一种基于QoS的业务管理SLS信息模型

为在迅速发展的IP网络上提供各种基于IP的差异性业务,业务提供商必须为客户提供业务等级协议(SLA)以对客户做出服务质量(QoS)的保证。业务等级规范(SLS)是SLA的技术部分,它从技术层面上描述了双方对业务及其QoS要求所达成的协定。为使SLA双方的协商以及QoS的验证能有效进行,必须建立一个能满足不同业务特性的SLS信息模型。文章首先对SLA、SLS以及相关概念进行了阐述,然后提出了一种有效的通用的SLS信息模型并对该模型的组织机制进行了研究。     

云计算服务等级协议初探

云服务已经渗透到各行各业,如何保证其良性发展,如何让用户获得应有的服务质量成为摆在眼前的重要问题。服务等级协议作为一种服务提供商与用户之间协商并签订的一个具有法律约束力的合同,规定了在服务提供过程中双方所承担的商务条款,该协议的研究对云服务的健康持续发展有着重要意义。     

PROQOS—Dynamic SLA Management in DiffServ Space Links

Several base elements for the provision of quality of service guarantees have been developed in the recent past. Of these, the Differentiated Services (DiffServ) architecture stands out as the most promising. In spite of this, various issues remain, especially when multidomain DiffServ services are concerned. In this case, some forms of distributed management of Service Level Agreements that allow the specification, exchange, enforcement and monitoring of quality of service data must be in place. Although, again, some isolated solutions exist for each of these problems, considerable effort is necessary to make them work together. The project presented in this paper tried to assess the feasibility of providing differentiated quality of service in satellite IP networks, by developing a dynamic Service Level Agreement management solution for an IP over Digital Video Broadcast Satellite system. The functionality of the implemented system comprises system configuration, dynamic SLA negotiation, QoS monitoring and metering, SLA conformance checking, and QoS reporting to customers.     

Efficient Agent-Based Selection of DiffServ SLAs over MPLS Networks Within the ASP Service Model

The demand for QoS provisioning support over Internet grows continuously. One of the factors contributing to this demand is the increasing penetration of Application Service Providers (ASPs) to the market. This necessitates the development of mechanisms for the efficient realization of Service Level Agreements (SLA). In this paper, we develop and evaluate an approach for efficient SLA selection and implementation (support, policing/shaping, and charging) in a DiffServ-over-MPLS network domain. We describe how this approach is applied in a realistic service provision scenario based on the ASP service model. A negotiation process between a user and a network provider is introduced; thus the user can choose from the alternative options for allocation of resources the one that better matches his needs. For the purposes of negotiation, we develop an appropriate utility model that expresses user preferences in a simple yet informative way. Furthermore, we discuss the implementation of our approach in a small-scale experimental DiffServ-over-MPLS network, for the case of a simple scenario of ASP services provision. We also assess the economic efficiency of our approach by means of simulation experiments, the results of which advocate that our approach is incentive compatible, in the sense that individual optimization by each user (in SLA selection) also leads to improved social welfare. Our approach is quite general and can be combined with several policies for network management, or as a complement to the traffic engineering procedures.     

Monitoring web services’ quality of service: a literature review

Monitoring Quality of Service (QoS) compliance is an important procedure in web service environment. It determines whether users’ expectations are met, and becomes the vital factor for them to decide whether to continue paying for the service or not. The monitoring is performed by checking the actual services performance against the QoS stated in Service Level Agreement (SLA). In relation to that, the need for monitoring vague QoS specifications in SLA has become more apparent nowadays. This paper reviews the published literature on web services QoS monitoring. A total of 60 selected articles were systematically analyzed. There were 23 of the articles selected through restrictive search criteria while the other 37 were selected based on unrestrictive search criteria. The review shows that little evidence exists on monitoring vague QoS specifications of web services. Providing ability for monitoring QoS that is specified vaguely in SLA could give new insights and implications to web services field. This paper concludes with some recommended future works to construct the theory and perform the empirical research.     

