一种新的加权公平队列调度算法

传统公平队列调度算法(WFQ、WRR等)普遍存在基于数据包的权重参数计算问题,由此产生的高复杂度使其难以获得广泛应用。该文提出一种新的加权公平队列调度算法,使用服务概率和随机数实现加权公平调度,显著降低了算法的复杂度。同时使用自适应服务概率计算解决了数据包变长度带来的不公平性。通过队列管理技术有效地提高了交换机的缓冲区利用率,并减小了排队延迟抖动。仿真结果证明了算法的有效性和实用性。     

队列调度算法在网络中的应用研究

作为保证QoS的一种重要手段,队列调度算法近年来引起了网络研究者的广泛关注。本文首先介绍了队列调度问题及一些常用的队列调度算法,然后提出一个非GPS模型的队列模型及调度算法——WDQ算法(Weighted Delay Queuing,基于权重的延迟队列),并且解释了这种算法能够有效抵抗通信量的突发,具有控制不同权重分组延迟的能力,对于提高和改善网络服务质量QoS方面的研究和网络运行情况的研究具有积极意义。     

随机公平队列对UDP洪流的抑制效果分析

随机公平队列(Stochastic Fairness Queueing,SFQ)是一种典型的公平队列调度算法.UDP洪流是实施DDOS攻击的一种主要攻击手段.研究了SFQ调度和网络中广泛应用的先到先服务(First Come First Server,FCFS)队列调度策略对UDP洪流攻击的抑制效果.基于多协议网络模拟平台NS2的仿真结果表明,FCFS调度难以对UDP洪流攻击产生有效的抑制作用,而SFQ调度却能在一定程度上抑制该攻击.     

支持组播的输入队列ATM交换机设计及其调度策略研究

目前基于输入队列技术的 ATM交换机的研究日益活跃 .输入队列单播调度算法的研究已经取得了较多研究成果 ,并已得到商业应用 .但输入队列组播调度算法的研究目标主要集中于提高吞吐量 ,而忽略了调度算法对组播流 Qo S的影响 ,如延迟等 .文中提出了一种支持组播功能的输入队列 ATM交换机的设计方案 ,并给出相应的输入队列组播调度算法 ,称为组播最长正则队列优先算法 (ML NQF) .调度算法 ML QNF具有改善吞吐量、满足Qo S需求和公平服务等特点 .     

一种新型的网络包公平调度算法的研究*

针对现有分组轮转法的局限,提出一种新的分组策略——虚拟权重队列分组策略。在这个新的分组策略的基础上,结合DRR和WF2Q,提出了虚拟权重队列分组轮转法。仿真实验表明,虚拟权重队列分组轮转调度算法比现有的分组轮转法拥有更好的延时性能和公平性能。     

一种队列管理和队列调度结合的算法

队列的管理和调度是网络处理中非常重要的一个环节.针对传统的队列算法分离队列管理和队列调度的缺点,提出了一种两种机制结合的算法.该算法以排队延时和系统吞吐量综合性能折中最优为目标,使用最优化决策的方法,根据数据源端的发送速率和网络节点中的缓冲队列长度调整带宽资源的分配.在仿真平台NS2下对算法进行了大量的仿真实验,最终的实验结果表明:按照网络性能公式(Power公式)的标准,该算法比传统的算法在性能上提高了近20%.因此该队列算法更能够提升网络处理的性能.     

基于服务时间的加权公平队列调度算法

针对已知存储系统调度算法无法保证服务资源公平分配的问题,提出一种基于服务时间的加权公平队列调度算法,该算法直接采用访问请求的服务时间作为服务资源分配的依据,其公平性非常接近于公平调度算法的理论极限,在负载波动的情况下仍能保持资源分配的稳定性。     

