Integrated Random Early Detection for Congestion Control at the Router Buffer

This paper proposed an Integrated Random Early Detection(IRED)method that aims to resolve the problems of the queue-based AQM and loadbased AQM and gain the benefits of both using indicators from both types.The arrival factor(e.g.,arrival rate,queue and capacity)and the departure factors are used to estimate the congestion through two integrated indicators.The utilized indicators are mathematically calculated and integrated to gain unified and coherent congestion indicators.Besides,IRED is built based on a new dropping calculation approach that fits the utilized congestion indicators while maintaining the intended buffer management criteria,avoiding global synchronization and enhancing the performance.The results showed that IRED,compared to RED,BLUE,ERED,FLRED,EnRED and DcRED,decreased packet delay and loss under various network status.Specifically,the results showed that in heavy and moderate traffic,the proposed IRED method outperformed the state-of-the-art methods in loss and delay by 18% and 10.6%,respectively.

EFRED: Enhancement of Fair Random Early Detection Algorithm

Quality of Service (QoS) generally refers to measurable like latency and throughput, things that directly affect the user experience. Queuing (the most popular QoS tool) involves choosing the packets to be sent based on something other than arrival time. The Active queue management is important subject to manage this queue to increase the effectiveness of Transmission Control Protocol networks. Active queue management (AQM) is an effective means to enhance congestion control, and to achieve trade-off between link utilization and delay. The de facto standard, Random Early Detection (RED), and many of its variants employ queue length as a congestion indicator to trigger packet dropping. One of these enhancements of RED is FRED or Fair Random Early Detection attempts to deal with a fundamental aspect of RED in that it imposes the same loss rate on all flows, regardless of their bandwidths. FRED also uses per-flow active accounting, and tracks the state of active flows. FRED protects fragile flows by deterministically accepting flows from low bandwidth connections and fixes several shortcomings of RED by computing queue length during both arrival and departure of the packet. Unlike FRED, we propose a new scheme that used hazard rate estimated packet dropping function in FRED. We call this new scheme Enhancement Fair Random Early Detection. The key idea is that, with EFRED Scheme change packet dropping function, to get packet dropping less than RED and other AQM algorithms like ARED, REM, RED, etc. Simulations demonstrate that EFRED achieves a more stable throughput and performs better than current active queue management algorithms due to decrease the packets loss percentage and lowest in queuing delay, end to end delay and delay variation (JITTER).

AN EFFECTIVE NETWORK CONGESTION CONTROL METHOD FOR MULTILAYER NETWORK

The congestion control problem in a single node network has been solved by the nonlinearfeedback control method,which has been proven to be effective and robust for different router’s queuesize.However,these control models are based on the single layer network architecture,and the sendersand receivers are directly connected by one pair of routers.With the network architecture being moreand more complex,it is a serious problem how to cooperate many routers working in the multilayernetwork simultaneously.In this paper,an effective Active Queue Management(AQM)scheme toguarantee the stability by the nonlinear control of imposing some restrictions on AQM parameter inmultilayer network is proposed.The nonlinear control can rely on some heuristics and network trafficcontrollers that appear to be highly correlated with the multilayer network status.The proposedmethod is based on the improved classical Random Early Detection(RED)differential equation and atheorem for network congestion control.The theorem proposed in the paper proved that the stability ofthe fluid model can effectively ensure the convergence of the average rate to its equilibrium pointthrough many routers in multilayer network.Moreover,when the network capacity is larger,theproposed scheme can still approach to the fullest extensibility of utilization and ensure the stability ofthe fluid model.The paper reveals the reasons of congestion control in multilayer network,provides atheorem for avoiding network congestion,and gives simulations to verify the results.

UDP业务引起的网络拥塞问题研究

用UDP作为传输层协议的应用日益增多，其中包括用IP传输视频、音频的各种应用。UDP业务的增加会给网络带来新的拥塞问题。提出了一种基于随机早期检测技术(RED)的方案，对最终解决UDP业务导致的网络拥塞问题具有一定的参考价值。

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 pre- dominance 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. Theo- retical 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.