Specification of Service Level Agreements: Problems, Principles and Practices

Software intensive systems (SIS) increasingly influence the ability of enterprises to be competitive in continuously changing market situations. The integration of these systems into organizations, and in particular the subsequent exploitation, maintenance and service activities, have become of utmost importance. Unfortunately the area of exploitation and operation, also known as service management, is still rather immature. Service management covers services such as performance and availability support, end-user and help desk support, education, and maintenance. One of the main concepts of service management is the Service Level Agreement (SLA). The goal of an SLA is to bridge the gap between service provider and users or customers. However, there exist many problems and unsolved questions regarding the specification and the quantification of SLAs. This paper addresses the specification of SLAs on the basis of three well-founded service management principles, respectively: 'continuity in service management, the pit/shell principle of a service, and the principle of specifying the quality of both a service process and a service object. Finally, the paper addresses the validation of these principles in practice.     

A Service Level Agreement Language for Dynamic Electronic Services

This paper proposes a novel language for Service Level Agreements (SLAs) for dynamic and spontaneous electronic services. In a cross-organizational setting, it is important for customers of a service to obtain, monitor and enforce quality of service (QoS) guarantees by service providers, usually expressed in the form of SLAs. Since the supervision and management of SLAs and the provisioning of corresponding systems should be automated for economic reasons, we need a formal language to define an SLA. If, moreover, providers and customers want to sign custom-made SLAs, the SLA language, correspondingly, must provide a large degree of flexibility.The SLA language described in this paper aims at providing the needed flexibility by means of an XML-based representation and a runtime system for SLAs. Using this language, parties to an SLA can describe how parameters are measured and computed from raw metrics, the guarantees they want with respect to those parameters and the involvement of third parties to, e.g., independently verify SLA compliance.     

A fuzzy Grid-QoS framework for obtaining higher grid resources availability

A computational grid ensures the on-demand delivery of computing resources, in a security-aware, shared, scalable, and standards-based computing environment. A major concern is how to evolve a general and an encompassing framework that guarantees users’ satisfaction measured as Quality of Services (QoS). To obtain a higher QoS, effective QoS perceived by subscribers (users) must conform to specified QoS agreements in the Service Level Agreements (SLAs) document—a legal contract between the Grid Services Provider (GSP) and users. Sometimes the effective user QoS does not conform to the specifications in the SLA because of the vagueness in linguistic definitions in the SLA. Existing approaches overcommitted resources to meet QoS. In this paper, we propose a fuzzy logic framework for calibrating a grid resources user-QoS that addresses the vagueness in linguistic definitions of the SLA document without overcommitting grid resources.     

OntoSLAt:本体支持的SLA建模及管理

服务等级协定SLA（Service Level Agreements）目前多样化网络服务中服务质量保障的重要手段，但SLA存在诸如缺乏统一信息模型、重用度低等问题，而语义网中的本体论为解决目前SLA中存在的问题提供了有效的技术支持．本文采用本体来对SLA模板进行建模，为SLA概念、参数和度量提供严格的、统一的和富含语义的定义．在此基础上，对如何利用本体来组织和构建SLA模板知识库（OntoSLAt）进行阐述．基于SLA本体的匹配算法可依据服务需求描述对相应网络服务进行有效的匹配，并给出基于QoS的选择；而SLA模板生成算法用于从SLA知识库中重构生成新的模板，以便有效地实现SLA重用．     

基于SLA与用户评价的云计算信任模型

针对用户对云服务提供商缺乏信任的问题,提出一个基于服务等级协议(SLA)与用户评价的云计算信任模型。通过分析云服务提供商的SLA确认其承诺的服务质量,根据用户的评价确定云服务提供商对SLA的履行情况,综合两方面内容计算云服务的可信度。分析结果表明,借助该模型,用户可以准确地选择可信的云服务提供商。     

Service level agreements for DiffServ-based services' provisioning

The evolution of mechanisms for providing Quality-of-Service (QoS) over the contemporary network infrastructures has introduced the need for regulation and management of the emerging QoS services with the use of Service Level Agreements (SLAs). SLAs define the qualitative and quantitative characteristics of the services provided from a network provider to peering networks or customers. In this work, we define a template for the SLA structure to support the provision of a QoS service between two peering domains and then we proceed with the definition of an end-to-end SLA across consecutive domains, based on the bilateral ones. We also propose a model for the service provisioning procedures.     

