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Towards Automated SLA Management for Web Services
Abstract
In order to automate SLA management it is essential to specify SLAs in precise and unambiguous manner as well as keep the specification flexible. While precision will help automate the process of monitoring and metric collection, flexibility will enable extending it to unforeseen service level agreement specifications. Abstract: In order to automate SLA management it is essential to specify SLAs in precise and unambiguous manner as well as keep the specification flexible. While precision will help automate the process of monitoring and metric collection, flexibility will enable extending it to unforeseen service level agreement specifications.
... The quality of these "new" web services is not only stated in terms of constraints on provided performance. For example, traditional Service Level Agreements (SLA) or Service Level Objectives (SLO) [25] usually constrain the maximum allowed response time. An ML-service must also be accurate. ...
... Fashion-MNIST Linear Quadratic Linear Quadratic r E r AC r E r AC r E r AC r E r AC r 1 1 0. 25 latter receives a gray-scale image of a fashion item and outputs the corresponding class (e.g., t-shirt, bag). ...
In recent years, Web services are becoming more and more intelligent (e.g., in understanding user preferences) thanks to the integration of components that rely on Machine Learning (ML). Before users can interact (inference phase) with an ML-based service (ML-Service), the underlying ML model must learn (training phase) from existing data, a process that requires long-lasting batch computations. The management of these two, diverse phases is complex and meeting time and quality requirements can hardly be done with manual approaches.This paper highlights some of the major issues in managing ML-services in both training and inference modes and presents some initial solutions that are able to meet set requirements with minimum user inputs. A preliminary evaluation demonstrates that our solutions allow these systems to become more efficient and predictable with respect to their response time and accuracy.
KeywordsMachine learningRuntime managementService orchestration
... The quality of these "new" web services is not only stated in terms of constraints on provided performance. For example, traditional Service Level Agreements (SLA) or Service Level Objectives (SLO) [25] usually constrain the maximum allowed response time. An ML-service must also be accurate. ...
... Fashion-MNIST Linear Quadratic Linear Quadratic r E r AC r E r AC r E r AC r E r AC r 1 1 0. 25 latter receives a gray-scale image of a fashion item and outputs the corresponding class (e.g., t-shirt, bag). ...
In recent years, Web services are becoming more and more intelligent (e.g., in understanding user preferences) thanks to the integration of components that rely on Machine Learning (ML). Before users can interact (inference phase) with an ML-based service (ML-Service), the underlying ML model must learn (training phase) from existing data, a process that requires long-lasting batch computations. The management of these two, diverse phases is complex and meeting time and quality requirements can hardly be done with manual approaches. This paper highlights some of the major issues in managing ML-services in both training and inference modes and presents some initial solutions that are able to meet set requirements with minimum user inputs. A preliminary evaluation demonstrates that our solutions allow these systems to become more efficient and predictable with respect to their response time and accuracy.
... To establish such automated SLA management, the SLA must be specified unambiguously. In [14], we represent the SLA specification language we developed for that purpose. This specification language relies on a managed object model for web services presented in [IS]. ...
... This is determined by the SLA specification. The details of the SLA specification are given in [14], but the important attributes are evalFunc, evalWhen and measuredAt. measuredAt specifies which service (and thus which intermediary) collects the data, and evalWhen specifies at what moments in time to collect the data. ...
We introduce the architecture, object model, components, and protocols of a management overlay for federated service management, called Web Services Management Network (WSMN). WSMN targets management of web services that interact across administrative domains, and therefore typically involves multiple stakeholders (examples are business-to-business, service provider interconnections, help desks). The architecture is based on (implicit) SLAs to formalize relations across domains. It relies on a network of communicating service intermediaries, each such intermediary being a proxy positioned between the service and the outside world. WSMN also exchanges control information to agree on what to monitor, where to monitor, and whom to provide visibility.
... Dynamic ESOA/ECSA infrastructure requires dynamic resource management or an elastic cloud based on demand. This requires the system to have some degree of automation and adaptation (Sahai, A., Durante, A., & Machiraju, V., 2001) (Chung, L., & Subramanian, N., 2003) . The dynamic SLM needs to use automated SLA monitoring, diagnostics, and configurable and reconfigurable adaptation for managing SLA-Aware enterprise service systems (Beauche, S. & Poizat, P., 2008) (Gao, T. et al., 2005) (Sahai, A., et al. 2002). ...
When deployed as infrastructure components of real-time business processes, service computing applications we rely on for our daily activities elicit the proper addressing of performance and dependability issues. While recent developments in service-oriented architectures have come a long way in many aspects, ranging from semantics and ontologies to frameworks and design processes, performance and dependability remains a research demanding field.
Performance and Dependability in Service Computing: Concepts, Techniques and Research Directions highlights current technological trends and related research issues in dedicated chapters without restricting their scope. This book focuses on performance and dependability issues associated with service computing and these two complementary aspects, which include concerns of quality of service (QoS), real-time constraints, security, reliability and other important requirements when it comes to integrating services into real-world business processes and critical applications.
