TCP拥塞控制机制浅析

TCP是当今网络中主要的传输协议,它采用了慢启动、拥塞避免、快速重传、快速恢复四种算法,能满足IP网络中数据的可靠传输。但是当出现多个数据包丢失时,由于TCP采用了累计确认机制,造成系统吞吐量下降。文章介绍了一种SACK拥塞控制机制,与传统的Tahoe、Reno对比,并通过仿真实验说明了SACK是一种最好的TCP恢复机制。     

无线网络中一种改进的TCP拥塞控制机制

由于无线网络中存在高误码、信号衰落、切换等原因，使传统TCP的应用受到了挑战。本文提出了一种新的无线网络拥塞控制方案—MRBR算法，它根据RTT值的变化对Reno协议进行修改，区分网络拥塞和无线链路差错，然后针对不同的原因，选取正确的参数实施拥塞控制。MRBR算法只需修改协议的发送部分，并且可以与Reno兼容。仿真结果表明，该方法增强了网络对拥塞以及随机差错的判断处理能力，有效提高了网络的吞吐量。     

几种TCP协议下F、G函数的研究

随着网络技术的不断提高,一些新型的高速网络投入使用,产生了一系列如TCP拥塞控制算法,其中Reno协议、Vegas协议、RED协议以不同的方式解决了网络拥塞的问题。通过在以上3种协议模型下对F、G函数进行推导,用对偶方程求解的方法,比较3种协议的优劣,为网络模型的建立打下基础。     

TCP拥塞控制技术研究

TCP拥塞控制机制对Internet的稳定运行起着重要作用.针对三种典型的TCP拥塞控制算法--Tahoe、Reno和Vegas的性能作出分析,Tahoe和Reno是目前TCP拥塞控制中最常用的;Vegas是在对Reno的发送端算法进行修改的基础上提出的一种拥塞控制算法.最后,对这些算法做了详细的比较和总结,并指出了进一步改进TCP拥塞控制的必要性.     

TCP/IP网络的拥塞控制综述

分析网络拥塞的产生原因,并对拥塞控制进行归纳、分类;通过对原理的分析和性能的比较,详细探讨两种主要的端到端的拥塞控制算法Reno和Vegas,结合对网络层的拥塞控制算法的分析,讨论了TCP拥塞控制研究的发展趋势。     

流量/拥塞控制技术研究

流量/拥塞控制的基本目的是以分布处理的方式有效地控制结点间的数据流,从而避免网络中出现拥塞。拥塞控制相应的控制策略称为拥塞控制算法(协议)。简述了Internet上基于TCP/IP的拥塞控制机制,分析和比较了TCP/IP上具体实现算法的稳定性,讨论了TCP/IP拥塞控制所面临的问题。     

TCP协议中的拥塞控制

网络的拥塞会导致吞吐量的下降 ,降低网络的效率 ,对网络的正常运转有很大的影响 ,最终可能导致网络的崩溃。分析了在Internet上TCP IP协议拥塞控制的原理 ,提出了在TCP层抑制拥塞的策略、方法 ,并提出了今后的研究方向     

TCP/IP协议的拥塞控制策略

网络拥塞问题会导致网络性能下降,对网络正常运行有很大影响,严重时会导致死锁的产生.文中分析了网络拥塞的产生的原因,并着重讨论了传统端到端的TCP拥塞控制的策略和方法,传统TCP拥塞控制策略提出了改进策略和网络层的IP拥塞控制策略.最后对基于TCP和IP拥塞控制策略进行了对比探讨.     

基于DSP和TCP/IP的嵌入式网络数据采集系统

提出一种有效的、低成本的嵌入式系统TCP/IP协议栈实现方案.阐述了在TMS320F2407A中实现TCP/IP协议的基本原理.通过对TCP/IP协议进行裁减,采用全汇编语言程序设计方法、灵活的消息控制机制和缓冲区管理,在有限的代码空间内实现了TCP/IP协议栈.     

基于带宽测量技术的TCP拥塞窗口在线学习方法

为了改进传输层协议提高吞吐量,本文提出了一种基于ACK时间间隔的在线学习方法（TCP-Learning）,该方法采用可用带宽测量技术,快速学习网络链路中可用剩余带宽并能够迅速调整TCP拥塞窗口。仿真结果表明,在链路处于良好状态下,TCP-Learning吞吐量略优于Reno和Vegas等传统拥塞控制算法,但在链路较差情况下,TCP-Learning吞吐量明显优于Reno和Vegas等传统拥塞控制算法。     

TCP拥塞控制技术初探

首先探讨了网络拥塞出现的原因,然后分析了TCP拥塞控制的原理及四个TCP拥塞控制算法的性能,接着着重论述了TCP拥塞控制所面临的问题和对应算法的改进,最后提出了其进一步的研究方向。     

