Active Queue Management Exploiting the Rate Information in TCP-IP Networks

In this paper, we propose a new mechanism called explicit rate notification(ERN) to be used in end-to-end communications. The ERN scheme encodes in the header of transmission control protocol(TCP) packets information about the sending rate and the round trip time(RTT) of the flows. This new available information to the intermediate nodes(routers) is used to improve fairness, increase utilization, decrease the number of drops, and minimize queueing delays. Thus, it induces a better management of the queue. A comparison of our scheme with preexistent schemes, like the explicit congestion notification scheme, shows the effectiveness of the proposed mechanism.

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.

TCP网络的自适应神经滑模控制

针对TCP网络的拥塞控制问题,考虑了TCP负载和往返时延具有较大的突发性和时变性的情况,结合滑模控制与RBF神经网络提出了一种主动队列管理算法。考虑到网络系统参数是未知时变的,采用RBF神经网络逼近网络系统参数,从而使得主动队列管理算法易于实现。依据李雅普诺夫稳定性理论设计了RBF神经网络权值的自适应律,使得网络系统参数得到了较好的估计。采用RBF神经网络的输出作为滑模控制器的参数设计了一种主动队列管理算法,使得网络系统是渐近稳定的。仿真结果表明所提出的算法与比例积分控制器和传统的滑模控制器相比具有较快的响应和稳定的队列长度,在网络参数变化时仍能获得较好的鲁棒性。

多层网TCP-RED非线性流体模型的高效网络拥塞控制

提出了一种多层网络拥塞控制方法,该方法基于流体模型的微分方程设计多层网络拥塞控制.此外,该方法利用流体模型的稳定性保证网络性能参数的均值在多层网络环境及大数据流的情况下向平衡点收敛,同时也有效限制了AQM参数的设置.理论分析和仿真结果证明了这种网络拥塞控制方法能在多层网络中避免拥塞,并当网络出现大数据流时,该多层AQM系统能充分利用网络带宽及保持路由器队列长度的相对稳定.

A NOVEL MARKOV ANALYTICAL MODEL FOR THE TCP/AQM SYSTEMS

A novel closed-loop feedback TCP/AQM(Transfer Control Protocol/Active Queue Management) model is proposed in this paper using a discrete-time Markov chain,and a way to calculate the equilibrium distribution of this model is given.In the model,system time is divided into time slots,the bottleneck router queue model and TCP window size model in each slot are analyzed.Finally,by combining adjacent slots,an integrated TCP/AQM analytical model is developed.By this model,the average values of packets dropping ratio and queue length in the router and TCP sending rate can be estimated,hence,this model could be a useful tool for the analysis of AQMs and support the development of new AQM schemes theoretically.The proposed TCP/AQM model is extended to a TCP-UDP(Control User Datagram Protocol)/AQM model,to analyze the TCP/AQM system performance when UDP flows exist.By implementing this model on Matlab,we compare its solutions to NS2 simulated solutions,then the validity of the model to analyze the closed-loop feedback TCP/RED(Random Early Detection) system is verified.

Integral sliding-mode robust observer-based congestion control for wireless access networks

Designing a robust active queue management(RAQM)is mandatory to avoid congestion in networks with wireless access links,because transmission control protocol(TCP)can detect con-gestion after its occurrence in a communication network and wireless links suffer from bottleneck capacity variations caused by fading and packet error rate(PER)in the acknowledgement pack-ets.Furthermore,the average window size cannot be measured explicitly from the output signal and input and state delay are imposed to a network,which complicate theRAQMdesign problem in nonlinear models.So,the main contribution of this study is to design a robust observer based control procedure based on integral sliding mode protocol to estimate the average window size,to control congestion in a TCP/RAQM network and to compensate input and state delay.Sim-ulation results via professional simulator NS-2 and SIMULINK confirm that the procedure can effectively estimate the window size and can robustly avoid congestion.

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.

基于传输控制协议的无线自组网主动队列管理建模

主动队列管理(AQM)通常研究队列控制器的设计.作为被控对象,传输控制协议(TCP)往往利用网络仿真器(NS)的仿真实现,因此有必要研究无线自组网的TCP及AQM特性.基于TCP窗口加性增-乘性减算法及排队原理,推导了TCP窗口及队列的微分方程,再基于比例积分AQM控制,推导了拥塞丢弃概率的微分方程,通过建立联立微分方程组,提出了Ad Hoc网络TCP/AQM微分模型.对比仿真显示,新模型能较好地估计无线自组网的性能.模型研究也表明,网络跳数,无线丢失和过小的队列成为AQM性能瓶颈,队列信息则有助于TCP区分无线自组网的拥塞丢弃与无线丢失.

一类不确定离散网络系统的全局滑模控制

针对动态传输控制协议(transmission control protocol,TCP)网络的拥塞问题,基于离散全局滑模控制理论设计了一种主动队列管理(active queue management,AQM)算法,该算法消除了滑模控制的到达阶段,保证网络系统在整个控制过程中的鲁棒性。为了减弱离散指数趋近律的抖振现象,给出了一种改进的滑模趋近律,使得复杂的网络系统具有良好的性能。仿真结果验证了所设计的控制器对活动的TCP连接数、链路带宽及往返时延的不确定性具有很强的稳定性和鲁棒性。

一种改进的CSFQ算法的设计与仿真

针对CSFQ算法存在的对TCP流的抑制及缓存策略等问题,提出采用ARED作为缓存管理的CSFQ改进算法A-CSFQ,并在多瓶颈链路下对其性能进行仿真。仿真结果表明,改进算法在保持CSFQ其他优点的基础上,显著减弱了对TCP流的抑制作用,提高了其对TCP流的公平性。

Internet拥塞控制策略的研究现状与展望

随着Internet的迅速发展,服务质量(QoS)正成为当前研究的热点之一。为了达到QoS性能指标的要求,拥塞控制策略成为确保Internet稳定性和健壮性的关键。本文在总结前人研究成果的基础上,对未来拥塞控制的发展做了有益探索。