... Reliability of a service is a critical factor in the adoption of services (Kreger 2003), is considered an important QoS specification of a service (Ran 2003), and is often included in SLAs (Sahai et al. 2002). Drawing from the standard definition of software reliability, which is characterized as "the ability of a system or component to perform its required functions under stated conditions for a specified period of time" (Board 1991), service reliability can be viewed as the probability that the service will exhibit failure-free operation during a specified period. ...
The need to create and deploy business application systems rapidly has sparked interest in using web services to compose them. When creating mission-critical business applications through web service compositions, in addition to ensuring that functional requirements are met, designers need to consider the end-to-end reliability, security, performance, and overall cost of the application. As the number of available coarse-grain business services grows, the problem of selecting appropriate services quickly becomes combinatorially explosive for realistic-sized business applications. This article develops a business-process-driven approach for composing service-oriented applications. We use a combination of weights to explore the entire QoS criteria landscape through the use of a multi-criteria genetic algorithm (GA) to identify a Pareto-optimal multidimensional frontier that permits managers to trade off conflicting objectives when selecting a set of services. We illustrate the effectiveness of the approach by applying it to a real-world drop-ship business application and compare its performance to another GA-based approach for service composition.
... To this end, we consider CPU-bound services (e.g., calculate visual effects, perform compute-intensive scientific calculations) since the processor is the major contributor to the overall power demand of a server [1,11]. From performance perspective, we consider mean response time as it is an essential metric used in service level agreements (SLAs) [5,13,15]. Taking into account both service performance and processor's power demand, we propose a Markov Chain model for the Conservative governor that takes as input parameters the mean arrival and service rates of a CPU-bound service, the sampling interval of the governor, the utilization thresholds that determine when to scale up/down frequency and voltage, and the idle and loaded power consumption of the processor for all available frequency/voltage combinations. ...
Dynamic voltage and frequency scaling (DVFS) is a mechanism adopted by major hardware vendors to reduce power demand during times of low processor utilization. However, reducing processor frequency to decrease power demand usually results in degraded services' performance leading to service level agreement violations. Governors, which are a piece of software at kernel level, are devised to exploit the flexibility provided by DVFS technologies of the hardware. Utilization-based governors change frequency and voltage at discrete time instances based on workload's utilization without taking into account performance constraints of services. In this paper, a model for the utilization-based Conservative governor is proposed. The model allows us to predict both service performance (mean response time) and processor power demand. An M/M/1 simulator is presented which is used to validate the accuracy of the proposed model. For model accuracy validation, a second methodology based on the frequency probabilities of the processor is proposed. Both approaches confirm the derived DTMC model. We also carry out a comparison between On-demand and Conservative governors and show that the latter performs better for Markovian workloads.
... QoS measurement of Web services has been used in the service level agreement (SLA) [43], such as IBM's WSLA framework [33] and the work from HP [56]. In SLA, the QoS data are mainly for the service providers to maintain a certain level of service to their clients, and the QoS data are not available to others. ...
Quality-of-Service (QoS) is normally used to describe the non-functional characteristics of Web services and as a criterion for evaluating different Web services. QoS Management of Web Services presents a new distributed QoS evaluation framework for these services. Moreover, three QoS prediction methods and two methods for creating fault-tolerant Web services are also proposed in this book. It not only provides the latest research results, but also presents an excellent overview of QoS management of Web sciences, making it a valuable resource for researchers and graduate students in service computing. Zibin Zheng is an associate research fellow at the Shenzhen Research Institute, The Chinese University of Hong Kong, China. Professor Michael R. Lyu also works at the same institute.
... Much research work has been done on service's quality definition and description for Internet and Web services [62,66]. Efforts such as WSML [74], WSLA [76], DAML-QoS [75], OWL-Q [62] are trying to make QoS description more flexible to describe and present the formal description of a service. To address nonstandardized QoS metrics and attributes, a mechanism for mapping SLAs is studied in [70]. ...
Content adaptation bridges the mismatch between rich contents and user preferences along with the end device capability. This thesis addresses five key issues: enabling content adaptation as services; locating and selecting best possible services in the network; and negotiating, providing and managing quality assurance of a service.<br /
... There are some solutions to specify the services quality that had origin in the web services community. In (Sahai, Durante, & Machiraju, 2002) the authors show how to use Web Service Description Language (WSDL) and Web Service Flow Language (WSFL) to specify SLAs. However, this work suffers from the web vision tunnel as it is focused on the web services and does not try to specify business services. ...
Each service interaction between a provider and a customer is an opportunity for the provider to delight, satisfy or disappoint the customer. However, the customers' expectations may change on every interaction. Therefore, defining Service Level Agreements (SLAs) at design time and then restricting the customers' options limits the possibilities for the customers to express their expectations. This is one of the reasons why the services quality is suffering from gaps identified more than two decades ago. In this paper, the authors propose a service quality approach such that SLAs can be specified at execution time (dynamic service levels) in contrast to the usual static SLAs specified at design time. They evaluated the proposal's impact in the service quality gaps using SERVQUAL. The proposal showed improvements in three of the five dimensions measured by SERVQUAL.
