城域以太网中基于抖动检测的拥塞控制算法

提出了一种在城域以太网节点设备中基于抖动检测的拥塞控制算法(JDCC算法).通过检测和丢弃那些时延抖动值超过用户容忍门限值的数据分组,给正常的数据分组提供了更高的带宽,提高了实时多媒体流在城域以太网中传输的服务质量.实验结果表明JDCC算法可以更有效地降低实时多媒体流的平均时延抖动,且能提高有效吞吐量.     

基于丢包和网络测量的TCP拥塞控制算法研究综述

拥塞控制一直是网络通信领域的重要研究课题,它可以避免因网络拥塞而导致的传输质量严重下降,同时确保网络带宽的高效利用。TCP在互联网的发展过程中扮演着不可或缺的重要的角色,是实现网络拥塞控制的重要途径。随着互联网技术的发展,提出了多种TCP拥塞控制算法,其中基于丢包和网络测量两类算法最为典型。文章梳理了TCP拥塞控制算法的发展历程,并详细分析了基于丢包和基于网络测量两类算法的原理及优缺点。     

一种基于多径负载均衡的无线互联网TCP拥塞控制策略

针对无线互联网中拥塞控制存在的问题,提出了一种支持多径负载均衡技术的TCP拥塞控制策略。该篆略主要包括拥塞检测和拥塞控制两个部分。其中基于带宽估计的拥塞检测方法,能有效区分差错丢包和拥塞丢包;在检测到拥塞发生后,采用基于多径负载均衡技术的拥塞控制策略,并使用基于时延估计的多径分组分配策略,在缓解拥塞的同时避免了多路通信的包乱序问题,有效的提高吞吐量,减小端到端时延。     

一种基于QoS的空间延迟/中断容忍网络拥塞控制方法

为缓解网络拥塞对空间延迟/中断容忍网络产生的影响,该文提出一种基于QoS的网络拥塞控制算法。该算法包括接触拥塞判断和基于QoS的数据转发两种机制,分别从接触剩余可用容量和节点剩余存储空间两方面对每一段接触的拥塞程度进行预测,将接触划分为不同的拥塞等级。在计算路由时,以整段路径中所包含接触的最高拥塞等级为该路径的拥塞等级,并根据该拥塞等级发送不同优先级的数据。实验表明,基于QoS的拥塞控制算法可以提高低优先级数据的传递率并在节点存储空间不足时降低最高优先级数据的传递时延。     

基于实测流量的网际分组丢失率分析

分组丢失率是评价网络性能的一个重要指标。提出了一种利用完整TCP流计算实测数据中分组丢失率的方法,并基于实测数据对CERNET江苏省网与外部不同网络分区的分组丢失率进行分析。算法给出了基于实测数据的分组丢失率包括首次分组丢失率pfl、整体分组丢失率psl和重传率prp 3个测度。统计分析表明,在绝大多数情况下,pfl比psl小,而prp比pfl和psl明显要高,验证了分组丢失对网络性能的影响以及重传率明显比分组丢失率高。     

基于线性回归的卫星数据传输TCP拥塞控制研究

针对当前卫星数据地面传输环境遇到的诸如TCP传输时延长、误码率高、带宽不对称等和网络拥塞密切相关的问题,文中从拥塞控制的角度出发,在基于往返时延的拥塞控制算法Vegas基础上,加入对往返时延(RTT)的动态控制机制,以此为突破点对整个卫星数据地面传输的网络资源进行优化和调整,提高网络资源利用率。实现对往返时延(RTT)动态调整的方法是对已得到的往返时延数据进行线性回归分析,通过不断地线性回归优化对数据进行拟合得到基于预测的往返时延算法Lr Vegas。     

基于ECN跨层机制的无线TCP性能改进方案

针对无线环境下TCP（传输控制协议）调用拥塞控制算法致使性能下降的问题,提出一种基于ECN（显式拥塞通知）跨层机制的无线TCP改进方法。算法在ECN机制上判断网络是否拥塞以及丢包发生时具体丢包类型。并在此基础上针对网络具体状况采取不同的拥塞窗口控制机制,更精确的网络信息有效提高了数据发送的可靠性。仿真结果表明该算法可提...     

