基于效用最优化的多路径网络资源公平分配

网络资源最优分配除了要提高资源的利用率外,还应该实现面向服务、以用户为中心的资源分配目标,从而达到网络资源的公平分配,最大程度的满足用户的满意度.为了实现上述分配目标,文中考虑了多路径网络的资源公平分配问题,将多路径网络效用最大化模型分解为3个独立的子问题,而每个子问题其实对应于互联网体系结构的一层,并阐述了各个子问题的经济学含义.分析了用户所支付的价格和路径所收取的价格之间的关系,并提出了一类流量控制算法,通过该算法可以得到网络资源的最优公平分配.同时,考虑了算法在实际网络中的具体实现,并提出了基于窗口的流量控制机制.     

动态调整调度配额的TCSN调度算法*

针对列车控制与服务网（TCSN）的区分服务需求,进行了调度算法研究,提出了一种基于动态调整调度配额的算法DWDRR。该算法在原有的WDRR（加权差额轮询算法）算法基础上增加了调度配额的计算,并根据队列的数据流量到达率、时延优先级、丢包优先级和网络的当前状况综合地决定各个队列的调度配额,实现比例公平的调度。并通过仿真分析证明该调度算法可以根据各队列在不同网络状态下流量到达率、优先级动态地决定队列的调度配额,从而满足TCSN根据不同到达率、优先级进行区分服务的需求。     

基于源抑制的内网流量自适应控制算法研究

针对源抑制机制在内网流量控制中存在的带宽利用率不高的问题,提出一种基于源抑制的内网流量自适应控制算法。该算法在网关上监视网络流量,当总流量小于阈值时,不执行流量控制;当总流量超过阈值时,开始统计每个用户的流量,找出流量较大的用户,对于下载流量直接在网关上限速,对于上传流量通知接入交换机控制用户流量。在Linux中实现基于源抑制的内网流量自适应控制算法,并对其进行测试,结果表明该算法能够有效控制内网流量,实现带宽公平和高效利用。     

基于流量隔离的公平聚集器

为实现对微流的最差延迟最早聚集,并对聚集完成的宏流进行过滤与排序,实现宏流公平调度,提出基于流量隔离的公平聚集器(FAFI)。FAFI解决了在基于流量聚集调度模式中,同一宏流内部各竞争微流之间的突发流量对数据包传输延迟产生影响的问题。通过严格的数学推理与演算,证明FAFI的有效性。仿真实验验证了对FAFI模型的定量分析结果和FAFI模型的性能。     

改进WFQ算法在列车网络调度中的应用研究

随着我国轨道交通迅猛地发展,基于TCN的列车网络已经不能满足列车数据传输业务的需求,列车控制与服务网络TCSN应运而生。针对列车数据传输业务研究了基于综合服务模型的列车通信网络,建立了四类列车业务流量模型,分析了网络分组的加权公平队列调度算法（WFQ）,设计了基于服务分类和带宽分配的加权公平队列调度算法（SCBAWFQ）,并且利用仿真软件对恒定数据流和突发数据流分别在WFQ与SCBAWFQ算法下的时延进行了仿真与分析,仿真结果证明改进算法在降低实时业务流延时方面有很好的效果,SCBAWFQ算法既保持了WFQ算法的公平性又满足实时业务服务质量的需求。     

网络自适应公平分组抽样算法研究

针对SGS(sketch guided sampling)的缺陷,提出了一种网络自适应公平抽样算法.根据抽样分组估计出值流量大小,并依据该值调整抽样比,使之适应于流量变化,从而达到对各种流的公平抽样的效果.对算法的相关性质进行了证明与分析,基于实际互联网数据进行了实验比较,实验结果表明,该算法具有准确性、自适应性、易于工程实现等优点.     

图书馆多媒体业务流的短时公平分组反馈调度方法

研究了一种新的基于短时公平的分组调度算法的问题. 基于短时公平性的分组反馈调度算法改进了WF2Q＋算法在短期内无法为新加入客户端提供公平服务的缺陷,增强了调度算法的适应性和公平性. 在本算法中,调度器中的各个客户端权值能够根据其获得的实际服务量状况在线调整,增强了系统的鲁棒性和自适应性,同时提高了系统实现短期公平性的能力,对各个客户端提供更为公平的服务质量（Quality of Service,QoS）.     