... When composing complex workflows out of individual services these quality requirements can be interpreted as mutual agreements. Such agreements can be expressed for example by Web Service Level Agreement Language (WSLA) [16], or Web Service Management Language (WSML) [17]. In our context, a service provider is none other than a worker who has some skills and a task provider's confidence in results would be based upon the worker's credentialed skills. ...
Crowdsourcing continues to gain more momentum as its potential becomes more recognized. Nevertheless, the associated quality aspect remains a valid concern, which introduces uncertainty in the results obtained from the crowd. We identify the different aspects that dynamically affect the overall quality of a crowdsourcing task. Accordingly, we propose a skill ontology-based model that caters for these aspects, as a management technique to be adopted by crowdsourcing platforms. The model maintains a dynamically evolving ontology of skills, with libraries of standardized and personalized assessments for awarding workers skills. Aligning a worker’s set of skills to that required by a task, boosts the ultimate resulting quality. We visualize the model’s components and workflow, and consider how to guard it against malicious or unqualified workers, whose responses introduce this uncertainty and degrade the overall quality.
... The majority of current works define SLAs for XML-based web service. Among these languages, we find the Web Service Level Agreement (WSLA) from Ludwig et al. (2003), the Web Service Management Language (WSML) from Sahai et al. (2002) and SLAs for web services (SLAng) from Lamanna et al. (2003). In addition, the Web Services Agreement Specification (WS-Agreement) of Czajkowski et al. (2003) is a formal specification of agreements using XML, for grid services. ...
Non-functional properties (NFPs) play an important role in the service-oriented architecture (SOA). Consumer-centric NFPs are the NFPs that should be included in a service description to help service consumers decide whether a given service suits their needs. They can hence be used to enable NFP-based service selection and composition. However, nowadays, NFPs are often simply not advertised or are described in ad-hoc proprietary ways. Three important factors impede on the proper handling of NFPs in service descriptions: 1) the neglect of consumer perspectives in SOA; 2) the lack of adequate descriptive mechanisms for a number of NFPs; 3) a good understanding of NFP composability. This paper contributes a concrete syntax for an externally consented catalogue of 17 consumer-centric NFPs, together with composition algorithms that can be effectively used for defining, selecting, and composing services for NFP-aware SOA-based application designs. A realistic use case is used to illustrate the NFP composition algorithms. The NFP catalogue is also validated through its proof-of-concept integration with a mainstream technology: Web Service Description Language (WSDL).
... Similarly, Koller and Schubert (2007) present architecture for autonomous QoS management based on SLA specifications. The paper by Sahai et al. (2001) sketches a general scheme for Service Level Agreements which allows the autonomic management in services systems. In the same direction, the paper by Raimondi et al. (2008) presents the implementation of an automated SLA monitoring for services. ...
In recent years the emergence of Software as a Service (SaaS) provision and cloud computing in general had a tremendous impact on corporate information technology. While the implementation and successful operation of powerful information systems continues to be a cornerstone of success in modern enterprises, the ability to acquire IT infrastructure, software, or platforms on a pay-as-you-go basis has opened a new avenue for optimizing operational costs and processes. In this context we target elastic SaaS systems with on-demand cloud resource provisioning and implement an autonomic management artifact. Our framework forecasts future user behavior based on historic data, analyzes the impact of different workload levels on system performance based on a non-linear performance model, analyzes the economic impact of different provisioning strategies, derives an optimal operation strategy, and automatically assigns requests from users belonging to different Quality of Service (QoS) classes to the appropriate server instances. More generally, our artifact optimizes IT system operation based on a holistic evaluation of key aspects of service operation (e.g., system usage patterns, system performance, Service Level Agreements). The evaluation of our prototype, based on a real production system workload trace, indicates a cost-of-operation reduction by up to 60 percent without compromising QoS requirements.
... Similarly, the paper by (Koller & Schubert 2007) presents architecture for autonomous QoS management based on SLA specifications. The paper (Sahai et al. 2001) sketches a general scheme for Service Level Agreements which allows the autonomic management in services systems. In the same direction, the paper by presents the implementation of an automated SLA monitoring for services. ...
Informationssysteme sind heute ein elementarer Bestandteil moderner Unternehmen. Sie erlauben die Echtzeitüberwachung aller Geschäftsprozesse entlang der Wertschöpfungskette und ermöglichen kostengünstige und schnelle Kommunikation mit Kunden und Zuliefern. Allerdings macht die schnell steigende Komplexität und Nachfrage nach modernen Informationssystemen ihren nachhaltigen und effizienten Betrieb zu einer neuen Herausforderung in der Unternehmensführung.