基于模糊逻辑的无线网络流量自适应控制

文章在分析现有提高无线TCP性能方案的基础上，提出一种新的流量控制方法，即基于显式窗口反馈的无线网络流量控制方案。在Snoop中引入有线网络的显示窗口自适应（EWA）算法，通过对BS共享缓存的实时监测，应用模糊控制算法预测当前拥塞窗口（cwnd）的大小，并显式反馈给发送端，使TCP的发送窗口能快速响应网络负荷状况的变化．避免分组的丢失。仿真结果表明．该方法增强了网络对拥塞的自适应性以及对无线信道差错的实时处理能力．提高了网络的吞吐量。     

HSDPA网络中基于虚拟队列的Iub流量控制

随着UMTSHSPA+技术的发展以及上下行峰值速率的不断增加,无线接入网络拥塞日益严重。由于底层重传协议的存在,TCP的拥塞控制方法不能有效解决HSDPA网络中的拥塞问题。3GPP定义了HSDPA流量控制算法,但该算法仅解决了空中接口的拥塞问题。本文提出了基于虚拟队列的流量控制方法,旨在解决Iub传输网络的拥塞问题。系统分析和性能仿真证明了该算法能有效地规避网络拥塞导致的RLC实体重传,从而提高Iub传输链路的吞吐量,并且传输时延和丢包的情况也不会恶化。此外,该算法可以针对运营商的具体服务质量(QoS)需求进行调节。     

基于无线传感器网络的跨层拥塞控制协议

无线传感器网络(WSN)中由拥塞引起的大量分组重传以及重传多次失败后的分组丢弃会导致较长的时延、较高的分组丢失率和较多的能量消耗.为了准确探测和控制网络拥塞,提出了一种基于跨层设计的拥塞控制协议,即上行拥塞控制(UCC)协议.该协议利用节点在媒质接人控制(MAC)层中未占用的缓冲器区间大小和所预测的通信流量作为该节点的...     

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.     

Rate Control Algorithm Considering Mobility in Mobile Ad Hoc Networks

For reducing the loss of data packet due to network congestion and mobility, rate control algorithm is effective means for ensuring the fair allocation of network resource among communication flows and alleviating network congestion. The Transport Control Protocol (TCP) was originally designed for wire-line networks, where the links are assumed to be reliable and with fixed capacities. However, the performance of TCP becomes very poor when it is directly used in ad hoc networks. Some optimization-based congestion control schemes have been proposed to improve TCP performance in ad hoc networks, but the mobility of hosts and route change frequently are not considered for designing rate control algorithm. In this paper, we propose rate control algorithms in a more practical way by taking into account link congestion and node movement. Numerical results show that the rate control algorithms can approach the globally optimal value and show the effect of the node mobility on the algorithms.     

无线网络中TCP拥塞控制算法的性能分析

根据无线网络中存在随机数据包丢失的特定情况,对TCP拥塞控制算法在无线网络中的性能进行了分析。理论分析和仿真结果表明,随着无线链路中随机数据包丢失概率的增加,TCP拥塞控制算法将导致无线网络性能的严重下降。     

Enhancement of TCP over wired/wireless networks with packet loss classifiers inferred by supervised learning

TCP is suboptimal in heterogeneous wired/wireless networks because it reacts in the same way to losses due to congestion and losses due to link errors. In this paper, we propose to improve TCP performance in wired/wireless networks by endowing it with a classifier that can distinguish packet loss causes. In contrast to other proposals we do not change TCP’s congestion control nor TCP’s error recovery. A packet loss whose cause is classified as link error will simply be ignored by TCP’s congestion control and recovered as usual, while a packet loss classified as congestion loss will trigger both mechanisms as usual. To build our classification algorithm, a database of pre-classified losses is gathered by simulating a large set of random network conditions, and classification models are automatically built from this database by using supervised learning methods. Several learning algorithms are compared for this task. Our simulations of different scenarios show that adding such a classifier to TCP can improve the throughput of TCP substantially in wired/wireless networks without compromizing TCP-friendliness in both wired and wireless environments.     

TCP-DCR: a novel protocol for tolerating wireless channel errors

This paper presents TCP-DCR, a set of simple modifications to the TCP protocol to improve its robustness to channel errors in wireless networks. TCP-DCR is based on the simple idea of allowing the link-level mechanism to recover the packets lost, due to channel errors, thereby limiting the response of the transport protocol to mostly congestion losses. This is done by delaying the triggering of congestion response algorithms for a small bounded period of time /spl tau/ to allow the link-level retransmissions to recover the loss due to channel errors. If at the end of the delay /spl tau/ the packet is not recovered, then it is treated as a packet lost due to congestion. We analyze TCP-DCR to show that the delay in congestion response does not impact the fairness towards the native implementations of TCP that respond to congestion immediately after receiving three dupacks. We evaluate TCP-DCR through simulations to show that it offers significantly better performance when channel errors contribute more towards packet losses in the network with no or minimal impact on the performance when congestion is the primary cause for packet loss. We also present an analysis to show that the number of flows in the network significantly influences protocol evaluation in the wireless networks.     