虚拟时钟调度算法研究

FIFO队列调度算法由于实现简单、执行效率高而在网络中得到大量的应用，但FIFO队列无法实现对资源的分配；男种调度算法公平队列调度则可以实现对带宽资源的公平分配，但是它存在可扩展性问题。而基于虚拟时钟的算法在实现对资源进行公平分配的同时具备良好的可扩展性，从而能够满足QoS控制中对于分组调度算法的需求。本文主要对一些基于虚拟时钟的度算法进行了分析和讨论，这也是进行QoS控制研究的基础。     

区分服务网络队列调度策略的研究与仿真

针对目前几种DiffServ(Differentiated Service)网络队列调度算法进行研究,提出一种动态队列调度策略来提高队列转发效率。通过动态调整队列权值实现队列的动态管理,从而改进网络资源的利用效率,改善DiffServ网络QoS。利用NS2模拟动态队列调度算法,实验表明动态队列调度算法有效地提高了区分服务网络的队列转发效率。     

高速分组交换网络中调度器的设计

为了满足迅猛发展的网络业务对网络服务质量提出的更高要求,使用高速分组网络交换机中的队列调度器可以有效地提供高质量的网络服务。通过采用分级式队列调度和四种队列调度算法有效地实现了队列调度器的设计。并且深入地比较和分析了队列调度器中多种队列调度算法的优缺点,尤其是对DRR调度算法进行了优化和改进。最后。对所设计的电路进行了仿真验证和电路综合,结果表明该调度器可以满足网络对服务质量的更高要求,并且能够应用到高速分组交换网络的调度器设计中。     

IPRPS——一种简单有效的设计加权公平排队算法的模型

PRPS是一种设计加权公平排队算法的数据包模型，Stiliadis指出PRPS具有与设计加权公平排队算法的理想模型－RPS相近的延迟和公平性特性，但实际上，在最坏情况下，PRPS与RPS会有很大的差距，首先指出这种差距的存在，同时通过调节数据包进入PRPS的时间，提出了一种简单有效地设计加权排队算法的模型－IPRPS，并证明了IPRPS具有与RPS几乎相同的延迟和公平性特性。     

一种选择性丢包机制的分析与设计

随机早期捡测算法(RED)在产生丢包时简单地丢弃到达的数据包，由于Web流占据了网络上75％左右的带宽，而Web流的特点是数据包比较少，这就使得早期丢包的效果难以体现。本文提出一种选择性丢包机制，引进一个类似公平队列的虚队列，检测发遥速率过大的流，筛选出丢包的候选链接，拥塞时丢弃候选链接在队列申的第一个连接的数据包。模拟实验结果表明，与队头丢包相比，采用选择性丢包的RED算法可进一步降低网关的丢包率，提高吞吐率，缩短Http的响应时间，提高队列的稳定性。     

一种短流优先的公平带宽分配机制

提出一种短流优先的公平带宽分配机制FPIP(fair PIP).通过区别处理短流和长流的报文,FPIP能够将带宽优先分配给短流,然后将剩余的带宽在长流之间公平分配.此外,FPIP采用主动队列管理机制AQM(active queue management)检测拥塞并控制队列长度.仿真结果表明,FPIP在保证公平性、控制队列长度、减小Web流的响应时间等方面具有良好的性能.     

Port partitioning and dynamic queueing for IP forwarding

With the increase of internet protocol (IP) packets the performance of routers became an important issue in internet/working. In this paper we examine the matching algorithm in gigabit router which has input queue with virtual output queueing. Dynamic queue scheduling is also proposed to reduce the packet delay and packet loss probability. Port partitioning is employed to reduce the computational burden of the scheduler in a switch which matches the input and output ports for fast packet switching. Each port is divided into two groups such that the matching algorithm is implemented within each pair of groups in parallel. The matching is performed by exchanging the pair of groups at every time slot. Two algorithms, maximal weight matching by port partitioning (MPP) and modified maximal weight matching by port partitioning (MMPP) are presented. In dynamic queue scheduling, a popup decision rule for each delay critical packet is made to reduce both the delay of the delay critical packet and the loss probability of loss critical packet. Computational results show that MMPP has the lowest delay and requires the least buffer size. The throughput is illustrated to be linear to the packet arrival rate, which can be achieved under highly efficient matching algorithm. The dynamic queue scheduling is illustrated to be highly effective when the occupancy of the input buffer is relatively high.Scope and purposeTo cope with the increasing internet traffic, it is necessary to improve the performance of routers. To accelerate the switching from input ports to output in the router partitioning of ports and dynamic queueing are proposed. Input and output ports are partitioned into two groups A/B and a/b, respectively. The matching for the packet switching is performed between group pairs (A, a) and (B, b) in parallel at one time slot and (A, b) and (B, a) at the next time slot. Dynamic queueing is proposed at each input port to reduce the packet delay and packet loss probability by employing the popup decision rule and applying it to each delay critical packet.The partitioning of ports is illustrated to be highly effective in view of delay, required buffer size and throughput. The dynamic queueing also demonstrates good performance when the traffic volume is high.     