Eine genauere Analyse der gegenwärtigen IT Situation offenbart einen verschwenderischen Umgang mit Rechenressourcen. Viele kommerzielle Rechenzentren sind durch eine niedrige durchschnittliche Auslastung gekennzeichnet. Die Gründe für diese Ineffizienz sind unter anderem, dass Informationssysteme normalerweise für die maximale zu erwartende Nutzlast skaliert werden. Im Betrieb sind sie jedoch stark schwankender Last ausgesetzt. Darüber hinaus werden sie oft mit einem starken Fokus auf die Service Qualität entwickelt. Kostenfaktoren werden daher oft als zweitrangig betrachtet. Inzwischen ist diese Problematik sehr bekannt und unter dem Namen Green IT sind bereits eine Vielzahl von Konzepten entwickelt worden, um die Umweltbelastung von IT zu reduzieren als auch die Betriebskosten zu senken. Aufgrund der höheren Komplexität großer IT Systeme, sind diese Konzepte allerdings für diese oft nicht vollständig anwendbar.
Eine Möglichkeit für den effizienten und flexiblen Betrieb von großen Informationssystemen sind elastische Systeme. Dieses neue Software Design Paradigma erlaubt den ressourcendynamischen Betrieb und ermöglicht die Ausnutzung der Vorteile von Cloud Computing zur schellen Ressourcen Allokation. Insbesondere erlaubt dieses Konzept das Hinzufügen und Entfernen von Ressourcen während der Laufzeit und somit die Anpassung der Infrastruktur an die aktuelle Nutzlast im Betrieb. Obwohl das Potenzial dieser neuen Methode allgemein anerkannt ist, müssen noch zahlreiche Probleme gelöst werden um einen bereiten Einsatz dieser neuen Technologie zu ermöglichen.
Basierend auf dem aktuellen Stand von IT in Unternehmen werden in dieser Arbeit verschiedene Modelle und Konzepte für den effizienten und nachhaltigen Betrieb von Unternehmensanwendungen entwickelt. Die Komplexität und Heterogenität in diesem Bereich erfordert die Entwicklung und Umsetzung von ganzheitlichen Modellen für das Management und den Betrieb dieser Systeme. Daher, um die maximale Effizienz im Betrieb zu erreichen, müssen alle Einflussfaktoren eines Informationssystems berücksichtigt werden. Dies umfasst unter anderem das Nuterzverhalten, die Systemcharakteristiken, Konfigurationszeiten, Qualitätsanforderungen und wirtschaftliche Aspekte, wie Betriebskosten oder Vertragsvereinbarungen.
Die Einleitung im ersten Kapitel führt in diesem Kontext die fünf Hauptforschungsfragen ein, die in den nachfolgenden Kapiteln jeweils behandelt werden. Die ersten drei Forschungsfragen beschäftigen sich primär mit dem Betrieb von Informationssystemen während die letzten beiden den wirtschaftlichen Aspekten von Unternehmens IT adressieren. Das zweite Kapitel stellt das Tecless Model vor, ein konzeptionelles Model zum effizienten Betrieb von Unternehmensanwendungen in kommerziellen Rechenzentren. Basierend auf einer ganzheitlichen Evaluierung der System- und Lastcharakteristiken, ermöglicht dieses Model den ressourcendynamischen und qualitätssensitiven Betrieb. Das dritte Kapitel stellt die Adaptation Engine vor, welche für den effizienten und zuverlässigen Betrieb von Informationssystemen in Cloud Umgebungen entwickelt wurde. Im Gegensatz zu Tecless, ist die Adaptation Engine modular aufgebaut und kann an verschiedene Software und Infrastrukturszenarien angepasst werden. Ihre Funktion wird mit Hilfe von zahlreichen Experimenten in einer Testumgebung evaluiert. Das vierte Kapitel präsentiert eine Erweiterung der Adaption Engine zur dynamischen Einbindung von Service Level Agreements in den Betrieb. Durch die kontinuierliche Überwachung des Grads der Service Level Agreement Erfüllung und der automatische Anpassung der Service Level Parameter erlaubt diese Model einen hoch effizienten und risikobewussten Betrieb von Informationssystemen. Anschließend präsentieren Kapitel 5 und 6 die wirtschaftlichen Aspekte des Betriebs von Informationssystemen. Im Speziellen stellt Kapitel 5 ein Modell zur Bestimmung der optimalen Infrastrukturgröße vor, während Kapitel 6 ein Modell zur wirtschaftlichen und risikobewussten Erstellung von Service Level Agreements präsentiert. Insbesondere stellt dieses die Verbindung zwischen der Service Qualität und den Betriebskosten her. Das erlaubt gewinnoptimale und risikoadjustierte Betriebsstrategien für Informationssystem abzuleiten
... QoS measurement of Web services has been used in the service level agreement (SLA) [43], such as IBM's WSLA framework [33] and the work from HP [56]. In SLA, the QoS data are mainly for the service providers to maintain a certain level of service to their clients, and the QoS data are not available to others. ...
This chapter aims at advancing the current state of the art in software fault tolerance for Web services by proposing a systematic and extensible framework. We propose a comprehensive fault tolerance strategy selection framework for systematic design, composition, and evaluation of service-oriented systems. Our framework determines optimal fault tolerance strategy dynamically based on the quality-of-service (QoS) performance of Web services as well as the preferences of service users. © Zhejiang University Press, Hangzhou and Springer-Verlag Berlin Heidelberg 2013.
