一种基于QoS的Web服务选择模型

服务质量是面向服务应用中考虑的重要因素之一.对现有的SOA标准模型进行了扩展,提出了一种基于QoS的Web服务选择模型.模型中新增实体提供对QoS的支持,采集服务提供者和服务消费者的QoS反馈信息,以此评估Web服务的质量.在服务选择时,该模型在考虑QoS评价排名的同时,运用滑动窗口策略,分摊系统负载和避免负载抖动现象.仿真实验结果显示了该思想的有效性.     

基于混沌预测的IP QoS模型与机制

利用混沌相关理论对具有综合业务应用的IP网流量进行了混沌特性与预测分析，提出了基于混沌预测的IP QoS实现模型与算法。OPNET的网络仿真实验表明，与传统的静态QoS参数配置方法和基于测量的QoS设置方法比较，该模型及方法在网络重负载环境下使各业务的QoS性能指标得到有效改善。     

基于非确定性推理的网构软件服务质量动态评估方法

提出了网构软件环境下一种基于非确定性推理的构件服务质量动态评估方法.该方法基于贝叶斯网络,其主要特点在于考虑了用户对构件的QoS需求,可以预测在用户多种QoS需求下采用分级策略的构件服务能力,支持评估模型的动态更新,提高了评估结果的准确性.在自主开发的服务协同总线(Once-SCB)平台上进行了应用与验证,结果表明,该评估模型准确、有效,可以在用户多种QoS需求下为其选择最为合适的构件.     

基于支持区分服务带宽预测的移动自组网QoS路由协议

已有移动自组网QoS路由协议的研究假设节点的可用带宽信息已知,主要侧重在协议的寻路算法和如何降低网络开销.而已有的带宽预测方法没有考虑通信的业务类型,预测结果不够准确.本文提出一种支持区分服务的可用带宽预测模型,该模型不仅考虑了节点之间信道争用的影响,而且从具有不同优先级的业务角度出发对可用带宽进行预测.在该模型的基础上,我们进一步对AODV协议进行扩展,使其支持QoS特性.仿真结果表明本文带宽预测模型能有效地对可用带宽进行预测,扩展后的AODV协议也可提供较好的QoS性能.     

面向Web Server的QoS自适应控制鲁棒性研究

给出了一种面向Web服务器的自适应节模型和基于卡尔曼滤波的会话流自适应控制算法，并在此基础上提出了一种Web QoS自适应控制机制，利用在线系统辨识实现动态的连接调度和进程重新分配，从而为不同的服务类提供相应的QoS保证。采用全论域范围内基于离散型卡尔曼滤波方法进行QoS参数的最优预测。仿真结果表明，该自适应Web服务器的QoS控制机制可以实现鲁棒的相对QoS保证，并且能够确保稳定性。     

无线传感器网络满足QoS带宽需求 的能量最优路由方案

有效使用片上受限资源以保持最长的生命周期是无线传感器网络的核心问题.QoS路由技术解决了无线传感器网络要求支持多种业务的差别服务和全网范围的资源有效利用的问题.本文提出了一种可以满足QoS带宽需求的能量最优路由发现方法.该方法构建了节点选择模型、能量评价模型和节点能耗权重模型,使用遗传算法利用可用节点集合建立满足QoS带宽需求的能量最优路由.利用Markov链证明该算法是可收敛并且是以指数速度概率强收敛的.另外,通过实验仿真与分析,给出了本文遗传算法的控制参数的选择区间,实验显示本文提出的满足QoS带宽需求的路由发现方法对无线传感器网络具有更好的适应性和更长的网络寿命.     

联合无线资源管理技术的改进型垂直切换算法

针对移动主机在垂直切换过程中无线资源的合理分配问题,基于通用移动通信系统(UMTS)和无线局域网(WLAN)构建的无线异构网络环境,按照不同业务的服务质量(QoS)优先级,提出一种联合带宽借用、负载均衡机制的新型垂直切换算法;建立基于Matlab的性能评估仿真平台,对新呼阻塞率、掉话率进行分析。结果表明,该算法可以在维持较小阻塞率的情况下,有效减少掉话率,保证QoS需求高的话音业务取得很好的服务质量。     

基于服务模型的定价机制研究综述

近几年,随着高带宽需求、高QoS要求应用的不断涌现,人们开始越来越多的关注QoS及网络效率问题,根据不同业务对QoS需求的不同可以将网络服务类型分为尽力而为服务和满足QoS要求的服务,因而ISP在制定价格时必须考虑网络的服务类型,制定与服务模型相符合的定价机制。针对多钟网络服务模型,考虑现有基于服务模型的定价研究,并进行分析与评价。     

