Web服务器集群系统QoWS研究

请求负载的增加常常导致Web服务器系统性能降低,用户期望的服务质量得不到保证,这是服务级Web系统所面临和必须解决的问题。文章提出了一种Web服务器集群环境下的负载分配策略,通过对用户请求分类、将不同类别的请求进行响应性能隔离、优先为高级别请求提供服务以及请求许可控制等手段,对不同类别的Web请求提供不同质量的服务,保证了服务级用户的服务质量。同时采用最迟分配原则,改善系统的负载均衡能力,缩短系统平均响应时间。最后通过仿真实验,验证了该策略的正确性和有效性。     

跨域流媒体边缘云资源调整策略

随着云计算技术的成熟,跨域边缘云模式下的流媒体服务正逐渐兴起。但流媒体相关的用户请求随时间波动较大,边缘云需要动态调整需租赁的云资源来同时保证用户服务质量和资源利用率。文中提出的云资源调整策略综合考虑了跨域流媒体边缘云的资源消耗模型、相关用户服务质量指标的量化以及跨域转发用户请求对系统服务的影响,通过系统资源调整阶段和子云资源调整阶段策略的合理协调,在保证用户服务质量的同时节约了系统总体云资源的租赁代价,同时仿真结果表明文中策略能够取得上述优化效果。     

支持高负载的短信服务软件性能研究

目前普遍应用的在确定资源环境下的FCFS短信服务调度机制在处理请求过载的情况下难以保证服务质量,本文提出的系统自适应组网以及根据获益分析动态调整资源的模型,实验证明了对于提高服务器服务质量的有效性.     

支持随机服务请求的云虚拟机按需物理资源分配方法

本文针对云平台按负载峰值需求配置处理机资源、提供单一的服务应用和资源需求动态变化导致资源利用率低下的问题,采用云虚拟机中心来同时提供多种服务应用.利用灰色波形预测算法对未来时间段内到达虚拟机的服务请求量进行预测,给出兼顾资源需求和服务优先等级的虚拟机服务效用函数,以最大化物理机的服务效用值为目标,为物理机内的各虚拟机动态配置物理资源.通过同类虚拟机间的全局负载均衡和多次物理机内各虚拟机的物理资源再分配,进一步增加服务请求量较大的相应类型的虚拟机的物理资源分配量.最后,给出了虚拟机中心基于灰色波形预测的按需资源分配算法ODRGWF.模拟实验表明所提算法能够有效提高云平台中处理机的资源利用率,对提高用户请求完成率以及服务质量都具有实际意义.     

支持高负载的短信服务软件性能研究

目前普遍应用的在确定资源环境下的FCFS短信服务调度机制在处理请求过载的情况下难以保证服务质量．本文提出的系统自适应组网以及根据获益分析动态调整资源的模型．实验证明了对于提高服务器服务质量的有效性．     

基于QoS的磁盘调度策略

随着视频点播、视频会议、视频监控、数字图书馆等流媒体应用的普及，流媒体服务器存储资源管理成为制约服务质量的瓶颈之一。根据多媒体服务器的性能要求，提出了一种支持QoS的磁盘调度策略。它由三个主要部分组成：探测模块、负载监测模块和自适应管理模块。探测模块，负责判断当前的资源情况能否满足服务请求；自适应模块，根据负载监删模块检测到的负载变化情况，动态调整服务周期在实时请求和尽力服务请求之间的分配。实验表明此磁盘调度策略能在保证实时请求无抖动执行的同时，明显减少了非实时请求的响应时间。     

基于语义的Web服务发现算法

传统的Web服务发现只是简单的基于关键字的语法匹配,查询得到的服务往往不是用户想要的.在基于接口的Web服务发现的基础上,改进了Web服务描述模型,增加了服务质量(QoS),提出了分步过滤匹配算法.先通过服务类别过滤器进行语义过滤筛选,去除不相关的Web服务,然后通过服务相似度度量候选服务和请求服务之间的相似程度.候选服务和请求服务之间的相似度是通过服务功能相似度和服务质量相似度两个方面进行综合评估的.最后,通过实验证明了该匹配算法的可行性和有效性.     

支持QoS确保的存储服务器服务资源分配算法

在电子商务、工业制造领域中,具有海量存储与高I/O吞吐能力的数据存储服务器得到了广泛应用。数据存储服务器提供QoS支持对应用需求而言很重要,但是实践中却很少有数据存储服务器提供了QoS支持。提出了一种支持服务质量区分并对高优先级用户提供服务质量保证的存储服务区服务资源分配算法,由于对高优先级用户请求与低优先级用户请求采用了可变服务质量区分因子,因而算法在提供服务优先级区分与确保高优先级请求服务质量的同时,减小了低优先级请求的请求丢弃率,同时最大化了服务资源利用率。     