... Alrifai et al.[2]propose an efficient service composition approach by considering both generic QoS properties and domain-specific QoS properties. QoS measurement of Web services has been used in the service level agreement (SLA)[43], such as IBM's WSLA framework[33]and the work from HP[56]. In SLA, the QoS data are mainly for the service providers to maintain a certain level of service to their clients, and the QoS data are not available to others. ...
This chapter reviews related work, including QoS evaluation of Web services, QoS prediction of Web services, and fault-tolerant Web services.
... QoS measurement of Web services has been used in the service level agreement (SLA) [43], such as IBM's WSLA framework [33] and the work from HP [56]. In SLA, the QoS data are mainly for the service providers to maintain a certain level of service to their clients, and the QoS data are not available to others. ...
This chapter concludes this book and discusses the future work.
... QoS measurement of Web services has been used in the service level agreement (SLA) [43], such as IBM's WSLA framework [33] and the work from HP [56]. In SLA, the QoS data are mainly for the service providers to maintain a certain level of service to their clients, and the QoS data are not available to others. ...
In order to achieve efficient Web service evaluation, this chapter proposes a distributed QoS evaluation framework for Web services. The proposed framework employs the concept of user collaboration, which is the key concept of Web 2.0. In our framework, users in different geographic locations share their observed Web service QoS information. The information is stored in a centralized server and will be reused for other users. Several large-scale distributed evaluations are conducted on real-world Web services, and detailed evaluation results are publicly released for future research.
... QoS measurement of Web services has been used in the service level agreement (SLA) [43], such as IBM's WSLA framework [33] and the work from HP [56]. In SLA, the QoS data are mainly for the service providers to maintain a certain level of service to their clients, and the QoS data are not available to others. ...
The neighborhood-based QoS prediction approach has several drawbacks, including (1) the computation complexity is too high and (2) it is not easy to find similar users/items when the user-item matrix is very sparse. To address these drawbacks, this chapter proposes a neighborhood-integrated matrix factorization (NIMF) approach for Web service QoS value prediction. Our approach explores the social wisdom of service users by systematically fusing the neighborhood-based and the model-based collaborative filtering approaches to achieve higher prediction accuracy.
... QoS measurement of Web services has been used in the service level agreement (SLA) [43], such as IBM's WSLA framework [33] and the work from HP [56]. In SLA, the QoS data are mainly for the service providers to maintain a certain level of service to their clients, and the QoS data are not available to others. ...
The highly dynamic Internet environment makes traditional fault tolerance strategies difficult to be used in the service-oriented environment. In this chapter, we propose an adaptive fault tolerance strategy for Web services, which can determine the optimal fault tolerance strategy dynamically at runtime based on the user preference and service QoS.
... Alrifai et al.[2]propose an efficient service composition approach by considering both generic QoS properties and domain-specific QoS properties. QoS measurement of Web services has been used in the service level agreement (SLA)[43], such as IBM's WSLA framework[33]and the work from HP[56]. In SLA, the QoS data are mainly for the service providers to maintain a certain level of service to their clients, and the QoS data are not available to others. ...
To accurately predict the Web service QoS values, this chapter proposes a neighborhood-based collaborative filtering approach for predicting the QoS values for the current user by employing historical Web service QoS data from other similar users. The proposed approach systematically combines the user-based approach and the item-based approach. Our approach requires no Web service invocations and can help service users discover suitable Web services by analyzing QoS information from their similar users.
... L'ouvrage Foundations of Service Level Management [20] décrit les diérents éléments d'un contrat de services : Parties : les entités concernées par le contrat i.e. les signataires (typiquement le fournisseur et le client) et éventuellement des entités tierces pour eectuer des mesures, Term : la durée de validité du contrat, Service level objectives : les objectifs à respecter (en matière de disponibilité, performance, sécurité), Service level indicators : les métriques (temps de réponse par exemple) que l'on utilise pour vérier que les objectifs sont atteints, Penalties : les sanctions appliquées en cas de non respect du contrat, Scope, limitations : le cadre exact du contrat (portée, limitation, exclusion).Le contrat de services permet de confronter les besoins du client avec les limites du fournisseur. Il doit être à la fois exible pour s'adapter au plus grand nombre de cas et susamment contraint pour qu'il n'y ait pas de malentendus sur la qualité du service fourni.2.5.2 Langages de contrat de services pour les Web ServicesDeux langages WSLA[3] et Web Service SLA[5] ont été proposés an de formaliser ces contrats dans le cas des Web Services.Ils utilisent des syntaxes diérentes. Néanmoins, nous retrouvons, dans chacun des cas, les sections caractéristiques d'un contrat de services, comme le conrme le tableau comparatif.Fig. ...
Stage de DEA. Rapport de stage.
