Low pass filter/over drop avoidance (LPF/ODA): an algorithm to improve the response time of RED gateways

The low pass filter (LPF) algorithm, which is used to calculate the average queue length in the random early detection (RED) algorithm, results in a poor response time when RED recovers from congestion. In this paper, we propose a new algorithm, called low pass filter/over drop avoidance (LPF/ODA), to improve the response time of RED. LPF/ODA is based on reducing the time required by RED to recover from long‐term congestion. Simulation results have been used to show that the proposed LPF/ODA algorithm significantly improves the response time, throughput and delay of RED gateways. Copyright © 2002 John Wiley & Sons, Ltd.     

基于平均队列长度和滞留时间的RED算法

在无线通信网络环境下，提出了一种改进的基于平均队列长度和滞留时间的RED算法。这种算法根据平均队列长度和滞留时间计算数据包的丢弃概率，比传统的单纯基于平均队列长度的RED算法相比较，能更有效地实现无线网络中的拥塞控制。     

RED gateway congestion control using median queue size estimates

This paper focuses on the queue size estimation problem in random early detection (RED) gateways. Queue size estimation plays a fundamental role in the congestion control dynamics of RED, as it determines gateways' awareness of network congestion, which in turn determines the packet dropping/marking decision. Conventional RED gateways use exponentially weighted moving averages (EWMA) to estimate the queue size. These infinite impulse response (IIR) filters require very small EWMA weights in order to effectively avoid nonlinear instabilities in RED and to filter out bursty increases in the queue size. While small EWMA weights enable gateways to accommodate transient congestion, they also lead to gateways' failure to closely track rapid queue size depletion and thus causes link under utilization. We investigate the use of simple nonlinear queue size estimators. In particular, we study the congestion control dynamics of a network where adaptive weighted median filters are used for queue size estimation by the gateways. Analytical results for the expected queue size in the steady state are derived. Under this new queue size estimation framework, design guidelines for the remaining RED parameters are provided. Simulation results show that the proposed algorithm provides greater network power, better prevention of global synchronization, and a fairer treatment to bursty traffic than the RED algorithm does.     

基于H∞控制理论的网络拥塞控制器的设计

针对具有多维性、非线性、动态性、不确定性等复杂特征的计算机网络系统,文章从控制理论出发,提出了一种基于H∞控制理论的主动队列管理（AQM）算法,文章着重分析RED算法。首先,建立了AQM／TCP拥塞控制的动态模型;其次,系统的渐进稳定由线性矩阵不等式（LMI）描述,并应用MATLAB的LMI工具箱求解H∞控制的一般线性时滞系统;然后将求解结果应用到RED中,从而得出了控制器。最后在NS2平台上进行了仿真实验,试验结果表明,该算法在解决系统不确定性引起的鲁棒性问题上是有效的。     

A fuzzy-logic control algorithm for active Queue Management in IP networks

Active Queue Management （AQM） is an active research area in the Internet community. Random Early Detection （RED） is a typical AQM algorithm, but it is known that it is difficult to configure its parameters and its average queue length is closely related to the load level. This paper proposes an effective fuzzy congestion control algorithm based on fuzzy logic which uses the predominance of fuzzy logic to deal with uncertain events. The main advantage of this new congestion control algorithm is that it discards the packet dropping mechanism of RED, and calculates packet loss according to a preconfigured fuzzy logic by using the queue length and the buffer usage ratio. Theoretical analysis and Network Simulator （NS） simulation results show that the proposed algorithm achieves more throughput and more stable queue length than traditional schemes. It really improves a router＇s ability in network congestion control in IP network.     

