Optimal precomputation for mapping service level agreements in grid computing

A complicated task running on the grid system is usually made up of many services, each of which typically offers a better service quality at a higher cost. Mapping service level agreements (SLAs) optimally is to find the most appropriate quality level for each service such that the overall SLA of a task is achieved at the minimum cost. This paper considers mapping the execution time SLA in the case of the discrete cost function, which is an NP-hard problem. Due to the high computation of mapping SLAs, we propose a precomputation scheme that makes the selection of each individual service level in advance for every possible SLA requirement, which can reduce the request response time greatly. We use a (1+ε)-approximation method, whose solution for any time bound is at most (1+ε) times of the optimal cost. Simulation results demonstrate the superiority of our method compared with others.     

国家电网边缘计算应用安全风险评估研究

依据国家网络安全等级保护与风险评估系列标准以及电力信息系统特点,提出国家电网边缘计算应用安全的风险评估模型,然后采用漏洞扫描工具AWVS、AppScan分别对集成最新安全漏洞的开源Web应用靶机软件BWAPP进行安全漏洞评测与风险评估实验,再运用模糊层次分析法对Web应用安全进行综合安全评价。针对应用程序的安全检测实验结果整理安全评估数据,实现对国家电网边缘计算应用安全风险评估的实例化验证。     

Probabilistic optimal solution assessment for DCOPs

Distributed Constraint Optimization Problems (DCOPs) are widely used in Multi-Agent Systems for coordination and scheduling. The present paper proposes a heuristic algorithm that uses probabilistic assessment of the optimal solution in order to quickly find a solution that is not far from the optimal one. The heuristic assessment uses two passes by the agents to produce a high-quality solution. Extensive performance evaluation demonstrates that the solution of the proposed probabilistic assessment algorithm is indeed very close to the optimum, on smaller problems where this could be measured. In larger set-ups, the quality of the solution is demonstrated relatively to standard incomplete search algorithms.     

Security service level agreements for outsourced security functions

This article looks at the areas that should be covered in SLAs with regard to information security, and how they can be monitored.     

Conformance analysis in networks with service level agreements

To achieve some level of Quality of Service (QoS) assurance, a network usually has Service Level Agreements (SLAs) with its users and neighboring domains, which describe the QoS level that the service provider is committed to provide, and the specification of traffic that users or neighboring domains are allowed to send. An interesting and important question arises as to whether a flow is still conformant to its original traffic specification after crossing the network since it may interact with other flows within the network. In this paper, we study analytically the extent to which a flow and an aggregate of flows become non-conformant through an analysis of the stochastic burstiness increase of flows after crossing a per-flow scheduling network and an aggregate scheduling network . The stochastic behavior of a server in aggregate scheduling networks is also studied to determine the conformance deterioration of individual flows, which provides the theoretical conformance deterioration bound and provides useful results for conformance analysis in an aggregate scheduling network with general topology. Our theoretical results are verified by extensive simulations.     

Brokering of risk‐aware service level agreements in grids

Service level agreements (SLAs) are facilitators for widening the commercial uptake of Grid technology. They provide explicit statements of expectation and obligation between service consumers and providers. However, without the ability to assess the probability that an SLA might fail, commercial uptake will be restricted, since neither party will be willing to agree. Therefore, risk assessment mechanisms are critical to increase confidence in Grid technology usage within the commercial sector. This paper presents an SLA brokering mechanism with risk assessment support, which evaluates the probability of SLA failure. WS‐Agreement and risk metrics are used to facilitate SLA creation between service consumers and providers within a typical Grid resource usage scenario. An evaluation is conducted to examine risk models, the performance of the broker's implementation as well as a comparison of its capabilities against similar SLA‐based solutions from the literature. Copyright © 2011 John Wiley & Sons, Ltd.     

基于服务交换的网格资源分配模型

在以服务为核心的网格计算体系结构中,为了实现信任域之间安全任务调度,服务和用户被赋予信任度标签,利用置信度策略成为解决网格计算资源调度安全的一种手段。基于面向服务体系结构,提出了一种服务资源交换协商的参考模型,来解决跨信任域的服务请求和响应问题。文中首先列举了相关的概念,给出参考模型结构,阐述了跨信任域的服务交换协商安全步骤,最后指出了该参考模型中面临的两个重要问题,为进一步研究基于服务交换的网格服务资源分配模型设定方向。     

Managing service level agreements in Premium IP networks: a business-oriented approach

This paper presents a market-enabling framework where users, content providers and network operators can interact in the seamless, transparent sale and delivery of a wide range of services. The framework allows for dynamic creation, configuration and delivery of services with quality assurance, via automated management of Service Level Agreements (SLAs). We propose an approach relying on a systemic treatment of business, service and network layer issues, which translates into a layered architecture where components belonging to different levels interact on the basis of a mediation paradigm. We use mediation as a generic term for a combination of negotiation, brokerage and state notification, jointly concurring to the realization of the entire life-cycle of a service.     