... SLAs were initially contracts that defined things such as allocated bandwidth, quality of networking circuits, etc. SLA research in the networking area is still very active (e.g. [16,17,18]), nevertheless, with the advent of service computing and the "everything as a service" principles, the concept was applied to plenty of different areas and automated SLAs [19] are considered in more recent research. Automation here is related to the absence of human intervention to decide what is acceptable and what not, and perform the negotiation and runtime management. ...
The present dissertation concerns the area of Service Computing. More specifically, it contributes to the topic of enabling IT service stacks with dependability, such that they can be used even further in pragmatic business environments and applications. The instrument used for this purpose is a Service Level Agreement (SLA). The main focus is on SLA Hierarchies, which reflect corresponding Service Hierarchies. SLAs may be established manually, or automatically among software agents; it is mainly the latter case that is considered here.
The thesis contributes by means of a formal problem definition for the construction of SLA hierarchies using a translation process, a management architecture, a formal model for defining penalties and a representation that facilitates the processing of SLAs. Using these tools, it is shown that automated SLA management in hierarchical setups is possible, through an application to Multi-Domain Infrastructure-as-a-Service. Within this specific technical area, different SLA-based resource capacity planning approaches are examined via simulation -- both for online and offline planning. The former case concerns normal runtime operations, and the thesis examines two greedy algorithms with regard to their energy-savings efficiency and their performance. In the latter case, a resource-scarce environment is simulated with the purpose of minimizing penalties from already established SLAs. This is achieved via formally-defined combinatorial models, which are solved and compared to two greedy algorithms.
... Service level objectives are the levels of service that both the users and the service providers agree on, and usually include a set of service level indicators, like availability, performance and reliability. Each aspect of the service level, such as availability will have a target level to achieve [33]. ...
In this paper, an efficient web service selection technique using Service Level
Agreement has been implemented. A modified web service architecture has
been developed by incorporating the SLA based QoS for efficient and
authentic web service selection. The proposed model produces more
appropriate web service selection when compared to existing QoS based
techniques. The model is validated through UDDI creation with user’s
preferences SLA based QoS properties such as response time, availability,
reliability, through put and latency time as service agreements. The
experimental result shows improved web service selection for user’s
preferences web service agreements when compared to QoS based service
selection.
... As a result, these specifications are neither easy to be reused in other contexts and infrastructures, nor easy to be extended for specific domains. Among these languages, we find the Web Service Level Agreement (WSLA) [26] defined by IBM and the Web Service Management Language (WSML) [27] defined by HP. They define their built-in NFP metrics, which make these NFP lists hard to extend in some cases while causing substantial overhead in some scenarios. ...
Information about non-functional properties (NFPs) is rarely explicitly described in Service Oriented Architecture (SOA) services. In particular, there is still no standardized solution addressing what service providers should expose or advertise as NFPs in service descriptions to empower service consumers to decide whether a given ser-vice suits best their needs or not. Our goal is to define a catalogue of generic (i.e., domain independent) non-functional properties to be considered when service descrip-tions are developed. This catalogue should be used to better characterize services and enable consumers to perform advanced applications such as NFP-aware service selection. We have identified an initial catalogue of SOA-related NFPs that are relevant from the perspective of consumers (as opposed to providers). Then, we have designed an online survey and invited international SOA experts in many ap-plication areas to criticize the relevance and definitions of the proposed NFPs and to enhance this catalogue. After analyzing the survey results to synthesize an improved cata-logue, we have validated the new definitions a second time with a subset of the initial participants. We obtained a vali-dated list of 17 NFP definitions for atomic SOA service descriptions relevant from a service consumer's perspective.
... Há várias propostas contemplando de descrição de serviços Web, tais como: WSLA [3], WSOL [4], WSIL [5], OWL-S [6], WSML [7], e Mani e Nagarajan [8]. Com base nesses trabalhos, observam-se importantes questões relativas à semântica das descrições abordadas, tentando diminuir a ambigüidade das definições. ...
... Typical contracts include information about the parties concerned (client, provider, possible third-party entities), the duration of validity of the contract, the objectives of performance (availability, response time,etc), penalties in the case of non-fulfillment of the contract and cases of exceptions where the contract is no longer valid. XML-based languages such as WSLA [10] and Web Service SLA [11] have been proposed to define these parameters in a SLA. A group in the Carleton University in Canada has developed a language WSOL (Web Service Offerings Language) which allows defining various classes of service for the same functional service, but which differ in the QoS level and the price of the service. ...
... Advancements made in that work will be used to guide this project. Other work by IBM [12] and HP Labs [13] towards SLAs for Web Services is also significant. ...
As new generation user services emerge, they will require guaranteed levels of service to be provisioned on demand from the underlying telecommunications network. Provision of these levels of service may require guarantees from many different entities along the telecommunications delivery chain. This paper discusses a project developed to explore the formulation and requirements of these agreements, and the applicability of automated negotiation by intelligent agents in addressing the solution requirements.
