基于速率的网络拥塞控制协议若干技术研究

发布时间：2018-04-08 08:25

本文选题：拥塞控制　切入点：速率控制协议　出处：《宁波大学》2015年硕士论文

【摘要】：随着网络技术的快速发展,互联网已经成为人们生活不可缺少的一部分。虽然随着网络硬件技术的发展网络带宽不断增大,但是网络资源总是有限的,由于网络中资源和流量的分布不均匀,网络拥塞的发生就成了互联网的固有属性。为了增加互联网的带宽利用率、提高互联网的稳定性,需要执行拥塞控制。根据拥塞控制算法运行的位置,可以分成源算法和链路算法。源算法只涉及网络边缘设备,根据网络边缘设备获取的信息调整数据发送速率,如TCP中的拥塞控制机制就是利用网络端主机获取的信息来预测网络拥塞的发生;链路算法则是通过数据包头收集网络设备的拥塞信息,将此信息写入数据包,并将拥塞信息反馈给端主机来检测拥塞的发生,如显式拥塞控制算法。传统的拥塞控制机制往往是通过TCP及TCP改进协议来实现,随着互联网技术的发展,此机制暴露了许多局限性。本文分析目前TCP拥塞控制机制的基本原理,包括慢启动、拥塞避免、快速回复和快速重传机制,以及一些TCP拥塞控制改进协议,如TCP Westwood、TCP Vegas、HSTCP等,发现TCP的窗口减小方式在高速网络上的性能严重下降,且无线网络中因信道误码率无法充分利用带宽。针对这些问题,通过对显式拥塞控制机制分析,本文进行了基于RCP(Rate Control Protocol)的精确速率反馈拥塞控制算法研究,并针对无线网络提出一种基于带宽估计的速率反馈拥塞控制方案,最后提出一种基于速率的MPTCP拥塞控制方案。本文的具体的研究内容如下。(1)深入分析了RCP协议的拥塞控制方式,其使用链路容量除以前一时刻的速率来估计当前流数量,在短数据流较多且数据流数量变化较大的场景下这种估计方法有一定限制,此时RCP协议会由于其计算通过路由器的数据流数量偏差较大,造成反馈速率计算不准确。针对这个问题,提出了一种基于RCP协议的精确速率反馈拥塞控制算法,该算法略去了估计通过路由器的流数量,就能精确计算出反馈速率,并在NS2仿真平台上进行了各种数据流环境下的仿真实验,结果表明该算法和RCP一样具有较高的网络利用率,并且拥有较低的队列长度和较短的平均流完成时间。因此该算法能够在较快的速度下反馈精确速率并具有较短的平均流完成时间,能提升网络的应用性能。(2)分析了无线网络中TCP拥塞控制的现状和限制,在具有高错误率的无线环境下,AMID拥塞控制方案的吞吐量会急剧下降。发现其主要原因是传统的TCP拥塞控制机制不能够区分数据包丢失的原因,即是由无线信道造成的还是有网络拥塞造成的丢包,因此在实际网络并没有发生拥塞,但是由于无线信道错误造成无码丢包的情况下,TCP依旧降低其发送速率。现有的基于端到端的带宽估计拥塞控制方案,都有TCP拥塞控制协议遗留下来的缺点,比如在无线链路下性能较低、产生丢包时吞吐量抖动过大、带宽利用率不高等。本文提出一种基于带宽估计的速率反馈拥塞控制方案,并设计一种带宽估计方法,将基于RCP协议的精确速率反馈拥塞控制算法应用到无线网络中,最后根据NS2仿真实验分析,可以获得较高的吞吐量和稳定性。(3)对多路径传输控制协议进行了分析,发现保证多条路径同时进行可靠传输十分重要,同时,对MPTCP的拥塞控制机制进行讨论,用速率反馈代替基于窗口的MPTCP协议,提出一种基于速率的MPTCP拥塞控制方案,将精确速率反馈拥塞控制协议应用到MPTCP的每条子流的拥塞控制中,充分提高每条子流的吞吐量,并通过分析,理论上该方案能够快速利用剩余带宽,拥有较快的收敛速度和较高的吞吐量。
[Abstract]:With the rapid development of network technology, the Internet has become an indispensable part of people's life. With the development of network bandwidth network hardware technology continues to increase, but the cyber source is limited, due to the distribution of resources and traffic in the network is not uniform, the occurrence of network congestion has become the inherent attributes of the Internet. In order to increase the utilization rate of the Internet the bandwidth, improve the stability of the Internet, need to perform congestion control. According to the congestion control algorithm running position, can be divided into source algorithm and link algorithm source. The algorithm only involves the network edge equipment, according to the information data transmission rate adjustment of the network edge equipment acquisition, such as is the use of network host access to the congestion control mechanism of TCP information to predict the occurrence of network congestion; link algorithm congestion information collection network equipment through the data of Baotou, this letter Write information packets, and congestion information feedback to the host to detect congestion, such as the explicit congestion control algorithm. The traditional congestion control mechanisms are often improved by TCP and TCP to implement the agreement, with the development of Internet technology, this system has exposed many limitations. The basic principle of the analysis of the current TCP congestion control the mechanism, including slow start, congestion avoidance, fast recovery and fast retransmit mechanism, and some of the TCP congestion control protocol, such as TCP Westwood, TCP Vegas, HSTCP TCP, found the window decrease performance in high-speed network and wireless network is greatly reduced because of being unable to make use of bandwidth of