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针对有线网络中的拥塞控制机制ECN进行改进,引入网络负荷因子的概念来更准确、有效的更新发送方的窗口大小,并将它和无线网络中的WELN机制相结合,提出了ECLN机制来提高在混合网络下的网络性能,并用NS2仿真工具在物理层引入无线信道错误模型来模拟无线链路上的丢包现象.仿真结果表明,该算法能够有效降低丢包数,明显提高网络的吞吐量. 相似文献
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提出了一种新的自适应分层多播拥塞控制方案(ALM)。ALM是发送方与接收方共同驱动、由路由器辅助流量控制的拥塞控制方案,通过把发送方的动态分层和接收方的自适应速率调整有机结合,不仅增强了分层多播的适应能力,提高了系统的吞吐量,而且较好地满足了TCP友好性。仿真实验表明,ALM能有效地利用网络带宽,解决网络带宽的异构性问题,并能通过接收端计算TCP友好速率,使接收端达到与TCP流公平竞争网络资源的目的。 相似文献
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Chi Zhang Lefteris Mamatas Vassilis Tsaoussidis 《International Journal of Communication Systems》2009,22(5):513-530
While there exist extensive research works on congestion control and active queue management, or the joint dynamics of a congestion control strategy with the random early detection (RED) algorithm, little has been done on the interactions between different window adjustment strategies and different queue management schemes such as DropTail and RED. In this paper, we consider a spectrum of TCP‐friendly additive increase and multiplicative decrease (AIMD) parameters. At the one end of this spectrum, smooth‐TCP enhances smoothness for multimedia applications by reducing the window decrease ratio upon congestion, at the cost of the additive increase speed and the responsiveness to available bandwidth. At the other end, responsive‐TCP enhances the responsiveness by increasing the additive increase speed, at the cost of smoothness. We investigate the network dynamics with various combinations of AIMD parameters and queue management schemes, under different metrics. The investigation is conducted from the deployment (especially incremental deployment) point of view. We discussed the impact of the interactions on the goodput, fairness, end‐to‐end delay, and its implications to energy consumption on mobile hosts. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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随着网络的快速发展,网络带宽的不断增加,适用于高速长距离网络的TCP协议不断涌现.就近几年提出的几个具有代表性的高速TCP进行了性能比较,尤其对它们的链路利用率和公平性进行了分析.通过分析和比较,获得了很多有用的结论,为TCP的研究进一步指明了方向. 相似文献
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Hualiang Chen Zhongxin Liu Zengqiang Chen Zhuzhi Yuan 《International Journal of Communication Systems》2006,19(7):831-844
PGM congestion control (pgmcc), a single‐rate multicast congestion control scheme, is one of the most promising schemes which aim to solve the problem of multicast fairness with TCP. However, by deep investigation, we find that there exist two inappropriate mechanisms in this scheme, which are the fixed slow start threshold (ssthresh) and the mechanism of changing a group representative (acker). Our experiments have revealed the fact that these mechanisms can lead to the unfairness of pgmcc under some network conditions. In this paper, two new mechanisms have been proposed to replace the original ones. One mechanism is to make the sender adapt the value of ssthresh to the network conditions to mimic the action of TCP, and in order to avoid being more aggressive than TCP, the other one is to make the sender reduce the congestion window by half when the acker changes. Our experiment results, parts of which are discussed in this paper, show that the modified pgmcc can achieve better performance than the original one. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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To solve the problem that most of existing layered multicast protocols cannot adapt todynamic network conditions because their layers are coarsely granulated and static,a new congestioncontrol mechanism for dynamic adaptive layered multicast(DALM) is presented.In this mechanism,anovel feedback aggregating algorithm is put forward,which can dynamically determine the number oflayers and the rate of each layer,and can efficiently improve network bandwidth utilization ratio.Additionally,because all layers is transmitted in only one group,the intricate and time-consuminginternet group management protocol(IGMP) operations,caused by receiver joining a new layer orleaving the topmost subscribed layer,are thoroughly eliminated.And this mechanism also avoids otherproblems resulted from multiple groups.Simulation results show that DALM is adaptive and TCPfriendly. 相似文献
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周屹然 《电信工程技术与标准化》2004,(9):87-90
TCP友好的速率控制(TFRC)主要适用于实时数据传输的一种拥塞控制机制,具有突出的TCP友好性即在相同的环回时间(RTT)下可以和TCP流享有近乎相同的带宽,从而避免了由于UDP等传输层协议缺乏拥塞控制而带来的网络拥塞甚至崩溃.本文简要介绍了它的协议机制并通过一些仿真和试验的结果初步讨论了其性能. 相似文献
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TCP Vegas exhibits unfair congestion avoidance mechanism, which aggravates when there are insufficient network resources to accommodate buffer space of a pipe (bandwidth delay product). To remedy this shortcoming, we propose an Enhanced VegAs (EVA) that employs three auxiliary mechanisms: Δ revision, congestion detection and congestion tendency detection. A 2k factorial design with replications is used to study the effect of the three mechanisms. Our results show that TCP EVA achieves better performance than Vegas under various network conditions. Furthermore, congestion avoidance schemes, such as TCP EVA, perform much better than congestion control schemes, such as TCP Reno, in resource‐insufficient networks. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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Sungwon Yi Martin Kappes Sachin Garg Xidong Deng George Kesidis Chita R. Das 《Wireless Communications and Mobile Computing》2008,8(4):421-434