基于证据推理的云计算服务适应性评估

针对云计算服务模式尽管对中小型企业吸引力巨大,但由于受到安全、技术、管理等方面的限制并不是都能适用,企业需要根据自身实际需要作出判断的问题,提出了一个云计算服务适应性评估指标体系。该体系从安全与风险、数据、服务、资源、经济五个维度来分析云计算服务的适应性问题,并利用证据推理方法对实际问题进行建模分析,验证了评估指标体系的有效性与合理性。     

一种面向云计算服务供应链的安全评估模型

针对云计算服务供应链中存在的安全问题,提出了一种安全评估模型。首先,将供应链风险识别方法与云计算服务场景相结合,识别出了云计算服务供应链的主要风险目标及其风险来源事件集,并以国标《云计算服务安全能力要求》为基础,构建了安全指标体系;其次,考虑到云计算服务供应链的动态开放、复杂多变以及大多安全指标无法量化的特点,设计了基于德尔菲方法的风险来源度量流程和权重赋值流程,并提出了基于模糊综合评价的安全评估流程,以实现风险来源的风险等级度量结果的一致性;最后,通过一个应用实例验证了安全评估模型的有效性和可行性。     

A grid computing based approach for the power system dynamic security assessment

This paper addresses the problem of parallel dynamic security assessment applications from static homogeneous cluster environment to dynamic heterogeneous grid environment. Functional parallelism and data parallelism are supported by each of the message passing interface model and TCP/IP model. To consider the differences in heterogeneous computing resources and complexity of large-scale power system communities, a kernel-based multilevel algorithm is proposed for network partitioning. Since the bottleneck in distributed computation is low speed network communication, a bi-level latency exploitation technique is introduced for numerically solving system differential equations. The proposed grid-based implementation includes the core simulation engine, grid computing middleware, a Python interface and Python front-end utilities. Tests for a 39-bus network, a 4000-bus network and a 10,000-bus network are reported, and the results of these experiments demonstrate that the proposed scheme is able to execute the distributed simulations on computational grid infrastructure and provide efficient parallelism.     

Probabilistic assessment of financial risk in e-business associations

Business activities are a result of carefully formed associations between different users in order to achieve certain pre-decided outcomes. Decision-making in such associations is an important step and transactional risk analysis is one of the integral processes that facilitates this step. This paper presents an approach that determines the negative consequences (termed as financial risk) of forming e-business associations. Unlike other approaches, our model captures the different types of events and their uncertainties to determine the financial risk by using the convolution operator and expressing it as a probabilistic measure rather than as a crisp financial value. Such representation makes sense as the financial risk may be determined at a point of time in future where nothing is certain. Depending upon the complexity of the problem, we explain the different ways of using the convolution operator to determine the financial risk. The simulation result shows a better representation and understanding of the financial risk that will provide important inputs to the transactional risk analysis and the decision-making process.     

云计算技术安全风险评估研究

云计算基于开放的互联网,使得其面临众多安全风险问题,为使风险控制在可接受范围,评估是十分必要的。云计算风险因素复杂多样,用德尔菲法建立云计算技术安全风险评估指标体系,凝练了云计算环境下技术风险的主要因素,并用模糊集与熵权理论对其进行评估。通过实例分析,验证了该方法是可行的、有效的。     

Multi-level scheduling for global optimization in grid computing

The paper presents a multi-level scheduling algorithm for global optimization in grid computing. This algorithm provides a global optimization through a cross-layer optimization realized by decomposing the optimization problem in different sub-problems each of them corresponding to one among the grid layers such as application layer, collective layer and fabric layer. The QoS of an abstraction level is a utility function that assigns at every level a different value and that depends on the kind of task that is executed on the grid. The global QoS is given by processing of the utility function values of the three different levels, using the Lagrangian method. Multi-level QoS scheduling algorithm is evaluated in terms of system efficiency and their economic efficiency, respectively. Economic efficiency includes user utility, service provider’s revenue and grid global utility. System efficiency includes execution success ratio and resource allocation ratio.     