一种Internet上的优先权加权平均数据传输方法

文章基于优先权处理和队列式加权平均流量分配提出一种在Internet上有效地传送带优先权数据的方法,该方法包括两个路由器优先权加权平均算法(PWFQ):单队列记数排序算法(SQSS)和多队列布谷鸟轮换算法(MQRR)。路由器使用PWFQ公平有效地为超流(superflow)分配和调整带宽,并实现了网络阻塞时传输质量的平缓缩减,同时为子流(flow)提供优先权服务,高优先权的子流将被优先服务,从而保证传输的QoS。MQRR还融入RED算法以在阻塞时得到更好的链路利用率、吞吐率和数据流缩减.这种方法融合了Guaranteed服务和Differential服务的优点,算法的计算复杂度不高,实现较易。实验表明这个方法是有效实用的。     

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。     

可编程网络流量公平调度研究综述

网络数据包调度是一个经典的多维决策问题,其核心在于网络设备中如何实时地做出数据包入队和出队的合理决策。在该领域中,流量公平调度是一个备受关注的重要课题。为了保障网络服务等级、缓解链路拥塞以及有效应对网络攻击,快速、公平且通用的调度算法显得至关重要。传统的数据包调度算法实现了公平的带宽分配和流量隔离,但随着软件定义网络(SDN)和可编程网络的出现和发展,灵活且可重构的网络编程方式催生了许多国内外学者提出创新性和实用性的公平调度方案。本文围绕流量公平调度问题,系统地总结了实现公平调度的6种技术路线,并展望了未来的研究方向。     

The proportional fairness scheduling algorithm on multi-classes

In this paper, we study resource management models and algorithms that satisfy multiple performance objects simultaneously. We realize the proportional fairness principle based QoS model, which defines both delay and loss rate requirements of a class, to include fairness, which is important for the integration of multiple service classes. The resulting Proportional Fairness Scheduling model formalizes the goals of the network performance, user's QoS requirement and system fairness and exposes the fundamental tradeoffs between these goals. In particular, it is difficult to simultaneously provide these objects. We propose a novel scheduling algorithm called Proportional Fairness Scheduling (PFS) that approximates the model closely and efficiently. We have implemented the PFS scheduling in Linux. By performing simulation and measurement experiments, we evaluate the delay and loss rate proportional fairness of PFS, and determine the computation overhead.     

Assured forwarding fairness using equation-based packet marking and packet separation

Fairness is one of the important problems in assured forwarding (AF) performance in the differentiated services (DiffServ) framework [An architecture for differentiated services, RFC 2475, IETF, December 1998; A two-bit differentiated services architecture for the Internet, Internet-draft, draft-nichols-diff-svc-arch-02.pdf, IETF, April 1999]. In this paper we present a two-part solution for the fairness problem in AF. The first part is a new packet marking algorithm called equation-based marking (EBM) and is based on the TCP model given by Padhye et al. [Modeling TCP throughput: A simple model and its empirical validation, in: Proceedings of ACM SIGCOMM ’98, October 1998]. EBM is to handle the problems found in other marking schemes regarding fairness among heterogeneous TCP flows through a tight feedback-loop operation and adaptation of the packet marking probability to network conditions. The second part is called packet separation used at routers to handle the fairness between responsive and non-responsive traffic. We evaluate the performance of a packet marker that uses EBM as the marking algorithm using in-depth simulation. We prove, analytically and using simulation, the correctness of the marking algorithm and compare it with other marking schemes for different network scenarios. We also use simulation to show the effectiveness of the packet separation mechanism in solving the fairness problem between responsive and non-responsive traffic. Our evaluation results demonstrate the effectiveness of EBM along with packet separation in providing the required fairness among heterogeneous flows and ensuring protection against non-assured traffic.     

On Sustained QoS Guarantees in Operated IEEE 802.11 Wireless LANs

Most of QoS-capable IEEE 802.11 MAC protocols are unable to deliver sustained quality of service while maintaining high network utilization, particularly under congested network conditions. The problem often resides in the fact that flows belonging to the same service class are assigned the same MAC parameters regardless theirs respective bitrate, which leads to throughput fairness rather than perceived QoS fairness. Harmonizing MAC parameters of traffic classes's flows may further lead to sub-optimal situations since certain network configurations (in terms of per class traffic load) can not be accommodated without reassigning the basic MAC parameters. In this paper, we propose a new cross-layer MAC design featuring a delay-sensitive backoff range adaptation along with a distributed flow admission control. By monitoring both MAC queue dynamics and network conditions, each traffic class reacts based on the degree to which application QoS metrics (delay) are satisfied. Besides, we use a distributed admission control mechanism to accept new flows while protecting the active one. Simulation results show that compared to the enhanced distributed coordination function (EDCA) scheme of 802.11e, our protocol consistently excels, in terms of network utilization, bounded delays, and service-level fairness.     