多个TCP连接的拥塞丢包模型

本文提出了有关TCP连接的拥塞丢包分析模型.网络瓶颈一般承载许多TCP连接,瓶颈处不可避免的拥塞和缓存溢出,是导致网上丢包的主要原因.网络瓶颈处的行为很大程度上左右了网络性能.本文的模型估计了存在大量持续TCP连接时,网络瓶颈的丢包概率和网络传输中断概率,给出了对实际网络的良好近似.这对于研究TCP对网络性能的影响,提出改善网络性能的新算法,以及分析(从长远来看)TCP还应做哪些改进,都是非常有用的.     

TCP-Jersey for wireless IP communications

Improving the performance of the transmission control protocol (TCP) in wireless Internet protocol (IP) communications has been an active research area. The performance degradation of TCP in wireless and wired-wireless hybrid networks is mainly due to its lack of the ability to differentiate the packet losses caused by network congestions from the losses caused by wireless link errors. In this paper, we propose a new TCP scheme, called TCP-Jersey, which is capable of distinguishing the wireless packet losses from the congestion packet losses, and reacting accordingly. TCP-Jersey consists of two key components, the available bandwidth estimation (ABE) algorithm and the congestion warning (CW) router configuration. ABE is a TCP sender side addition that continuously estimates the bandwidth available to the connection and guides the sender to adjust its transmission rate when the network becomes congested. CW is a configuration of network routers such that routers alert end stations by marking all packets when there is a sign of an incipient congestion. The marking of packets by the CW configured routers helps the sender of the TCP connection to effectively differentiate packet losses caused by network congestion from those caused by wireless link errors. This paper describes the design of TCP-Jersey, and presents results from experiments using the NS-2 network simulator. Results from simulations show that in a congestion free network with 1% of random wireless packet loss rate, TCP-Jersey achieves 17% and 85% improvements in goodput over TCP-Westwood and TCP-Reno, respectively; in a congested network where TCP flow competes with VoIP flows, with 1% of random wireless packet loss rate, TCP-Jersey achieves 9% and 76% improvements in goodput over TCP-Westwood and TCP-Reno, respectively. Our experiments of multiple TCP flows show that TCP-Jersey maintains the fair and friendly behavior with respect to other TCP flows.     

一种支持多媒体通信QoS的拥塞控制机制

本文针对Internet传输协议TCP的和式增加积式减少(AIMD)拥塞控制机制不适应多媒体通信,而目前拥塞控制的研究又大多集中在尽量做好(Best-effort)服务上的问题,结合Internet上多媒体通信的特点及其对QoS的要求,提出了一种将多媒体通信服务质量(QoS)控制和基于速率拥塞控制结合起来的拥塞控制的新机制.本文详细地研究了这一机制,并提出了源端多媒体数据流的带宽控制策略、基于动态部分缓存共享(DPBS)的数据包丢失控制方案和接收端计算包丢失率p的方法.最后给出了整个拥塞控制机制的系统结构.     

A Novel Wireless TCP and its Steady State Throughput Model

1　Introduction　WiththegrowthofwirelessnetworksandtheInter net,thedatatransmissionserviceoverwirelessnet worksbecomesmoreattractive .InthecurrentInternet,TCPiswidelyusedinpopularapplicationslikeTelnet,FTP ,andHTTP .　TCPisareliableconnection oriented protocolthatimplementscongestioncontrolbymeansofaslidingwindowalgorithm .TCPTahoeandReno[1～ 2 ] ,whichmakeuseoftheSlowStart (SS)andCongestionAvoid ance (CA)algorithmstoadjustthewindowsize ,havegotmuchsuccessintheInternet.Inparticular…     

Congestion control for multimedia applications in the wireless internet

This paper provides a parallel review of two important issues for the next‐generation multimedia networking. Firstly, the emerging multimedia applications require a fresh approach to congestion control in the Internet. Currently, congestion control is performed by TCP; it is optimised for data traffic flows, which are inherently elastic. Audio and video traffic do not find the sudden rate fluctuations imposed by the TCP multiplicative‐decrease control algorithm optimal. The second important issue is the mobility support for multimedia applications. Wireless networks are characterized by a substantial packet loss due to the imperfection of the radio medium. This increased packet loss disturbs the foundation of TCP's loss‐based congestion control. This paper contributes to the ongoing discussion about the Internet congestion control by providing a parallel analysis of these two issues. The paper describes the main challenges, design guidelines, and existing proposals for the Internet congestion control, optimised for the multimedia traffic in the wireless network environment. Copyright © 2004 John Wiley & Sons, Ltd.