BIFURCATIONS AND CHAOS CONTROL IN TCP-RED SYSTEM

Objective Analyzing the nonlinear dynamics of the TCP-RED congestion control system is of great importance. This study will help investigate the loss of stability in Internet and design a proper method for controlling bifurcation and chaos in such system. Methods Based on bifurcation diagram, the effect of parameter on system performance is discussed. By using the state feedback and parameter variation strategy, a simple real time control method is proposed to modify the existing RED scheme. Results With our control method, the parametric sensitivity of RED mechanism is attenuated. Moreover, a sufficient condition on the robust stability of the system is also derived to adjust the parameters in TCP-RED system. Conclusion The proposed method has the advantages of simple implementation and unnecessary knowledge of the exact system.

主动队列管理RED算法改进与实验仿真研究

分析了RED及其改进算法的原理和局限性,提出了一种非线性高阶RED拥塞控制机制。该算法利用一个高阶分组丢弃函数,在下限阈值附近以较低的概率标记丢弃分组,在上限阈值附近迅速提高分组的标记丢弃概率。并对网络仿真器NS2进行扩展,通过系列仿真实验验证了改进算法有效提高了网络性能。

基于路由器的RED和Droptail算法比较

弃尾(Droptail)和随机早期检测RED(RandomEarlyDetection)算法是目前路由器中采用的两种重要的队列管理算法。为了在路由器中广泛应用RED算法取代Droptail算法提供依据,对两种算法的性能和实现条件进行了对比研究。使用网络仿真平台NS2(NetworkSimulationVersion2),首次在缓冲区大小相同的条件下,证明了RED算法在网络拥塞控制、提高网络性能及利用率等方面较Droptail算法有很大提高。仿真结果表明,RED算法与Droptail算法相比,平均队长缩短32%;传输延时减小50%以上;网络净吞吐量提高13%;丢包率降低13%;并能在一定程度上避免发生"全局同步"。

基于RED算法的非线性拥塞控制

由于RED算法是采用丢包率随平均队列长度线性变化的方法,因此导致网络在拥塞并不严重的时候丢包率较大,在拥塞比较严重的时候丢包率较小,拥塞控制能力较低。该文提出非线性平滑算法通过对RED算法的丢包率函数进行非线性平滑,在最小阈值时丢包率增长速度比较小,在最大阈值时丢包率增长速度比较大,有效地控制了平均队列长度,具有较好的拥塞控制能力。NS2仿真结果表明该算法对丢包率、端到端时延、吞吐量以及时延抖动等性能均有较明显的提高。

改进的随机提前检测算法

研究了一般网络情况下有效配置 RED路由器参数的问题 .将一个瓶颈结点为 RED路由器的网络系统抽象为一个闭环负反馈控制系统模型 ,指出由一组缺省静态参数配置的 RED路由器不能理想地适应网络负载在大范围变化的情况 .提出了一种根据网络属性特征自配置参数的改进 RED算法 .模拟结果表明 ,改进的 RED算法比原 RED算法能更好地适应各种网络容量及网络负载情况 。

参数自适应的随机早期检测算法

随机早期检测(Random Early Detection, RED)是一种广泛应用于包交换网络的主动队列管理技术,它通过保持较小的平均队列长度,在缓冲区溢出前主动丢包,降低路由器的丢包率,保持较低的服务延迟,避免缓冲区锁定,提高网络的利用率。但是RED严重依赖于参数的设置。该文根据保持网络流量平稳的丢包率和路由队列的变化提出了一种自适应地调节参数的RED改进算法。模拟实验的结果表明,自适应地调节参数提高了RED的适应性,降低了数据包排队延时和丢包率,提高了链路利用率。

基于路由器的网络拥塞控制策略研究

因特网的迅速发展使拥塞控制问题日益得到人们的重视 ,传输控制协议 (TCP)在拥塞控制中一直发挥着至关重要的作用 ,但路由器是网络中的核心部件 ,是网络状态更直接的感受者。为实现网络的更有效的控制 ,路由器端处也应采取相应的措施。本文讨论了路由器端的几种拥塞控制方案 ,并分析比较了各种方案的优缺点。