The Service Level Agreements (SLA) are e- Contracts that need to be established among business partners and monitored to ensure that web services comply with the agreed Quality of Service values. Establishment of SLA among the component services of a composite service and the users becomes important. The establishment is time consuming when done manually because it involves negotiation of parameters to be agreed by the participants. Hence an algorithm is proposed for automated negotiation and a framework for automated contract establishment is designed and implemented. For web services to be successful, privacy must be protected. Today, privacy has become more important concern for both users and web service provider. More people will use web services if they feel all the information released are secure enough. Privacy can often be guaranteed through security measures. To enable privacy protection for Web services, customers are allowed to specify their preferences about the disclosure of their information. In this paper its demonstrated with a suitable e-Business application of Purchase and Registration of Vehicles along with the privacy is ensured during composition of the individual web services for the customer's details.
The idea of cloud computing aligns with new dimension emerging in service-oriented infrastructure where service provider does not own physical infrastructure but instead outsources to dedicated infrastructure providers. Cloud computing has now become a new computing paradigm as it can provide scalable IT infrastructure, QoS-assured services, and customizable computing environment. However, it still remains a challenging task to provide QoS assured services to serve customers with minimized cost, while also to guarantee the maximization of the business objectives (e.g. margin profit) to service provider and infrastructure provider within certain constraints. In order to address these issues, this chapter proposes a QoS-oriented service computing methodology, and discusses associated topics including service level agreement and associated reference architecture, green service, service metering and metrics, service monitoring, and on-demand resource provisioning. In the case study, we demonstrate how we employ QoS-oriented service computing in a multi-server, multi-user on-line game to facilitate the on-demand resource provisioning to maintain quality of service and quality of experience.
Service-oriented systems are usually composed by heterogeneous Web services, which are distributed across the Internet and provided by organizations. Building highly reliable service-oriented systems is a challenge due to the highly dynamic nature of Web services. In this paper, the authors apply software fault tolerance techniques for Web services, where the component failures are handled by fault tolerance strategies. In this paper, a distributed fault tolerance strategy evaluation and selection framework is proposed based on versatile fault tolerance techniques. The authors provide a systematic comparison of various fault tolerance strategies by theoretical formulas, as well as real-world experiments. This paper also presents the optimal fault tolerance strategy selection algorithm, which employs both the QoS performance of Web services and the requirements of service users for selecting optimal fault tolerance strategy. A prototype is implemented and real-world experiments are conducted to illustrate the advantages of the evaluation framework. In these experiments, users from six different locations perform evaluation of Web services distributed in six countries, where over 1,000,000 test cases are executed in a collaborative manner to demonstrate the effectiveness of this approach.
There is a growing trend towards enterprise system integration across organizational and enterprise boundaries on the global Internet platform. The Enterprise Service Computing (ESC) has been adopted by more and more corporations to meet the growing demand from businesses and the global economy. However the ESC as a new distributed computing paradigm poses many challenges and issues of quality of services. For example, how is ESC compliant with the quality of service (QoS)? How do service providers guarantee services which meet service consumers’ needs as well as wants? How do both service consumers and service providers agree with QoS at runtime? In this chapter, SLA-Aware enterprise service computing is first introduced as a solution to the challenges and issues of ESC. Then, SLA-Aware ESC is defined as new architectural styles which include SLA-Aware Enterprise Service-Oriented Architecture (ESOA-SLA) and SLA-Aware Enterprise Cloud Service Architecture (ECSA-SLA). In addition, the enterprise architectural styles are specified through our extended ESOA and ECSA models. The ECSA-SLA styles include SLA-Aware cloud services, SLA-Aware cloud service consumers, SLA-Aware cloud SOA infrastructure, SLA-Aware cloud SOA management, SLA-Aware cloud SOA process and SLA-Aware SOA quality attributes. The main advantages of viewing and defining SLA-Aware ESC as an architectural style are (1) abstracting the common structure, constraints and behaviors of a family of ESC systems, such as ECSA-SLA style systems and (2) defining general design principles for the family of enterprise architectures. The design principles of ECSA-SLA systems are proposed based on the model of ECSA-SLA. Finally, we discuss the challenges of SLA-Aware ESC and suggest that the autonomic service computing, automated service computing, adaptive service computing, real-time SOA, and event-driven architecture can help to address the challenges.
In a services marketplace where a particular service is provided by multiple service providers, service offerings have to be differentiated against competitor services in order to gain market share. Differentiation of services is also needed for different markets and for different consumer segments. Strategies to differentiate service offerings have to be unintrusive—without requiring major changes to the existing service realization mechanisms. In this article, the authors present Service Flavors, a strategy for service providers to differentiate services. By using this strategy, it is possible to analyze and adapt various aspects of a service that help differentiate it from that of the competitors. The authors model differentiating aspects as policies and also provide a mechanism for enforcing these policies in the middleware.
