速网络和长期在线测量环境下使用。本论文详细介绍和分析了相关的测量方法和测量工具,并区分了带宽和吞吐量等极易混淆的术语。为了避免直接测量方法的不足,本论文提出了一种利用TCP吞吐量分析模型的间接测量方法。本论文在详细分析了已有的一些TCP吞吐量分析模型的基础上,利用Gilbert模型来描述端到端路径上的丢包行为,根据TCP的拥塞控制机制对TCP的拥塞控制过程进行建模。在建立的分析模型的基础上提出了一个测量算法。NS2的仿真实验表明,新模型相对于已有的分析模型能够更加精确地反映TCP吞吐量的大小和变化趋势。本文提出的测量算法具有以下特点: (1) 无需被测端的协作。该算法只需要对端到端路径的往返延迟和丢包率、接收方通告的最大窗口和最大段大小等参数进行测量,因此测量只需要在测试端运行测量工具,而不需要被测端的协助;(2) 适用于各种带宽的IP网络。由于该算法是采用基于TCP拥塞控制机制的吞吐量分析模型来进行间接测量,因此不需要产生大量的测量数据包。它通过捕获TCP连接建立阶段的ACK报文,可以支持不同带宽IP网络的TCP发送窗口;(3) 适合长期在线测量。由于只需测量一些端到端的路径参数如往返延迟和丢包率,因此不需要产生很大的测量流量,对网络几乎不造成任何影响,可以很好地支持长期在线测量。 此外,本论文的工作还包括开发一个大型的分布式网络监测分析系统NetTurbo。该系统集成了主动测量和被动测量这两种技术,采用分布式采集测试、集中式分析的框架,保证不同时间刻度、2-7层深层次流量与网络性能分析。并且基于本论文设计的算法实现的TCP吞吐量的测量工具已经被应用于该系统中。更多还原

【Abstract】 The TCP transport protocol is one of two important transport protocols in TCP/IP protocol stack. A significant amount of today’s Internet traffic is carried by TCP. As an important end-to-end internet performance parameter, TCP throughput is an important index of study and analyzing TCP behavior and performance. Measuring TCP throughput will be helpful for adjusting QoS at applicational layer so as to improve the quality of services. Besides that, the study on Measuring TCP throughput will also promote the studies of QoS routing and end-to-end multicast congestion control protocol.Some methods and tools have been developed to measure TCP throughput. However, these tools will produce large measurement traffic. If being used incorrectly, these methods will have large impact on network. So they are not suitable for high speed network or on-line measurement environment. In this thesis, we introduce and analyze relevant measurement methods and survey tools in detail. We also distinguish such terms extremely apt to obscure as the bandwidth and throughput, etc. To avoid disadvantages of direct measurement method, a new method is proposed, which measures TCP throughput indirectly with a TCP throughput analysis model. Based on detailed analysis for some TCP throughput analysis models, this dissertation uses the Gilbert two-state model to represent the packet lost behavior of end-to-end internet path and builds a model for TCP congestion control process according to TCP congestion control mechanism. Furthermore, a new measurement algorithm is presented based on the proposed analysis model. The experiments of NS2 Simulation indicate that the new model can measure TCP throughput and its change trend more precisely than those old models. The proposed model in this paper has three characteristics as following: (1) It doesn’t need the cooperation of destination nodes. The algorithm only requires source nodes to measure some metrics of end-to-end internet path, such as RTT, packet loss rate, maximum announced window by receivers, MSS and so on. So the measurement only needs to run the measurement tool on source nodes, and needn’t the cooperation of destination nodes. (2) It’s suitable for IP networks with various banswidth. Because this algorithm uses the analysis model based on TCP congestion control mechanism to measure TCP throughput indirectly, it need not to send many measurement data packets. By capturing the ACK packets in the TCP connectionestablished phase, the algorithm can support all kinds of TCP windows announced by receivers in different bandwith IP network. (3) The algorithm is also suitable for a long period on-line measurement. Due to only measuring some end-to-end internet path parameters such as RTT and packet loss rate, it doesn’t produce large measurement traffic. So it has little impact on network and can support on-line measurement in a long period.Besides these, we have developed a large-scale distributed network measurement and analysis system (NetTurbo).This system integrats active mearsurement and passive measurement techonlogies. It uses a frame of distributed collection and centralized analysis to support traffic and performace analysis of 2-7 layer in various time scales. And a TCP throughput measurement tool using the proposed algorithm has been realized for the system.更多还原