异构无线网络多网资源优化管理研究

针对异构无线网络多网协同的特点,从分析多个无线网络共存的资源管理优化体制构建思想出发,建立了新的异构无线网络资源统一管理优化模型,实现了协同信息的控制和管理,同时保证了异构数据呼叫业务的服务质量,解决了多网间资源管理优化问题。首先,该模型在对呼叫服务请求做优化决策时,不仅考虑了本网络服务域的可用资源、服务请求的速率以及本系统的长期收益,同时也考虑了其他网络服务域的整体长期收益;其次,通过对所提出的基于异构无线网络多网资源优化管理模型的性能进行理论分析,得到其重要服务质量参数——新呼叫阻塞率;最后,通过仿真比较可以看出,通过该模型获得的优化决策策略能充分利用异构无线网络中各个网络域的资源,不仅提高了资源的利用率,而且在提高网络整体长期收益的同时,也保证了移动服务的服务质量。与资源完全共享算法相比,本方法降低了新呼叫阻塞率。理论分析和实验证明了异构无线网络资源域间资源优化管理方法的有效性、适应性。     

基于服务总线的智能电视资源管理框架

针对智能电视系统中多任务运行时面临的应用服务质量(QoS)保障和资源管控问题,提出基于服务总线架构的智能电视系统资源管理框架,其中资源监测模块监测系统中应用的资源消耗;资源规划模块对全局资源进行规划,对资源请求进行调度;资源执行模块管控应用进程资源请求,并分配资源.框架对系统中各类资源提供管控机制,根据应用的QoS和优先级对应用进行动态规划和调度,保障了资源的安全性和应用的QoS.     

Semantic-enabled CARE Resource Broker (SeCRB) for managing grid and cloud environment

Grid computing is mainly helpful for executing high-performance computing applications. However, conventional grid resources sometimes fail to offer a dynamic application execution environment and this increases the rate at which the job requests of users are rejected. Integrating emerging virtualization technologies in grid and cloud computing facilitates the provision of dynamic virtual resources in the required execution environment. Resource brokers play a significant role in managing grid and cloud resources as well as identifying potential resources that satisfy users’ application requests. This research paper proposes a semantic-enabled CARE Resource Broker (SeCRB) that provides a common framework to describe grid and cloud resources, and to discover them in an intelligent manner by considering software, hardware and quality of service (QoS) requirements. The proposed semantic resource discovery mechanism classifies the resources into three categories viz., exact, high-similarity subsume and high-similarity plug-in regions. To achieve the necessary user QoS requirements, we have included a service level agreement (SLA) negotiation mechanism that pairs users’ QoS requirements with matching resources to guarantee the execution of applications, and to achieve the desired QoS of users. Finally, we have implemented the QoS-based resource scheduling mechanism that selects the resources from the SLA negotiation accepted list in an optimal manner. The proposed work is simulated and evaluated by submitting real-world bio-informatics and image processing application for various test cases. The result of the experiment shows that for jobs submitted to the resource broker, job rejection rate is reduced while job success and scheduling rates are increased, thus making the resource management system more efficient.     

具有QoS保障功能的服务网格资源映射策略

针对网格资源映射对用户的服务质量(QoS)偏好考虑不足的问题,对保障多维QoS的网格资源映射算法进行研究,从服务网格资源的多维QoS属性分析入手,在满足用户全局约束的前提下,根据服务中各子任务的QoS约束筛选出符合要求的网格资源,并给出合理的映射结果,提出一种网格资源映射算法——QoS-Sufferage算法。利用GridSim平台进行仿真比较,结果验证了算法的有效性。     

基于用户会话的Web服务器应用软件的QoS技术分析

传统的Web服务器应用软件对客户的请求不加识别和区分，接收到一个请求便立即进行处理。因此，这种“一视同仁”的服务无法为高优先级的请求提供Web QOS保证。通过改进应用软件，Web服务器可以为不同的客户或请求提供Web QOS。其主要方法是将客户的HTTP请求进行分类，并且实现优先化调度、接纳控制、资源分配等机制。本文介绍了基于用户会话的Web服务器应用软件的QoS技术，并指出其中存在的缺陷。     

Analyzing the performance of deferred reservations

This paper studies the performance of deferred resource reservation in data networks. Conventional resource reservation protocols, such as PNNI and RSVP adopt an all-or-nothing approach, where partially acquired resources must be released if resources are not available at all links on the chosen path. During periods of high network load, this leads users to retry requests repeatedly, adding control traffic at exactly the time when the network’s capacity to process that control traffic is exhausted. Deferred REServation (DRES) can significantly improve performance by reducing the overall call rejection probability, allowing more traffic to be carried, using the same resources. Call admissibility is increased by deferring requests at routers for a limited period of time until resources become available. The paper includes analytical models that predict the blocking probability on a DRES multiplexor and on a multi-hop path, and simulation results for substantial network configurations, using several QoS routing methods. The results show that DRES can provide substantial performance gains over traditional reservations (upto 50% with QoS routing enabled and upto an order of magnitude for non-QoS traditional routing).     