TCP Veno: TCP enhancement for transmission over wireless access networks

Wireless access networks in the form of wireless local area networks, home networks, and cellular networks are becoming an integral part of the Internet. Unlike wired networks, random packet loss due to bit errors is not negligible in wireless networks, and this causes significant performance degradation of transmission control protocol (TCP). We propose and study a novel end-to-end congestion control mechanism called TCP Veno that is simple and effective for dealing with random packet loss. A key ingredient of Veno is that it monitors the network congestion level and uses that information to decide whether packet losses are likely to be due to congestion or random bit errors. Specifically: (1) it refines the multiplicative decrease algorithm of TCP Reno-the most widely deployed TCP version in practice-by adjusting the slow-start threshold according to the perceived network congestion level rather than a fixed drop factor and (2) it refines the linear increase algorithm so that the connection can stay longer in an operating region in which the network bandwidth is fully utilized. Based on extensive network testbed experiments and live Internet measurements, we show that Veno can achieve significant throughput improvements without adversely affecting other concurrent TCP connections, including other concurrent Reno connections. In typical wireless access networks with 1% random packet loss rate, throughput improvement of up to 80% can be demonstrated. A salient feature of Veno is that it modifies only the sender-side protocol of Reno without changing the receiver-side protocol stack.     

Equilibrium and Fairness of Networks Shared by TCP Reno and Vegas/FAST

It has been proved theoretically that a network with heterogeneous congestion control algorithms that react to different congestion signals can have multiple equilibrium points. In this paper, we demonstrate this experimentally using TCP Reno and Vegas/FAST. We also show that any desired inter-protocol fairness is in principle achievable by an appropriate choice of Vegas/FAST parameter, and that intra-protocol fairness among flows within each protocol is unaffected by the presence of the other protocol except for a reduction in effective link capacities. Dummynet experiments and ns-2 simulations are presented to verify these results.     

TFRC friendliness and the case of ECN

The TFRC protocol has been proposed as a TCP‐friendly protocol to transport streaming media over the Internet. However, its deployment is still questionable because it has not been compared to other important protocols, analysed in the presence of important mechanisms, such as the explicit congestion notification (ECN), and studied under more realistic network conditions. In this paper, we address these three aspects, including other congestion control protocols not considered before in the same investigation, such as TCP Tahoe, Reno, Newreno, Vegas, Sack, GAIMD, and the Binomial algorithms, the effect of using ECN in the friendliness of the protocols, and the fairness of the protocols under static and dynamic network conditions. We found that TFRC can be safely deployed in the Internet if competing with TCP Tahoe, New Reno and SACK since fairness is achieved under all scenarios considered. We also found that ECN actually helps in achieving better fairness. However, fairness problems arise when TFRC competes with TCP Reno, GAIMD, SQRT or IIAD in static or dynamic conditions, or both. We used normalized throughput, fairness index, and convergence time as the main performance metrics for comparison. Copyright © 2004 John Wiley & Sons, Ltd.     

前向主动网络拥塞控制算法及其性能分析

本文提出了一种基于主动式网络(Active Networks)技术的拥塞控制算法FACC(Forward Active Networks Congestion Control).与传统的TCP(Transport Control Protocol)相比,FACC算法通过在网络结点直接提供拥塞检测和拥塞控制机制,大大缩短源端点的拥塞反应时间,从本质上提高了网络拥塞检测和控制的性能,从而提高了终端用户的平均吞吐量.文中还利用计算机仿真研究了FACC算法在各种网络条件下的性能,并与传统的Tahoe,Reno,NewReno及SACK TCP协议做了对比.结果表明无论网络中存不存在非受控数据流时,FACC控制算法均能明显地提高用户终端的平均吞吐量,并且由于采用FACC控制算法而增加的网络结点运算迟延也很小.     

基于TCP/IP的卫星通信传输链路的改进

卫星网络固有的一些特性影响了TCP／IP的性能。针对延迟、拥塞率、比特差错率、网络不对称性等问题,提出了支持较大的流量控制窗口及改进拥塞控制算法的方法,对现有的TCP／IP进行了改进。     

TCP/IP网络的动态模型描述

拥塞现象成为TCP/IP网络发展面临的一个重要问题。因此，拥塞控制对TCP/IP网络的鲁棒性和稳定性具有重要作用。目前，网络拥塞控制策略主要包括两类：端到端的控制机制，如TCP拥塞控制算法；网络内部的主动队列管理(AQM)策略。但由于缺乏对网络系统动态特性的了解，这些拥塞控制策略大都基于专家经验，并没有建立完整的理论分析框架。为此，本文从数据流的角度出发，通过建立网络基本单元状态方程模型来实现IP网络系统的数学解析模型，然后用混杂系统来描述TCP带有拥塞控制策略的数据传输过程，建立了TCP/IP网络的动态模型，为网络系统中动态性能的分析、拥塞控制策略的设计奠定了基础。实验结果表明，该数学模型与NS仿真实验的结果相一致。