一种基于动态部分缓存共享机制的RED改进

提出了一种基于动态部分缓存共享机制的随机早期检测(RED)拥塞控制改进方案，并给出了算法实现，最后通过仿真进行了性能分析，验证其为区分服务的不同性能要求提供了拥塞控制功能。     

基于自相似业务流的Hurst加权随机早检测算法

Floyd提出的随机早丢弃（RED，random carly detection）是基于传统的泊松（Possion）模型，不适应网络流量普遍呈现自相似性的特点。基于此目的，提出了一种新的RED算法——Hurst加权随机早检测算法（HWRED，Hurst weighted random early detection）。新算法能够根据输入流量的自相似系数Hurst，调整RED算法参数。仿真结果表明，新算法提高了队列长度的稳定性，减少了丢包率、排队时延和排队抖动，提高了网络的链路利用率。     

FRED-fair random early detection algorithm for TCP over ATMnetworks

The authors present the FRED (fair random early detection) algorithm as a congestion control mechanism for TCP over ATM networks. The FRED algorithm enhances the RED gateway algorithm, by using the fact that TCP connections should be allocated buffer space in proportion to their bandwidth-delay products. Through simulation, the effectiveness of the proposed FRED algorithm is shown as compared with the drop-tail and the original RED algorithms     

随机早期检测算法的参数研究

RED算法较好解决了TCP拥塞控制中延迟和长期拥塞问题,但RED算法对参数的设置很敏感,不同的参数设置对RED的性能影响很大。文章就参数的设置提高了RED算法的性能,克服它的一些缺点进行了探讨和研究。     

主动队列管理机制在无线系统中的优化

主动队列管理(AQM)是对抗拥塞的重要手段,其经典算法之一是随机早期丢弃,简称RED。为使其能适应无线传输高突发误帧的特点,本文提出了一种基于平均队列长度和平均包到达速率的改进RED算法,分析了其相对于传统RED算法在预防和处理拥塞时的优势。同时针对无线信道的时变特性,提出自适应MIR速率调整,以提高频谱利用率和进一步降低拥塞概率,并讨论了其对于系统性能的改善。     

无线Mesh网络中基于链路负载估算的拥塞控制策略

针对无线Mesh网络的网络特性,提出了一种基于链路负载估算的拥塞控制策略LLECC。LLECC算法计算有效链路带宽和链路负载估算确定RED算法中的调整因子,通过调整因子调整RED算法中的参数从而实现动态的对无线网络拥塞控制。详细讨论了LLECC算法的实现过程和相关参数的计算方法,通过仿真分析验证了该算法对无线Mesh网络性能的提高。     

串联排队RED、ERED网络分析模型

基于串联排队网络理论,建立了包括多个网络节点的串联排队RED和ERED分析模型。推导了具有指数分布分组丢失函数的RED算法(ERED)。在概率生成函数域,推导了节点的离去过程,并将其拟合为后续节点的到达过程,从而,刻画了多节点级联拥塞控制的通信场景。通过求解串联排队系统,得出串联排队RED、ERED以及DT 3种AQM机制的网络性能指标,分析了AQM参数设置对其性能的影响。针对不同突发度的业务源,给出每个节点和系统端到端性能指标。     

动态权重RED网关

随着网络流量的增加,拥塞控制的重要性日益突出,尤其是链路拥塞控制。IETF推荐RED(Random Early Detection)作为下一代Internet路由器的拥塞控制算法。该文在分析了RED的优点和缺点后,在现在RED算法的基础上通过改进RED算法的平均队列长度计算,使用平均队列长度的均值,判断拥塞的发生和结束,动态调整权重,提高RED对拥塞发生和拥塞结束的反应速度,缩短拥塞时间,维持较低的实际队列长度。最后用仿真验证了该方法。     

Design of Active Queue Management System for Scalable TCP in High Speed Networks

The Scalable Transmission Control Protocol (TCP), based on a multiplicative increase, multiplicative decrease congestion avoidance algorithm, has been proposed recently to overcome the inability of Standard TCP to utilize the full bandwidth in high speed networks. This paper employs a novel approach to derive a transfer-function model of Scalable TCP that is then employed in a control-theoretic design of random early detection (RED)-based active queue management (AQM) for such a network. Robust stability of the proposed scheme is established under prescribed conditions, and the design is validated by discrete-event simulations using the ns2 tool. This work was supported by a Gledden Visiting Senior Fellowship for the first author.     