Wireless access points (APs) act as bridges between wired and wireless networks. Since the actually available bandwidth in wireless networks is much smaller than the bandwidth in wired networks, there is a disparity in channel capacity which makes the access point a significant network congestion point in the downstream direction. A current architectural trend in wireless local area networks (WLAN) is to move functionality from APs to a centralized gateway in order to reduce cost and improve features. In this paper, we study the use of RED, a well known active queue management (AQM) scheme, and explicit congestion notification (ECN) to handle bandwidth disparity between the wired and the wireless interface of an access point. Then, we propose the Proxy‐RED scheme, as a solution for reducing the AQM overhead from the access point. Simulations‐based performance analysis indicates that the proposed Proxy‐RED scheme improves the overall performance of a network. In particular, the Proxy‐RED scheme significantly reduces packet loss rate and improves goodput for a small buffer, and minimizes delay for a large buffer size. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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随着各种网络应用的不断涌现,网络拥塞问题变得越来越严重,解决这一问题也就越来越重要。阐述了TCP拥塞控制的基本原理,然后介绍了现有的几种TCP拥塞控制算法,并对这些算法进行了分析比较,结果表明虽然每种算法都有其优点,但也存在不足,不能从根本上解决拥塞问题。文章最后指出了拥塞控制的问题所在以及解决方法的发展趋势。 相似文献
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In this paper, we design and evaluate an Internet friendly transport‐level protocol (IFTP) for solving the TCP‐friendly problem. IFTP has two modes of operation. In the standard mode, the IFTP connection faithfully emulates the behaviour of TCP in order to roughly obtain a bandwidth equal to that of a TCP connection. In the extended mode, a simple modification is used to grant QoS‐differentiated services to selected connections. Connections running in the extended mode can get enhanced bandwidth while still emulating the general behaviour of TCP. We develop an analytical model for the congestion control mechanism of IFTP. We also derive analytically the amount of bandwidth that IFTP may be able to claim from TCP in ideal and non‐ideal environments. We evaluate IFTP through simulation and prove its TCP friendliness as well as provide performance results on some of the important metrics such as packet delay, delay jitter, packet loss and link utilization. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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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. 相似文献
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文章主要研究了TCP/IP中主要采用的拥塞控制算法,讨论了目前TCP/IP中常用的AIMD算法的稳定性、收敛性、公平性,及其约束条件,并进一步将MAIMD算法和AIMD算法进行了比较。最后仿真了两用户不同RTT时的状态轨迹和公平指数轨迹。 相似文献
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With the rapid growth of rate-based services and wireless applications,improving Transmission Control Protocol (TCP) congestion control has been becoming more important in the network research field. This paper first briefly introduces the Additive-Increase Multiplicative-Decrease (AIMD) (a,b) algorithm,and then presents an improved TCP congestion control mechanism (D-AIMD) whose principles and simulation results are discussed in detail. This mechanism can be easily implemented with lower additional overheads and can efficiently improve network performance. 相似文献
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James Aweya Michel Ouellette Delfin Y. Montuno 《International Journal of Communication Systems》2002,15(10):907-920
In explicit TCP rate control, the receiver's advertised window size in acknowledgment (ACK) packets can be modified by intermediate network elements to reflect network congestion conditions. The TCP receiver's advertised window (i.e. the receive buffer of a TCP connection) limits the maximum window and consequently the throughput that can be achieved by the sender. Appropriate reduction of the advertised window can control the number of packets allowed to be sent from a TCP source. This paper evaluates the performance of a TCP rate control scheme in which the receiver's advertised window size in ACK packets are modified in a network node in order to match the generated load to the assigned bandwidth in the node. Using simulation and performance metrics such as the packet loss rates and the cumulative number of TCP timeouts, we examine the service improvement provided by the TCP rate control scheme to the users. The modified advertised windows computed in the network elements and the link utilization are also examined. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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LIU Gang ZHANG De-yun LIU Jing DING Hui-ning School of Electronics Information Engineering Xi'an Jiaotong University Xi'an P.R. China School of Computer Science Engineering Xi'an University of Technology Xi'an P.R. China Northwest Regional Network of CERNET Xi'an Jiaotong University Xi'an P.R. China. 《中国邮电高校学报(英文版)》2004,11(2)
1 Introduction TransmissionControlProtocol(TCP) [1 ] iswidelyusedinthecurrentInternet,andmanyofpopularInternetservices,includingHyperTextTransferProtocol (HTTP) [2～3] andFileTransferProtocol(FTP) [4] ,useitasthede factostandardtransport layer protocol.TCPVegas[5～6] wasproposedin1 994,whichovercameseveraldrawbacksofTCPReno[7] ,andcanachievebetween 40and 70 percentbetterthroughputascomparedtotheimplementa tionofTCPintheRenodistributionofBSDU NIX[8] andotherTCPversion[9～1 1 ]… 相似文献