基于MDP支持弹性服务质量的接入控制

在网络服务系统中,满足业务请求的服务质量需求是系统要解决的主要问题之一。接入控制方法和资源分配策略常用来保证业务的服务质量要求。本文基于Markov决策过程(MDP)对视频点播(VOD)系统进行建模,同时考虑了弹性服务质量这一机制。弹性服务质量可以用一个QoS的需求范围来体现。策略梯度算法常用来解决MDP问题,它能够以比较好的速度收敛到最优解。通过算法实例对本文的接入控制方法进行性能分析,发现所采用的方法相对于一般的完全接入策略具有较优的性能。     

Cost-based admission control for Internet Commerce QoS enhancement

In many e-commerce systems, preserving Quality of Service (QoS) is crucial to keep a competitive edge. Poor QoS translates into poor system resource utilisation, customer dissatisfaction and profit loss. In this paper, a cost-based admission control (CBAC) approach is described which is a novel approach to preserve QoS in Internet Commerce systems. CBAC is a dynamic mechanism which uses a congestion control technique to maintain QoS while the system is online. Rather than rejecting customer requests in a high-load situation, a discount-charge model which is sensitive to system current load and navigational structure is used to encourage customers to postpone their requests. A scheduling mechanism with load forecasting is used to schedule user requests in more lightly loaded time periods. Experimental results showed that the use of CBAC at high load achieves higher profit, better utilisation of system resources and service times competitive with those which are achievable during lightly loaded periods. Throughput is sustained at reasonable levels and request failure at high load is dramatically reduced.     

A Resource Reservation Scheme for Synchronized Distributed Multimedia Sessions

Guarantees of services in a networked environment are provided by the proper allocation and scheduling of network and system resources. A lot of research in packet scheduling, QoS routing, traffic multiplexing, etc. has been aimed at providing deterministic or statistical service guarantees, while utilizing resources efficiently. In this paper, we propose a resource reservation scheme for a class of multimedia presentations. We characterize this class of multimedia presentations as synchronized distributed multimedia sessions, which we believe are important components of many multimedia applications. In addition to multimedia presentations, the reservation scheme applies to applications with synchronized resource requirements. Based on resource inquiry and interval analysis, the scheme is also able to find feasible resource allocation schedules for resource reservation requests. Built upon a layer of resource abstraction, the scheme suits well with today's heterogeneous network environment.     

移动WiMAX网络中的VoIP调度机制

移动微波存取全球互通(WiMAX)网络使用了5种调度机制来保证服务质量,其中的3种被设计用于实时性业务。但是,这3种调度机制都缺乏公平性。在资源不足的时候,通过丢弃新用户的请求来保证旧用户的服务质量(QoS)。为此,针对WiMAX中的因特网语音(VoIP)服务提出了一种基于优先权的新调度机制。该机制中,不同用户的业务请求将被赋予不同的优先权。新旧用户同时请求资源时,新用户的请求拥有更高的优先权;资源分配中心再根据优先权的高低为用户分配资源,从而在最大限度上保证了资源分配的公平性。仿真结果显示,新调度机制可以将网络中的因特网语音服务的连接数和总吞吐量分别提高15%和11%左右。     

QoS and preemption aware scheduling in federated and virtualized Grid computing environments

Resource provisioning is one of the challenges in federated Grid environments. In these environments each Grid serves requests from external users along with local users. Recently, this resource provisioning is performed in the form of Virtual Machines (VMs). The problem arises when there are insufficient resources for local users to be served. The problem gets complicated further when external requests have different QoS requirements. Serving local users could be solved by preempting VMs from external users which impose overheads on the system. Therefore, the question is how the number of VM preemptions in a Grid can be minimized. Additionally, how we can decrease the likelihood of preemption for requests with more QoS requirements. We propose a scheduling policy in InterGrid, as a federated Grid, which reduces the number of VM preemptions and dispatches external requests in a way that fewer requests with QoS constraints get affected by preemption. Extensive simulation results indicate that the number of VM preemptions is decreased at least by 60%, particularly, for requests with more QoS requirements.     

Cross-layer optimization policy for QoS scheduling in computational grid

This paper presents a cross-layer quality of service (QoS) optimization policy for computational grid. Efficient QoS management is critical for computational grid to meet heterogeneity and dynamics of resources and users’ requirements. There are different QoS metrics at different layers of computational grid. To improve perceived QoS by end users over computational grid, QoS supports can be addressed in different layers, including application layer, collective layer, fabric layer and so forth. The paper tackles cross-layer grid QoS optimization as optimization decomposition, each layer corresponds to a decomposed subproblem. The proposed policy produces an optimal set of grid resources, service compositions and user's payments at the fabric layer, collective layer and application layer respectively to maximize global grid QoS. The cross-layer optimization problem decomposes into three subproblems: grid resource allocation problem, service composing and user satisfaction degree maximization problem, all of which interact through the optimal variables for capacities of grid resources and service demand. In order to coordinate the subproblems, cross-layer QoS feedback mechanism is established to ensure different layer interactions. The simulations are conducted to validate the efficiency of the proposed policy.