On the behavior of ECN/RED gateways under a large number of TCP flows: Limit theorems

We consider a discrete-time stochastic model of an ECN/RED gateway where competing TCP sources share the link capacity. As the number of competing flows becomes large, the asymptotic queue behavior (normalized by the number of flows) at the gateway can be described by a simple recursion and the throughput behavior of individual TCP flows becomes asymptotically independent. A Central Limit Theorem complement is also presented, yielding a more accurate characterization of the asymptotic queue size. These results suggest a scalable yet accurate model of this complex large-scale stochastic feedback system, and crisply reveal the sources of queue fluctuations. This work was prepared through collaborative participation in the Communications and Networks Consortium sponsored by the U.S. Army Research Laboratory under the Collaborative Technology Alliance Program, Cooperative Agreement DAAD19-01-2-0011. This work was also supported by the Space and Naval Warfare Systems Center—San Diego under Contract No: N66001-00-C-8063. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Laboratory or the U.S. Government.     

一种新的快速响应的AQM算法

该文应用控制理论,设计了具有快速响应特征的比例积分(Proportional-Integral, PI)控制器,并以此提出了一个新的主动队列管理(Active Queue Management, AQM)算法,称为Active PI算法(简称A-PI)。A-PI用一组参数实现快速响应,用另一组参数保证队长稳定,使用门限值实现两组参数间平滑切换,算法实现简单。理论分析和仿真实验表明,A-PI算法在保证队长稳定的同时实现了对不同网络环境的快速响应。     

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 rat...     

无线多媒体网络中自适应拥塞控制算法的研究

提出了一种适用于采用无线接入多媒体流的拥塞控制算法,简称adaptive-MQWB(adaptivemediaQoSandwirelessbandwidth)。该算法依据当前带宽的动态变化率,在满足多媒体传输的最大时延的前提下,以最佳目标队长为实现目标,寻求最优的主动队列管理方案。仿真结果表明,与目前已有的MADR、tuned-RED算法相比,adaptive-MQWB算法在带宽动态变化的自适应性和多媒体传输时延的QoS保证方面都表现出更好的性能优势。     

基于相对熵的区间Pythagorean模糊多属性AQM决策方法及其应用

针对决策信息为区间Pythagorean模糊数,属性权重不完全确定的多属性决策问题,提出了一种基于相对熵的AQM决策方法。首先,提出区间Pythagorean模糊数的相对熵,计算了各方案与区间Pythagorean模糊正理想方案和负理想方案间的相对熵,据此构建了基于方案相对满意度最大的非线性规划属性权重确定模型;其次,针对每个属性,利用新的区间Pythagorean模糊数得分函数计算方案的0-1优先关系矩阵,依据AQM方法对所有0-1优先关系矩阵进行融合得到合成0-1优先关系矩阵,并确定了方案的综合度,由此获得方案的排序。最后,以软件开发项目的选取为实例说明了该方法的可行性和有效性。     

A compensated PID active queue management controller using an improved queue dynamic model

Beside the major objective of providing congestion control, achieving predictable queuing delay, maximizing link utilization, and robustness are the main objectives of an active queue management (AQM) controller. This paper proposes an improved queue dynamic model while incorporating the packet drop probability as well. By applying the improved model, a new compensated PID AQM controller is developed for Transmission Control Protocol/Internet Protocol (TCP/IP) networks. The non‐minimum phase characteristic caused by Padé approximation of the network delay restricts the direct application of control methods because of the unstable internal dynamics. In this paper, a parameter‐varying dynamic compensator, which operates on tracking error and internal dynamics, is proposed to not only capture the unstable internal dynamics but also reduce the effect of uncertainties by unresponsive flows. The proposed dynamic compensator is then used to design a PID AQM controller whose gains are obtained directly from the state‐space representation of the system with no further gain tuning requirements. The packet‐level simulations using network simulator (ns2) show the outperformance of the developed controller for both queuing delay stability and resource utilization. The improved underlying model leads also to the faster response of the controller. Copyright © 2013 John Wiley & Sons, Ltd.     

一种基于IP网络的拥塞控制调度算法

文中在TCP基于窗口的端到端的拥塞控制算法和IP层拥塞控制算法上提出了一种改进的增强型非线性比例积分算法,该算法主要解决PID算法的参数设置、鲁棒性和算法敏感性问题,减少了PID算法的参数设置.改进的算法采用了内模控制和优化控制来实现算法的稳定性.通过仿真实验证明提出的算法有快的收敛速度和稳定性,提高了算法的鲁棒性.     

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。     

一种基于预测PI控制器的自相似网络主动队列管理算法

近年研究发现网络中的业务量呈自相似特征,这种自相似特征显著影响网络的流量控制与排队性能,本文在自相似网络流量可预测的基础上,利用线性回归分析理论进行流量预测,并应用控制理论中的预测PI控制器原理设计了动态矩阵PI控制主动队列管理(Dynamic Matrix PI Control-Active Queue Management,简称DMPIC-AQM)算法,以克服队列的剧烈振荡,保持队列稳定在期望的长度.仿真实验结果表明,DMPIC-AQM算法在网络流量剧烈变化和小期望队列长度的情形下,DMPIC-AQM算法明显优于RED与PI算法.     

REDu:一种新的识别并惩罚非适应流的主动式队列管理算法

本文提出一种新的主动式队列管理算法——热度算法(REDu).算法深入挖掘非适应流与适应流本质区别,利用CHOKe命中、RED丢弃等信息预选非适应流,通过热度升降机制计算一种新的部分流状态——热度,以此识别并惩罚非适应流.基于ns-2的仿真实验显示,与其他几种主动式队列管理算法相比,REDu具有更准确的识别并惩罚非适应流的能力,对适应流提供更好的保护,网络的鲁棒性也显著提高.