基于延时测量的端到端路径性能检测

网络路径的端到端性能直接决定了为用户提供服务的质量,网络路径性能的测量是网络运营和SLA(ServiceLevelAgreement)验证的重要组成部分。文章在描述端到端路径性能检测的一般性问题的基础上,提出了延时差平稳系数和绝对平稳系数作为测量检测网络路径性能的几个评价指标,作为已有的测量标准化工作的补充和利用网络测量进行端到端性能管理的参考方法。     

基于服务等级的网格服务质量描述语言

针对网格服务质量管理中使用服务水平协议(SLA)带来较大协商开销的问题,提出基于服务等级的网格服务质量描述语言即网格服务等级语言(CGSL)及建立在CGSL之上的网格服务质量管理框架.服务等级是轻量级SLA,提供一种区分不同服务质量的机制.CGSL基于XML技术和WSRF规范,与Web服务描述语言(WSDL)兼容,用于描述网格服务提供方所能提供的不同服务等级,为监控服务质量提供具体信息.网格服务质量管理框架建立在CGSL之上,并通过Mobile Agent监控服务质量是否得到满足.一个具体的文件存储网格服务实例用来展示CGSL在网格服务质量管理中的应用.该实例表明CGSL以少量的服务等级代替复杂的SLA,能有效降低运行时消耗,适合异构多变的网格环境.     

The WSLA Framework: Specifying and Monitoring Service Level Agreements for Web Services

We describe a novel framework for specifying and monitoring Service Level Agreements (SLA) for Web Services. SLA monitoring and enforcement become increasingly important in a Web Service environment where enterprise applications and services rely on services that may be subscribed dynamically and on-demand. For economic and practical reasons, we want an automated provisioning process for both the service itself as well as the SLA managment system that measures and monitors the QoS parameters, checks the agreed-upon service levels, and reports violations to the authorized parties involved in the SLA management process. Our approach to these issues is presented in this paper. The Web Service Level Agreement (WSLA) framework is targeted at defining and monitoring SLAs for Web Services. Although WSLA has been designed for a Web Services environment, it is applicable as well to any inter-domain management scenario, such as business process and service management, or the management of networks, systems and applications in general. The WSLA framework consists of a flexible and extensible language based on XML Schema and a runtime architecture comprising several SLA monitoring services, which may be outsourced to third parties to ensure a maximum of objectivity. WSLA enables service customers and providers to unambiguously define a wide variety of SLAs, specify the SLA parameters and the way they are measured, and relate them to managed resource instrumentations. Upon receipt of an SLA specification, the WSLA monitoring services are automatically configured to enforce the SLA. An implementation of the WSLA framework, termed SLA Compliance Monitor, is publicly available as part of the IBM Web Services Toolkit.     

Automatically generating consistent schedules for multimedia documents

A schedule for a multimedia document indicates when document events should occur. We describe a two-phase algorithm that automatically produces schedules for interactive multimedia documents, which can contain both predictable behavior (such as audio and video) and unpredictable behavior (such as user interaction and programs with unpredictable execution times). The first phase of the algorithm, called the compiletime scheduler, preprocesses high-level temporal specifications before the document is presented and creates as much of the schedule as possible. Our compiletime scheduler is conceptually similar to T_EX's spatial layout algorithm in that it permits time to be stretched or shrunk between events inside media segments to arrive at an optimal presentation for a document. The second phase of the algorithm, called the runtime scheduler, resolves the presentation of media segments that depend upon unpredictable behavior.     

Trading availability among shared-protected dynamic connections in WDM networks

Novel automatized management systems for optical WDM networks promise to allow customers asking for a connection (i.e., a bandwidth service) to specify on-demand the terms of the Service Level Agreement (SLA) to be guaranteed by the Network Operator (NO). In this work, we exploit the knowledge, among the other Service Level Specifications (SLS), of the holding time and of the availability target of the connections to operate shared-path protection in a more effective manner.In the proposed approach, for each connection we monitor the actual downtime experienced by the connection, and, when the network state changes (typically, for a fault occurrence, or a connection departure or arrival), we estimate a new updated availability target for each connection based on our knowledge of all the predictable network-state changes, i.e., the future connection departures. Since some of the connections will be ahead of the stipulated availability target in their SLA (credit), while other connections will be behind their availability target (debit), we propose a mechanism that allows us to “trade” availability “credits” and “debits”, by increasing or decreasing the shareability level of the backup capacity. Our approach permits to flexibly manage the availability provided to living connections during their holding times.The quality of the provided service is evaluated in terms of availability as well as probability of violation of availability target stipulated in the SLA (also called SLA Violation Risk), a recently-proposed metric that has been demonstrated to guarantee higher customer satisfaction than the classical statistical availability. For a typical wavelength-convertible US nationwide network, our approach obtains significative savings on Blocking Probability (BP), while reducing the penalties due to SLA violations. We also analytically demonstrate the proposed scheme can be highly beneficial if the monitored metric is the SLA Violation Risk instead of the availability.     

