基于AOS的Hurst-优先级自适应RED与动态调度算法

为有效传输空间数据系统中多类型、大容量、突发性的数据,基于高级在轨系统(AOS)虚拟信道复用技术,提出了一种自相似参数Hurst-优先级自适应的随机早检测(RED)与动态调度算法——HPRED-DS。该算法在队列管理中设计了基于Hurst参数与优先级的2级丢弃分组策略,在虚拟信道调度中设计了VIP/同步/异步混合的动态调度模式,并将队列管理与虚拟信道调度有效结合起来。实验结果表明该算法在保持高处理效率和吞吐率的基础上,稳定了队列长度,降低了排队延时和延时抖动,并能满足AOS中不同业务的传输要求。     

一种能有效支持QoS的光突发装配技术

提出了一种新的光突发装配技术，目的在于增强光突发交换(OBS)网络的服务质量(QoS)能力。该技术由自适应门限突发装配算法和基于优先级的随机化的偏移时间设置方案构成。该装配算法特别适合于多类别分组混合装配，能让所有类别的分组公平有效地使用装配能力，能较好地与IP层的QoS机制相匹配。偏移设置方案将突发控制分组(BCP)与突发数据(BP)间的偏移时间分成QoS偏移和随机偏移，前者由改进的JET协议按照有选择性的突发段丢弃机制(BSSD)确定，后者则由令牌桶机制确定。BSSD仅丢弃包含有低类别分组的突发段，而非整个突发。计算机仿真结果表明，本文提出的突发装配技术在性能上具有优越性。     

主动队列管理中的智能分组丢弃新机制

主动队列管理通过网络中间节点有控制的分组丢弃实现了较低的排队延时和较高的有效吞吐量,是TCP端到端拥塞控制近来研究的一个技术热点.已有的大多数算法在判定分组丢弃时大都沿袭了RED的概率丢弃机制,具有一定计算复杂度的随机数生成过程不利于路由器性能的优化.在本文中,我们首先定义了拥塞指数这一新的测度变量来量化描述网络的拥塞状态.接着,利用模糊逻辑设计了一种新的智能分组丢弃机制,离线的合成推理使得分组丢弃的判定仅需要简单的查表操作和比较运算即可完成,为优化路由器的性能提供了便利.数字仿真的结果表明:智能分组丢弃机制的性能优于经典的RED算法,控制队列的能力强,鲁棒性好,稳定工作域大,能很好地抵抗突发性和非弹性业务的干扰,适合工作在瞬息万变的动态网络环境中.     

一种改进的主动队列调度RED算法

本文在分析RED利用EWMA形式计算平均队列长度的局限性的基础上,提出了一种改进的RED算法。该改进RED算法在计算平均队列长度时考虑了当前队列长度的真实情况,并将两者结合起来进行丢弃决策。仿真结果表明改进RED算法在分组丢弃比例和链路利用率上部优于RED。     

光突发交换中冲突解决的GHA-TS机制

提出了一种新型的冲突解决机制--GHA-TS(priority-based grouping and hybrid-assembly with tail segment)机制,它采用基于优先级的分组复合封装策略,并根据偏射路由阀值选择尾部分段丢弃或偏射路由策略进行冲突解决.仿真结果表明,GHA-TS机制能够有效降低光突发交换网络的丢包率,尤其是高优先级IP报文的丢失率,较好地支持了光突发交换网络的QoS要求.     