一种适用于多业务场景的HSDPA分组调度算法

针对HSDPA多业务应用场景,提出一种新的分组调度算法。该分组调度算法在保证每种业务的QoS的同时,兼顾公平性和分组时延限制。在包含流类、交互类以及背景类业务的应用场景里对该算法进行仿真。仿真结果表明,与正比公平和M-LWDF算法相比,该算法能获得更好的系统性能。     

基于WCDMA系统混合业务的新型调度算法

WCDMA系统混合业务下设计调度算法要考虑信道条件,要区分业务保证用户的QoS要求,避免用户“饥饿”现象,同时也要尽可能提高整个系统的吞吐量和调度的公平性。由此,在比例公平调度算法（PFS）基础上基于C/I、QoS、饥饿权重提出区分业务类型的比例公平分组调度算法（CQSSD－PFS）,同时引入实时业务和系统容量补偿模型,仿真结果表明可有效确保各类业务之间的短期、长期公平性和较高的系统吞吐量。     

基于速率预测的三色标记算法

提出了一种适用于比例区分服务的数据包标记算法——基于速率预测的三色标记算法(Rate Prediction Marker, RPM)。RPM算法基于在线流量预测算法,对DiffServ网络中经过分类器划分的网络流或者进入标记器的网络流进行提前1期流量预测,根据预测结果以及历史流量的均值进行加权后的结果对数据包进行标记。当源端可能进入TCP的拥塞恢复阶段时,按比例将网络中的可用带宽分配给服务聚集流,从而提高网络带宽的利用率。仿真和实验结果表明,RPM算法与现有的算法相比在目标速率影响和带宽吞吐量上具有更好的性能,从而获得了很好的公平性和带宽利用率。     

Two efficient packet aggregation mechanisms and QoS support in a slotted dual bus optical ring network

In this paper, a novel approach for efficiently supporting IP packets directly into a slotted optical wavelength-division-multiplexing (WDM) layer with several quality of service (QoS) requirements is presented and analyzed. The approach is based on two main features. First, an aggregation cycle is performed at fixed time intervals by assembling several IP packets into a single macro-packet of fixed size, called an aggregate packet. Second, since IP packets have variable size, the aggregation process may allow or not the segmentation of an IP packet if it does not fit into the remaining gap in the aggregate packet. As a key element of our proposition, an efficient QoS support access mechanism is presented. The new QoS control performs aggregation in a loop manner by always beginning the aggregation cycle with the highest priority class. The aggregation cycle ends if the aggregate packet cannot accommodate more IP packets, or if the lowest priority class is reached. We introduce two analytical models that allow us to evaluate the effectiveness of the aggregation technique with and without segmentation. On the other hand, a third analytical model is presented to analyze the standard case (where no aggregation is performed), and comparisons between the three models are carried out. The aggregation models are validated by simulations, and the effect of self-similarity is also analyzed. The application of the proposed approach takes place in a slotted dual bus optical ring network (SDBORN), where we prove that a good fairness and high bandwidth efficiency are achieved, and that only two QoS classes (real-time and non-real-time classes) at the access interface (IP domain) are sufficient in order to fulfill the strict delay requirements of real-time data traffic.     

Hardware design and implementation of packet fair queuing algorithms for the quality of service support in the high-speed internet

The increasing amount of real-time traffic carried over the Internet requires end-to-end quality of service (QoS) support. To this end, the QoS Schedulers, that are implemented in routers, assign the available bandwidth resources to packet flows according to their respective allocated rates. Packet Fair Queuing (PFQ) schedulers can provide fair service and low end-to-end delay bound to the traffic flows. However, they have higher implementation complexity compared to other algorithms, because of the requirements of tracking the system state, and searching for the packet to get service among all flows, that are queued at the outgoing interface. QoS scheduling is a data plane functionality, which requires hardware implementation for high speed router interfaces. The previous works on hardware implementation of PFQ schedulers are specific to certain algorithms, and they do not provide any results on real hardware platforms. In this paper, we present a general hardware design framework for PFQ schedulers, and apply this framework to the WF²Q+ PFQ algorithm to demonstrate its properties. We carry out the entire implementation of the WF²Q+ algorithm on an FPGA, and evaluate its performance with real traffic flows. In addition, we implement WFQ as a second PFQ algorithm to demonstrate the generality of the framework.     

数据中心网络中基于传输速率分配算法的TCP协议

传输控制协议(Transmission Control Protocol,TCP)是数据中心网络中常用的传输协议。然而,同一个网络环境下,由于TCP协议的公平共享原则,TCP无法保障不同优先级业务的服务质量。针对该问题,提出了基于传输速率分配算法的TCP(Transmit Rate Allocation based TCP,TRA-TCP)。汇聚节点实时监测记录不同优先级业务的数据传输速率,并为不同优先级的业务流分配不同的传输速率,以保障高优先级业务的QoS。实验表明,与已有协议相比,TRA-TCP协议最高能够将高优先级业务的吞吐量提升50%,并且将高优先级业务的时延保持在0.1秒以下。     

网络传输控制的综合性能评价标准

在网络传输控制策略和算法的设计中，性能评价的标准是一个关键问题，不同的评价标准将导致不同的控制策略和算法设计。由于网络传输控制策略有着多方面性能的要求，如何同时满足多个性能目标是当前的研究难点，该文基于网络传输控制模型提出了一套对网络传输控制进行综合性能评价的有效标准，该标准综合考虑了网络整体性能、用户QoS要求和系统公平性等多维目标，作者对该标准进行了详细的讨论和分析，文中的综合性能标准可以广泛用于网络传输控制策略的性能评价和改进。