the channel error rate. To solve these problems, through the analysis of the explicit congestion control mechanism, this paper based on RCP (Rate Control Protocol) feedback congestion control based on the accurate rate, and according to the wireless network is put forward A bandwidth estimation rate feedback based congestion control scheme, finally proposed a congestion control scheme based on MPTCP. The specific contents are as follows. (1) in-depth analysis of RCP congestion control, the use of the link capacity in previous time rate to estimate the current flow quantity, under the estimation method must limit the number of data streams flow more and larger changes in a short scene data, the RCP protocol will be due to the calculation of the number of data streams through the router large deviation, caused by inaccurate rate feedback. Aiming at this problem, this paper proposed a feedback congestion control algorithm accuracy rate based on the RCP protocol, the algorithm the number is estimated by omitting the router's flow, can accurately calculate the feedback rate, and the simulation experiments of various data flow environment on NS2 simulation platform, the results show that the The utilization rate of algorithm and RCP had higher network, and has a lower queue length and shorter average flow time. So this algorithm can accurately in high speed feedback rate and has shorter average flow time, application performance can improve the network. (2) analyzed the status quo and limitation TCP congestion control in wireless networks, the wireless environment has high error rate, AMID congestion control scheme, the throughput will drop sharply. The main reason is that traditional TCP congestion control mechanism is not able to distinguish the cause of packet loss, which is caused by the wireless channel or packet loss caused by network congestion, so in the actual network and no congestion occurs, but due to wireless channel errors caused by no code in the case of packet loss, TCP still reduces its sending rate. Based on the existing end-to-end bandwidth estimation of congestion control. The case has left TCP congestion control protocol shortcomings, such as performance in wireless link under low packet throughput jitter generation is too large, the bandwidth utilization rate is not high. This paper presents a bandwidth estimation feedback rate based congestion control scheme, and design a method to estimate the accurate rate of bandwidth, RCP protocol feedback congestion control algorithm is applied to the wireless network based on NS2, according to the analysis of simulation experiment, we can obtain higher throughput and stability. (3) of multi path transmission control protocol was analyzed, found that many routes and reliable transmission is very important, at the same time, the MPTCP congestion control mechanisms are discussed, with the rate feedback instead of windows based on MPTCP protocol, we propose a MPTCP congestion control scheme based on the accurate rate feedback congestion control protocol applied to each MPTCP flow. In stopper control, we can improve the throughput of each sub stream, and theoretically, the scheme can quickly utilize the remaining bandwidth and have faster convergence speed and higher throughput.

【学位授予单位】：宁波大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TP393.06

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