General packet induced queueing schemes for reducing packet delays in ADSL routers with peer-to-peer file sharing applications

This paper proposes a class of queueing schemes named general packet induced queueing schemes (GPIQS) in ADSL routers to reduce the queueing delays of non-P2P packets. The objective of the proposed queueing schemes is to send out the general packets first as well as P2P packets are able to be sent in a bounded queueing delay. The proposed queueing schemes use the general packet to induce the transmission of P2P packets which are from the same client and arrived at the ADSL router before the general packet. The outbound order of the packets transmitted from a specific client is not altered in the proposed schemes. Two queueing schemes named general packet induced queueing scheme with single P2P queue (GPIQS-SQ) and general packet induced queueing scheme with multiple P2P queues (GPIQS-MQ) are proposed. The two proposed queueing schemes differ in the number of P2P queues. In order to prevent the unlimited waiting time of P2P packets, we introduced a variable called the largest number of preempting packets to send out the P2P packets in a bounded time. Simulation results show that the proposed queueing schemes may send out the packets from ADSL router efficiently and the average queueing delay is smaller than the common used first-come first-served algorithm. Specifically, the GPIQS-MQ performs better than the GPIQS-SQ method in terms of average queueing delay of non-P2P packets. We also found that the increased average queueing delay of P2P packets is small. Finally, the values of the largest number of preempting packets are discussed.     

区分服务中一种动态概率优先级调度算法*

提出了一种动态概率优先级算法DPP,针对一类对延时和丢包率要求相对较高的应用,根据AF1队列长度动态调整概率计算参数p,有效地解决了由于突发流量带来的QoS性能下降问题。不同实验环境下的仿真结果表明,DPP算法有效改善了突发性对分组平均排队延时的影响,减少了分组丢包率。     

Performance evaluation for DRED discrete-time queueing network analytical model

Due to the rapid development in computer networks, congestion becomes a critical issue. Congestion usually occurs when the connection demands on network resources, i.e. buffer spaces, exceed the available ones. We propose in this paper a new discrete-time queueing network analytical model based on dynamic random early drop (DRED) algorithm to control the congestion in early stages. We apply our analytical model on two-queue nodes queueing network. Furthermore, we compare between the proposed analytical model and three known active queue management (AQM) algorithms, including DRED, random early detection (RED) and adaptive RED, in order to figure out which of them offers better quality of service (QoS). We also experimentally compare the queue nodes of the proposed analytical model and the three AQM methods in terms of different performance measures, including, average queue length, average queueing delay, throughput, packet loss probability, etc., aiming to determine the queue node that offers better performance.     

一种精确度加强的主动队列管理算法BLUE+

主动队列管理是IP拥塞控制的一种重要机制,BLUE算法作为一种典型的主动队列管理算法,使用丢包和连接空闲事件来控制拥塞,但是其性能还不稳定。对BLUE算法进行了改进,提出了一种精确度加强的主动队列管理算法BLUE+,并将其应用于区分服务(DiffServ)模型。仿真表明BLUE+能够进一步提高对队列的控制精确度,改善BLUE算法的性能,并且能有效地支持区分服务。