Web 服务器的鲁棒建模和过载控制

给出了一种Web 服务器的建模方法，说明了如何用控制理论管理不可预测的服务器负载。Web 服务器可以被仿真为一个多容器系统。该鲁棒Web 服务器模型适用于未知的负载干扰和不确定的匹配模型。过载控制技术基于自适应允许控制取得时间保证，用一个完整参数变化模型和大的过载来评估模型的性能。     

单向Ad_Hoc移动网络的QoS路由协议

针对Ad_Hoc移动网络的特点,提出了一种支持单向Ad_Hoc移动网络,并且具有QoS控制的路由协议QRUA,该协议充分考虑了网络存在的单向链路,利用邻接主机之间的上游主机表UT来选择满足延时和带宽要求的路由,从而可以适应特定环境下单向Ad_Hoc移动网络的QoS应用需求.模拟仿真说明,QRUA协议不但支持单向链路,同时在路由负载以及包传输率等方面具有一定的优势.     

TPC-W e-commerce benchmark evaluation

Correctly interpreting benchmark results requires a basic knowledge of the synthetic workload the benchmark uses to determine how well it represents diverse e-commerce applications' real-world workloads. Factors that influence these results include the characteristics of the system under test, the procedures used to execute the tests, and the performance metrics the benchmark generates. TPC-W performs server evaluation in a controlled Internet e-commerce environment that simulates the activities of a business-oriented transactional Web server. The authors used experimental results from their TPC-W implementation to assess the benchmark's behavior, including its granularity and sensitivity to changes in workload and system parameters.     

Proactive planning of bandwidth resource using simulation-based what-if predictions forWeb services in the cloud

Resource planning is becoming an increasingly important and timely problem for cloud users.As more Web services are moved to the cloud,minimizing network usage is often a key driver of cost control.Most existing approaches focus on resources such as CPU,memory,and disk I/O.In particular,CPU receives the most attention from researchers,but the bandwidth is somehow neglected.It is challenging to predict the network throughput of modem Web services,due to the factors of diverse and complex response,evolving Web services,and complex network transportation.In this paper,we propose a methodology of what-if analysis,named Log2Sim,to plan the bandwidth resource of Web services.Log2Sim uses a lightweight workload model to describe user behavior,an automated mining approach to obtain characteristics of workloads and responses from massive Web logs,and traffic-aware simulations to predict the impact on the bandwidth consumption and the response time in changing contexts.We use a real-life Web system and a classic benchmark to evaluate Log2Sim in multiple scenarios.The evaluation result shows that Log2Sim has good performance in the prediction of bandwidth consumption.The average relative error is 2%for the benchmark and 8% for the real-life system.As for the response time,Log2Sim cannot produce accurate predictions for every single service request,but the simulation results always show similar trends on average response time with the increase of workloads in different changing contexts.It can provide sufficient information for the system administrator in proactive bandwidth planning.     

基于马尔科夫链的联合呼叫接入控制算法

异构网络的接入策略与网络资源管理效率紧密相关;同时,网络复杂性与网络资源竞争性直接影响到用户服务质量。针对异构网络接入控制存在的切换掉话率和呼叫阻塞率高、资源利用率低等问题,提出了基于马尔科夫链的联合呼叫接入控制算法。接入控制算法为切换呼叫业务、实时业务动态地预留了一定的带宽资源,根据不同业务设置带宽降级因子来决定是否释放带宽;同时,根据用户偏好和不同业务的QoS要求,构建了呼叫接入控制效用函数,利用马尔科夫链进行了建模分析。仿真表明,算法提高了网络资源利用率,降低了系统复杂度,满足了各类业务的QoS要求。     

Workload-aware anomaly detection for Web applications

The failure of Web applications often affects a large population of customers, and leads to severe economic loss. Anomaly detection is essential for improving the reliability of Web applications. Current approaches model correlations among metrics, and detect anomalies when the correlations are broken. However, dynamic workloads cause the metric correlations to change over time. Moreover, modeling various metric correlations are difficult in complex Web applications. This paper addresses these problems and proposes an online anomaly detection approach for Web applications. We present an incremental clustering algorithm for training workload patterns online, and employ the local outlier factor (LOF) in the recognized workload pattern to detect anomalies. In addition, we locate the anomalous metrics with the Student's t-test method. We evaluated our approach on a testbed running the TPC-W industry-standard benchmark. The experimental results show that our approach is able to (1) capture workload fluctuations accurately, (2) detect typical faults effectively and (3) has advantages over two contemporary ones in accuracy.     