确保最小发送速率的TCP友好拥塞控制算法

提出一种确保最小发送速率的TCP友好拥塞控制算法CQTCCA(certified quality TCP-friendly congestion control algorithm)。该算法通过将网络结点和端点相结合，在端点对UDP数据流采用基于公式的发送速率调整，使之体现对TCP数据流的友好性；在结点对RED进行改造，得到提供带优先级包标记的MRED算法，保证对实时多媒体数据流的最小带宽要求。仿真实验验证了本算法有效性。     

A stochastic dynamic controller for random early detection queues using a Kalman filter algorithm

The stabilizing random early detection (RED) congestion control algorithm in transmission control protocol (TCP)/IP networks is a control theory problem. Significant attention has been drawn to this problem in the networking and control theory research communities. In this paper, we use a nonlinear dynamic model of the TCP RED congestion control algorithm to analyze and design active queue management (AQM) control systems. A linearized model of RED behavior around its nominal operating point which implicitly includes the delay in the control signal is derived. It is assumed that the system model is corrupted at the input and output by zero mean white Gaussian noise signals. An optimal state feedback stochastic controller is designed for the linearized model of the system in conjunction with a Kalman filter for state estimation. To illustrate the proposed design methodology, simulations results are presented and discussed. The proposed stochastic controller is applied to the nonlinear model of the system; Simulation results indicate that the proposed controller keeps the queue length bounded in an appropriate stochastic sense. Copyright © 2009 John Wiley & Sons, Ltd.     

Random early detection gateways for congestion avoidance

The authors present random early detection (RED) gateways for congestion avoidance in packet-switched networks. The gateway detects incipient congestion by computing the average queue size. The gateway could notify connections of congestion either by dropping packets arriving at the gateway or by setting a bit in packet headers. When the average queue size exceeds a present threshold, the gateway drops or marks each arriving packet with a certain probability, where the exact probability is a function of the average queue size. RED gateways keep the average queue size low while allowing occasional bursts of packets in the queue. During congestion, the probability that the gateway notifies a particular connection to reduce its window is roughly proportional to that connection's share of the bandwidth through the gateway. RED gateways are designed to accompany a transport-layer congestion control protocol such as TCP. The RED gateway has no bias against bursty traffic and avoids the global synchronization of many connections decreasing their window at the same time. Simulations of a TCP/IP network are used to illustrate the performance of RED gateways     

Exponential-RED: a stabilizing AQM scheme for low- and high-speed TCP protocols

This paper introduces and analyzes a decentralized network congestion control algorithm which has dynamic adaptations at both user ends and link ends, a so-called general primal-dual algorithm. We obtain sufficient conditions for local stability of this algorithm in a general topology network with heterogeneous round-trip delays. Then, as an implementation of this algorithm in the Internet, we introduce an AQM (Active Queue Management) scheme called Exponential-RED (E-RED), which outperforms RED and is inherently stable when combined with TCP-Reno or its variants for high-speed networks.     

一种支持区分服务的模糊公平分组丢弃算法

随机早期检测(RED)算法是目前Internet中广泛使用的一种缓存管理算法,对RED算法进行改进以提高公平性以及对网络动态变化的适应性一直是主动队列管理的研究重点之一。该文引入新的变量分享指数,取代单个业务流缓存占用量来表征不同业务流对网络资源的占用情况,以克服缓存占用量表征公平性的缺陷。同时,在无线网络中对分享指数的定义进行推广,使其同时兼顾公平性和系统性能(信道条件)。通过对分享指数和队列长度共同制定规则,提出了一种基于模糊逻辑控制的缓存管理算法。算法在根据缓存队列长度计算丢弃概率时,根据不同流对网络资源的占用情况(即分享指数)进一步决定增加或减小相应的丢弃概率,从而可利用不同流之间的差异以加速缓解拥塞,具有更好的自适应性和公平性。仿真表明,采用该算法后,系统性能得到改善。     

一种无线网络中基于ARQ的拥塞控制方法

提出了一种适用于无线网络的基于多拒绝自动请求重传（ARQ）算法的拥塞控制方法。谊方法结合随机早探洲（RED）算法，通过ARQ发送窗口和分割队列长度以及重传率进行拥塞控制。仿真表明，这种方法能预测链路拥塞，反馈链路拥塞程度，提高链路吞吐率。