基于平衡二叉树的优先级队列管理

随着网络的发展,网络流量越来越大,拥塞问题越来越严重,各种队列管理算法应运而生,然而这些算法在丢弃数据包时却忽略了数据包的优先级或对优先级队列的处理不够完善。文章先介绍了优先级队列以及一些优先级队列的管理办法,然后提出利用平衡二叉树这种数据结构实现对优先级队列的入队列和出队列操作,最后提出一种对RED(随机提前探测)算法的改进方案。     

一种新的实现区分服务的可扩展缓存管理算法

目前Internet网络中采用的缓存管理策略大多为丢尾(Drop tail)算法,并不能适应区分服务模型的要求;而RED及其改进算法CHOKe也不能提供公平性和相对优先级的保证。该文简要地分析了目前常见的缓存管理算法RED以及CHOKe所存在的不足,提出了一种基于区分服务模型的新型缓存管理算法D-CHOKe。该算法提供了公平性和相对优先级的保证,并且保持下现有IP网的可扩展性。仿真试验表明,该算法能够较好地满足区分服务的要求,为不同优先级的流分配不同的带宽。     

光突发交换网络中的闭环竞争解析

为改善光突发交换网络(OBS)的性能,深入探讨了光突发交换网络中的闭环竞争解析,提出了OBS网络中的主动资源预留方案OBS—RED和显式竞争通知方案OBS—ECN。OBS—RED采用随机早期丢弃策略,即根据数据信道拥塞情况,随机早期地丢弃控制分组。OBS—ECN的实现需要OBS—RED的支持。在OBS—ECN中,不是随机丢弃控制分组,而是将这一信息显式地通知边缘节点,边缘节点再作相应的处理。OBS—RED与OBS—ECN的应用,有利于提高网络吞吐量和链路带宽资源利用率,大大减少数据突发的阻塞概率。     

一种新型分组过滤器的存储和匹配方案设计

PF(分组过滤器)是EPS(演进型分组系统)的重要组成部分。在详细分析EPS中PF存储方案的基础上,给出了一种新的基于EPS承载的PF储存和匹配方法,将PF按照对应的承载标识存储到承载信息单元中,同时为了实现基于PF优先级的IP分组数据包匹配,建立了按照优先级排序的PF信息表,利用PF信息表可以快速地找到对应优先级的PF存储位置,完成IP数据包的匹配。     

支持QoS的自适应门限复合光突发装配技术

该文提出了一种新的光突发装配技术,该技术由自适应门限突发装配算法和基于优先级的随机 化的偏移时间设置方案构成.该装配算法特别适合于多类别分组混合装配,能让所有类别的分组公平有效地使用装配能力,能较好地与IP层的QoS机制相匹配。计算机仿真结果表明该文提出的光突发装配技术在性能上具有一定优越性.     

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。     

自相似流量的主动队列管理算法

该文提出了一种替代随机早期检测(RED)的主动队列管理算法:信号能量的小波分解(wavelet-decomposed signal energy, WDSE)算法。WDSE能够有效地对自相似流量进行拥塞检测和管理。采用小波的二阶子段滤波测量输入流量的能量,基于小波的多分辨率分析可以对到达流量的短期和长期波动进行预报,重新调整主动队列管理的丢弃概率。WDSE可以避免先前主动队列管理所难以解决的参数选择问题,如RED等。该文比较了WDSE和RED的动态性能,显示WDSE能够有效改善系统的暂态特性。仿真证明WDSE比RED能更快地响应负载的变化。此外,WDSE在控制瞬时队列长度的稳态值也具有更好的鲁棒性。     

RED分组丢弃算法性能研究

 本文研究了在ATM交换机上实现的RED算法的性能.在固定有效带宽、时变有效带宽情况下和同种、异种业务环境下,研究了RED算法的通过率、公平性和时延等性能.经研究表明:RED算法有必要与EPD算法相结合,构成RED+EPD算法.采用RED+EPD算法的ATM交换机通过控制平均排队长度,有效地减小了交换机的平均排队时延.通过与其他分组丢弃算法进行性能比较表明:采用RED+EPD算法的ATM交换机,可提供比EPD算法略高的通过率,更好的公平性和更低的排队时延,能较好地支持具有时延要求的业务.     