Bench4Q:一种面向服务质量的电子商务测试基准设计与实现

作为电子商务系统的基础运行平台,应用服务器提供的服务质量是关注焦点,然而目前主流的电子商务测试基准如TPC-W,主要关注性能度量,缺乏针对电子商务服务质量需求的设计,使得其难以准确地评价应用服务器提供的服务质量。提出了一种面向服务质量的电子商务测试基准Bench4Q,它在模拟负载仿真、度量分析等多个方面对TPC-W进行了扩展,并通过对典型的应用服务器的测试展示了Bench4Q的设计特征。     

面向应用服务级目标的虚拟化资源管理

在虚拟环境中实现应用服务级目标,是当前数据中心系统管理的关键问题之一.解决该问题有两个方面的要求:一方面,在虚拟化层次和范围内,能够动态和分布式地按需调整虚拟机资源分配;另一方面,在虚拟化范围之外,能够控制由于虚拟机对非虚拟化资源的竞争所导致的性能干扰,实现虚拟机性能隔离.然而,已有工作不适用于虚拟化数据中心场景.提出一种面向应用服务级目标的虚拟化资源管理方法.首先,该方法基于反馈控制理论,通过动态调整虚拟机资源分配来实现每个应用的服务器目标;同时,还设计了一个两层结构的自适应机制,使得应用模型能够动态地捕捉虚拟机资源分配与应用性能的时变非线性关系;最后,该方法通过仲裁不同应用的资源分配请求来控制虚拟机在非虚拟化资源上的竞争干扰.实验在基于Xen的机群环境中检验了该方法在RUBiS系统和TPC-W基准上的效果.实验结果显示,该方法的应用服务级目标实现率比两种对比方法平均高29.2%,而应用服务级目标平均偏离率比它们平均低50.1%.另一方面,当RUBiS系统和TPC-W基准竞争非虚拟化的磁盘I/O资源时,该方法通过抑制TPC-W基准28.7%的处理器资源需求来优先满足RUBiS系统的磁盘I/O需求.     

Extending Proxy Caching Capability: Issues and Performance

Proxy caching is an effective approach to reduce the response latency to client requests, web server load, and network traffic. Recently there has been a major shift in the usage of the Web. Emerging web applications require increasing amount of server-side processing. Current proxy protocols do not support caching and execution of web processing units. In this paper, we present a weblet environment, in which, processing units on web servers are implemented as weblets. These weblets can migrate from web servers to proxy servers to perform required computation and provide faster responses. Weblet engine is developed to provide the execution environment on proxy servers as well as web servers to facilitate uniform weblet execution. We have conducted thorough experimental studies to investigate the performance of the weblet approach. We modify the industrial standard e-commerce benchmark TPC-W to fit the weblet model and use its workload model for performance comparisons. The experimental results show that the weblet environment significantly improves system performance in terms of client response latency, web server throughput, and workload. Our prototype weblet system also demonstrates the feasibility of integrating weblet environment with current web/proxy infrastructure.     

SoPHy+: Programming model and software platform for hybrid resource management of many-core accelerators

As demand of higher computing power is steadily increasing, it becomes popular to equip a many-core accelerator in a computer system to run concurrent applications. Efficient management of compute resources in such a system is challenging because various factors such as workload variation, QoS requirement change, and hardware failure may cause dynamic change in system status. Recently, a variety of resource management techniques for many-core accelerators have been proposed. They are usually tailored for a specific target architecture. In this paper, we present SoPHy+, which supports various types of many-core accelerators, based on a hybrid resource management technique. SoPHy+ provides a seamless design flow from programming front-end, which generates dataflow-style function codes automatically from the task specification, to run-time environment, which adaptively manages compute resources for concurrent applications in response to system status change. SoPHy+ has been implemented on two different many-core architectures: the Intel Xeon Phi coprocessor and an Epiphany-like NoC virtual prototype. Experimental results prove that SoPHy+ is capable of adapting to the run-time workload variation effectively with affordable overhead of run-time resource management.     

混合网络模型中的QoS路由算法

QoS路由为具有QoS要求的应用寻找满足条件的网络路径,同时优化网络的资源利用率.IntServ/DiffServ混合网络模型很好的结合了IntServ网络每一流的处理能力和DiffServ网络良好的可扩展性的优点.本文提出了一种在这种混合网络模型中提供带宽一延时保证服务的QoS路由算法,对于在网络中传送具有带宽一延时要求的应用服务是一个可行的解决方案.通过仿真实验,验证了算法的有效性.     

一种收益敏感的虚拟资源按需提供方法

基于虚拟机的资源重配置操作具有耗时长并伴随性能衰减的特点。已有的 Cost-Oblivious 和 Cost-Aware方法在面对Internet突变负载时存在因经常执行资源重配置操作而导致频繁QoS违约的不足。提出了一种收益敏感(benefit-aware)的资源按需提供方法。该方法首先考虑了 Web 应用在配置稳定期内的 QoS 获益,并以此构建收益函数;然后,以收益率最大化原则作为资源重配置策略选择的依据。实验结果表明,该方法与Cost-Oblivious方法相比最多能节约25%的资源成本,而与Cost-Aware方法相比则能有效减少Web应用在突变负载下的QoS违约次数。