A cost-aware auto-scaling approach using the workload prediction in service clouds

Service clouds are distributed infrastructures which deploys communication services in clouds. The scalability is an important characteristic of service clouds. With the scalability, the service cloud can offer on-demand computing power and storage capacities to different services. In order to achieve the scalability, we need to know when and how to scale virtual resources assigned to different services. In this paper, a novel service cloud architecture is presented, and a linear regression model is used to predict the workload. Based on this predicted workload, an auto-scaling mechanism is proposed to scale virtual resources at different resource levels in service clouds. The auto-scaling mechanism combines the real-time scaling and the pre-scaling. Finally experimental results are provided to demonstrate that our approach can satisfy the user Service Level Agreement (SLA) while keeping scaling costs low.     

SLA-based complementary approach for network intrusion detection

Enhancing the intrusion detection system is essential to maintain user confidence in network services security. However, the threat of intruders on Internet services is prevalent. This paper proposes a distributed edge-to-edge complementary approach for intrusion detection in a DiffServ/MPLS domain. The QoS metrics are inspected at the edges routers to determine anomalous behavior in the network traffic. Consumed ratios of one-way delay variation (OWDV) and packet loss are computed to monitor service level agreement (SLA) violations. The bandwidth ratio is measured to differentiate abnormal from normal traffic as well as to detect multiple intrusions launched simultaneously. We employed SLA as a comparison scale to infer the deviation between the users consumed ratios and the predefined ratios in the SLA. Service violation occurs and intrusion may be launched when the predefined ratios are exceeded. The complementary services of DiffServ and MPLS techniques guarantee accurate measurements, whereas the complementary measurements of active and passive techniques immunize network performance against scalability limitation. Simulation results indicate that the proposed approach is capable of monitoring SLA violations and can filter out traffic of intruders who breach SLA without disturbing the normal traffic of legitimate users.     

Distributed Admission Control for QoS and SLS Management

This article proposes a distributed admission control (AC) model based on on-line monitoring to manage the quality of Internet services and Service Level Specifications (SLSs) in class-based networks. The AC strategy covers intra- and interdomain operation, without adding significant complexity to the network control plane and involving only edge nodes. While ingress nodes perform implicit or explicit AC resorting to service-oriented rules for SLS and QoS parameters control, egress nodes collect service metrics providing them as inputs for AC. The end-to-end operation is viewed as a cumulative and repetitive process of AC and available service computation. We discuss crucial key points of the model implementation and evaluate its two main components: the monitoring process and the AC criteria. The results show that, using proper AC rules and safety margins, service commitments can be efficiently satisfied, and the simplicity and flexibility of the model can be explored to manage successfully QoS requirements of multiple Internet services.     

私有云平台服务能力检测方法

针对现阶段使用私有云评测方法缺失所导致搭建私有云供需不匹配的问题,提出了一种自适应、可扩展的私有云系统能力检测方法,可对基础设施即服务（IaaS）云计算系统能力进行评测。首先,通过私有云应用程序接口动态扩展虚拟机数量;然后,通过性能特征模型选取虚拟机所需配置的硬件信息和操作系统类别,并根据用户的需求差异使用不同的负载模型,形成相应的模拟运行环境;最后,使用云计算服务等级协议（SLA）作为测试标准来衡量私有云服务能力。使用所提方法对Openstack开源私有云平台的能力进行了评测,实验结果表明,所提方法可以准确得出私有云服务能力,结果和用户实测一致。该方法负载生成成本更低,测试效率更高。并将该方法与Openstack自带的组件Rally进行对比,拓展性和负载动态模拟有很大的改进。