Ergonomics risk assessment with digital human models in car assembly: Simulation versus real life

This study investigated how well ergonomics risk assessments on simulations with digital human models (DHM) match real‐life assessments obtained on a car assembly line. Two ergonomists evaluated 20 work tasks in real life and as a DHM simulation using a company‐specific version of the Automotive Assembly Worksheet (AAWS) for assessing static postures, action forces, manual material handling, and extra strains. Results demonstrate that DHM simulations provide good estimations of the workload in real‐life tasks. Additionally, significant correlations were found between AAWS risk assessments and subjectively perceived exertion measured on the Borg scale. Yet, there were also some significant differences in AAWS risk classification and AAWS total scores. DHM simulations appear helpful for reliably detecting static postures and extra strains, whereas action forces are harder to estimate than in real life. It is suggested that comprehensive methods such as AAWS should be incorporated in DHM software for enhancing efficiency and validity of digital ergonomics risk assessment. © 2010 Wiley Periodicals, Inc.     

Fuzzy possibilistic modeling and sensitivity analysis for optimal fuel gas scheduling in refinery

In refinery, fuel gas which is continuously generated during the production process is one of the most important energy sources. Optimal scheduling of fuel gas system helps the refinery to achieve energy cost reduction and cleaner production. However, imprecise natures in the system, such as prediction of production rate of fuel gas, prediction of energy demand of the equipments and cost coefficient in the objective function, make the deterministic optimization method which requires well-defined and precise data cannot be competent for the fuel gas scheduling problem. In this study, fuzzy possibilistic programming (FPP) method is proposed to deal with these imprecise natures by triangular possibility distributions. The fuzzy possibilistic model is transformed into usual mathematical model by definition of necessity measure and the α-level method. Although FPP models have been widely applied to modeling, few research works have been reported on the performance evaluation, namely sensitivity analysis, of these models. Marginal value analysis, which is always used to provide additional economic information, is proposed to give the sensitivity analysis in the paper. This method is demonstrated to be much more flexible than the simulation method. Particularly, the analytical method is adopted to examine how the imprecise natures in the fuel gas system affect the scheduling results.     

网格环境下基于QoS需求的关联任务调度算法*

首先描述QoS调度问题,建立QoS需求模型;然后通过分析任务的依赖性,提出时间花费、资源价格和可靠性三种QoS参数的映射机制;最后针对网格环境的新特征,提出一种以优化用户效用为目标,基于QoS的关联任务调度算法(QBDTS_UO).仿真实验结果表明,该算法能以较小的时间花费为代价,有效满足用户的QoS需求,并能大大提高网格资源的使用率.     

Optimization decomposition approach for layered QoS scheduling in grid computing

The paper presents optimization decomposition based layered Quality of Service (QoS) scheduling for computational grid. Cross layer joint QoS scheduling is studied by considering the global problem as decomposed into three sub-problems: resource allocation at the fabric layer, service composing at the collective layer, and user satisfaction degree at the application layer. The paper proposes a complete solution from optimization modeling, Lagrange relaxation based decomposition, to solutions for each sub-problem Lagrange relaxation based decomposition. These aspects match the vertical organization of the considered grid system: each layer trade with adjacent layers to find a global optimum of the whole grid system. Through multi-layer QoS joint optimization approach, grid global QoS optimization can be achieved. The cross layer 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 owner of each layer obtains inputs from other layers, tries to maximize its own utility and provides outputs back to other layers. This iterative process lasts until presumably all layers arrive at the same solution.     

A bipartite model for load balancing in grid computing environments

In this paper, a bipartite model for load balancing (LB) in grid computing environments, called Transverse viewpoint-based Bi-Tier model (TBT), is proposed. TBT can efficiently eliminate topology mismatching between overlay- and physical-networks during the load transfer process. As an implementation of TBT, a novel LB policy called M²ON (Min-cost and Max-flow Channel based Overlay Network) is presented. In M²ON, the communication capability is denoted as M²C (Min-cost and Max-flow Channel) which is obtained using a Labeled Tree Probing (LTP) method. The computing capacity is denoted as the Idle Factor (IF) which is obtained from the semantic overlay. The higher- and lower-level characteristics are combined into an Integrated Impacting Factor (IIF) using a Double Linear Inserting (DLI) function. Based on IIF, optimal topology matching can be achieved in the LB process. Extensive experiments and simulations have been performed and will be discussed. The results show that M²ON achieves more accurate topology matching with a minimum increment in the overall locating time yet achieving higher system performance as a whole.     

计算网格中动态负载平衡的分布调度模式

网格计算下对资源进行有效的管理和调度可以提高系统的利用率.在对现有若干调度方法的研究和分析基础上,针对计算网格中的负载平衡问题,提出了一种分布式网格作业调度模型,并给出相关算法.算法通过建立主从模式的负载信息收集机制,提供给节点全局负载信息,加速重负载节点的负载转移速度.通过有效的负载平衡模式,解决资源调度中负载平衡及其可靠性问题.