基于RED分组丢失历史方法的非TCP流鉴别

随机早期检测(RED)是IETF推荐的一种基于路由器的有效的主动队列管理算法,但是在某些情况下,一些数据量很大的高带宽流量会大量占用带宽,从而导致了各流量之间带宽分配的不公平性,甚至产生拥塞崩溃。该文从RED的丢包历史出发,研究了一种在发生拥塞时鉴别出高带宽流量的方法,并通过仿真证实了此方法的有效性。

按端到端连接调度的网络拥塞控制机制

针对越来越多网络应用不采用端到端拥塞控制机制而导致非公平占用网络带宽问题，介绍了在路由器内部实现基于连接调度的增强拥塞控制方法．路由器使用公平排队调度算法代替传统的先来先服务调度算法，可隔离和保护基于漏桶控制的网络连接．但采用传输控制协议（ＴＣＰ）连接对数据包丢失敏感，路由器使用公平排队调度算法还需要结合相应的缓冲管理方法，才能保证ＴＣＰ连接获取公平的吞吐量．讨论了基于连接的最长排队数据包丢弃的缓冲管理方法．模拟结果表明。

一种基于连接的增强拥塞控制机制

文中针对越来越多的网络应用不采用端到端拥塞控制机制而导致非公平占用网络带宽问题，介绍了在路由器内部实现基于连接调度的增强拥塞控制方法．路由器使用公平排队调度算法代替传统的先来先服务调度算法，可隔离和保护基于漏桶控制的网络连接．但采用基于窗口反馈拥塞控制机制ＴＣＰ连接会对数据包丢失敏感，路由器使用公平排队调度算法还需要结合相应的缓冲管理方法，才能保证ＴＣＰ连接获取公平的吞吐量．文中还讨论了基于连接的排队数据包公平缓冲丢弃的缓冲管理方法．模拟结果表明，公平排队调度算法结合文中所提出的缓冲管理方法比随机提前检测缓冲管理方法可更好地改进拥塞控制性能．

RF-RED:一种速率公平的RED改进算法

为了提高响应流和非响应流之间的公平性,提出了一种基于速率公平的RED改进算法——RF-RED(ratefairness random early detection).该算法在路由器端计算UDP流的平均速率并与TCP友好流速率进行比较,根据比较结果动态调整UDP流和TCP流的最大丢包率,最后使用RED算法分别更新UDP流和TCP流的实际丢包率.通过使用RF-RED算法,UDP流在瓶颈链路上成为TCP友好流,同时瓶颈带宽得到了公平利用.仿真结果验证了该算法的有效性.

Internet主动队列管理算法研究

路由器的拥塞控制策略是采用主动队列管理算法(AQM),最广泛被采用的主动队列管理算法是随机早期检测(RED)算法。文中详细讨论了RED算法,并剖析了基于RED算法的几种改进策略,经比较它们的优点及其存在的主要缺陷后,提出了进一步研究主动队列管理算法的方向。

基于时间槽的自相似流量随机早检测算法——SFRED

分析研究了网络流量的自相似和长相关性,并基于分形布朗运动模型导出了自相似流量环境RED算法分组丢失概率的一种计算方法,从而提出了基于时间槽的自相似流量随机早检测队列管理算法SFRED。该算法在每个时间槽内计算一次分组丢失概率,大大降低系统负担。NS2仿真实验表明SFRED算法性能明显优于RED,能够很好地在自适应流背景下控制队列长度,并具有良好的吞吐量性能。

随机早期检测算法研究

RED消除了全局同步现象,较大地提高了物理线路的利用率,减少了对突发业务的偏见。但在有大量活跃TCP连接时,RED不能有效估计拥塞的严重性,从而降低链路利用率。针对这些问题提出了RED的改进算法。仿真表明,该算法在突发业务下能对拥塞作出更及时有效的反应,并能保证链路利用率。

主动队列管理中PI控制的分析与改进

主动队列管理是一个控制过程,它由核心路由器通知TCP源端管理时延并对队列加以利用,是一个反馈控制问题。该文在TCP拥塞控制动态模型的基础上,分析了随机提前检测(RED)机制和其队列平均的不利性,提出可采用PI控制进行队列管理。对PI控制,可将丢弃数据包的概率从几何随机数改进为标准随机数,经网络仿真器仿真,结果表明,验证了该文提出的这一改进效果。