FQL‐RED: an adaptive scalable schema for active queue management

In a potentially congested network, random early detection (RED) active queue management (AQM) proved effective in improving throughput and average queuing delay. The main disadvantage of RED is its sensitive parameters that are impossible to estimate perfectly and adjust manually because of the dynamic nature of the network. For this reason, RED performs differently during different phases of a scenario and there is no guarantee that it will have optimal performance. Giving adaptability to RED has been the subject of broad research studies ever since RED was proposed. After a substantial study of AQM schemes and presenting a novel categorization for so‐called modern approaches utilizing artificial intelligence tools to improve AQM, this paper proposes an algorithm enhancing RED as an add‐on patch that makes minimal changes to the original RED. Being built on the basis of AQM schemes like ARED and Fuzzy‐RED, this algorithm inherits adaptability and is able to adjust RED inaccurate parameters regarding network traffic status, trying to optimize throughput and average queuing delay in a scenario. This algorithm is a Q‐learning method enhanced with a fuzzy inference system to provide RED with self‐adaptation and improved performance as a result. Given the name of FQL‐RED, this algorithm outperformed RED, ARED, and Fuzzy‐RED, as the OPNET simulations show. Copyright © 2010 John Wiley & Sons, Ltd.     

Tuning RED for Web traffic

We study the effects of RED on the performance of Web browsing with a novel aspect of our work being the use of a user-centric measure of performance: response time for HTTP request-response pairs. We empirically evaluate RED across a range of parameter settings and offered loads. Our results show that: (1) contrary to expectations, compared to an FIFO queue, RED has a minimal effect on HTTP response times for offered loads up to 90% of link capacity; (2) response times at loads in this range are not substantially affected by RED parameters; (3) between 90% and 100% load, RED can be carefully tuned to yield performance somewhat superior to FIFO, however, response times are quite sensitive to the actual RED parameter values selected; and (4) in such heavily congested networks, RED parameters that provide the best link utilization produce poorer response times. We conclude that for links carrying only Web traffic, RED queue management appears to provide no clear advantage over tail-drop FIFO for end-user response times     

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     

A comparison of active queue management algorithms using the OPNETModeler

A number of active queue management algorithms for TCP/IP networks such as random early detection (RED), stabilized RED (SRED), BLUE, and dynamic RED (DRED) have been proposed in the past few years. This article presents a comparative study of these algorithms using simulations. The evaluation is done using the OPNET Modeler, which provides a convenient and easy-to-use platform for simulating large-scale networks. The performance metrics used in the study are queue size, packet drop probability, and packet loss rate. The study shows that, among the four algorithms, SIZED and DRED are more effective at stabilizing the queue size and controlling the packet loss rate while maintaining high link utilization. The benefits of stabilized queues in a network are high resource utilization, bounded delays, more certain buffer provisioning, and,traffic-load-independent network performance in terms of traffic intensity and number of TCP connections     

分级指导随机提早丢弃队列管理机制CGRED

本文提出的分级指导随机提早丢弃CGRED是在因特网上为用户提供有区别服务的单队列管理机制,它同时满足了对服务质量的精细控制和实现简单性两方面的需求.CGRED采用在线测量的方法跟踪业务类的实际带宽占用情况,根据给定的优先级关系确定调整业务类的指导策略,并以采用自适应算法计算得到的丢弃指导概率作为分组丢弃概率的边界,成功地解决了将不同业务类的实际带宽占用情况转化成如何丢弃不同业务类分组的实际操作.仿真结果表明CGRED是一种能有效提供DiffServ的实用网络控制机制.     

Modified RED gateways under bursty traffic

We propose modified random early detection (MRED) gateways for congestion avoidance in TCP/IP networks. MRED aims at providing better control over the burstiness level while remaining the advantages of RED. We use ns2 to simulate a series of network configurations and the numerical results demonstrate that MRED can achieve higher link utilization compared to RED without sacrificing its advantages in all simulation scenarios. The improvement becomes more significant under bursty traffic.     

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.