Dynamic Voltage and Frequency Scaling (DVFS) has become a key technique to reduce power consumption at times of low processor (CPU) utilisation. Reducing CPU frequency usually results in degraded services' performance leading to Service Level Agreement (SLA) violations. Usually, CPU governors change frequency and voltage at discrete time instances based on utilisation without taking into account performance constraints of services. In this paper, a model for the widely used utilisation-based ondemand governor is presented. In contrast to state-of-the-art DVFS approaches, our model explicitly considers the change of frequency and voltage at discrete time instances based on utilisation. The model allows us to estimate both service performance and processor's power demand. Furthermore, the model can be used to determine an optimal voltage and frequency switching strategy in order to achieve a further reduction of energy consumption while ensuring compliance with SLAs. The results obtained from experimental analysis confirm our proposed model.
Service Level Agreements (SLAs) are formal electronic contracts between customers and providers of services, describing the rules governing service consumption. They can be established automatically by software agents given proper target utilities, or may be long-standing indicating less volatile business relationships. This position paper reflects history and state of the art in management of automated Service Level Agreements, and discusses main challenges in this area, in the context of complex service hierarchies and the corresponding SLA hierarchies. Then, it goes on to propose future directions for key topics such as modeling SLAs, planning them during the negotiation phase, monitoring them and enforcing them through adjustment actions.
The idea of cloud computing aligns with new dimension emerging in service-oriented infrastructure where service provider does not own physical infrastructure but instead outsources to dedicated infrastructure providers. Cloud computing has now become a new computing paradigm as it can provide scalable IT infrastructure, QoS-assured services, and customizable computing environment. However, it still remains a challenging task to provide QoS assured services to serve customers with minimized cost, while also to guarantee the maximization of the business objectives (e.g. margin profit) to service provider and infrastructure provider within certain constraints. In order to address these issues, this chapter proposes a QoS-oriented service computing methodology, and discusses associated topics including service level agreement and associated reference architecture, green service, service metering and metrics, service monitoring, and on-demand resource provisioning. In the case study, we demonstrate how we employ QoS-oriented service computing in a multi-server, multi-user on-line game to facilitate the on-demand resource provisioning to maintain quality of service and quality of experience.
Cloud computing, the model for providing on-demand access to a pool of shared
resources with minimum provider interference, is emerging as a substitute to common IT
infrastructure. As increasing numbers of cloud consumers dispatch their workloads to
cloud providers, Service Level Agreement (SLA) between consumers and providers
becomes of paramount importance to guarantee that service quality is preserved at
satisfactory levels regardless of the dynamic nature of the cloud environment. SLA
contains an explanation of the agreed service, parameters of the level of service, the
guarantees regarding the Quality of Service, arrangements and cures for all cases of
violations. In this paper, we provide a study about the general structure of SLA, its
components, the management processes (in particular SLA monitoring), SLA lifecycle,
and pricing. Then, we explore the importance of SLA for cloud computing services related
to both the cloud user and the service provider including the differences between SLA for
cloud services and other Web services. Finally, we present a comparison between the
current major cloud computing service providers in terms of SLA’s
Nowadays, likewise the functionality of a web service, Quality of Service (QoS) has become an essential feature of web service characteristic for users to select the suitable web services for a distributed application by identifying which characteristics make service more qualified to be selected. Although proposed QoS models by existing works may satisfy the required quantitative measurement of QoS attributes, clustering all generic quality attributes in a same group may have a negative impact on technical QoS attributes such as Response time. Consequently, from technical point of view, lack of a comprehensive model to evaluate web services in terms of technical and non-technical QoS attributes is an important issue on topic, affecting the accuracy of the results in general, and is addressed in this paper.
It is paramount to provide seamless and ubiquitous access to rich contents available online to interested users via a wide range of devices with varied characteristics. Recently, a service-oriented content adaptation scheme has emerged to address this content-device mismatch problem. In this scheme, content adaptation functions are provided as services by third-party providers. Clients pay for the consumed services and thus demand service quality. As such, negotiating for the QoS offers, assuring negotiated QoS levels and accuracy of adapted content version are essential. Any non-compliance should be handled and reported in real time. These issues elevate the management of service level agreement (SLA) as an important problem. This chapter presents prior work, important challenges, and a framework for managing SLA for service-oriented content adaptation platform.
The cloud services have offered new possibilities for services fulfilment and although the cloud has been a technology breakthrough, the problems it raises go beyond technical issues. Indeed, the organization-oriented issues related to cloud services are getting more attention and the dialogue is moving away from technical to non-technical issues. Our research deals with the gap between customers’ expectations and the perceived service, a problem that we also found in the cloud services area. We propose to close this gap by formally specifying the customers’ expectations into Service Level Agreements (SLAs) using a process based on the Enterprise Ontology. We have already evaluated this proposal in several contexts (from public city councils to private banks) and in this paper we describe a field study in a cloud services provider. The evaluation was positively carried out by means of interviews, the Four Principles from Österle et al., and the Moody and Shanks Quality Framework.
Lately, the evolution of information technologies has been following two trends. On the one hand the proliferation of communicating devices contributes to the creation of an ambient intelligence. On the other hand, the booming of Internet associated with the rapid growth of data centres capabilities results in the emergence of an internet of services. In both domains, application design is challenged by the dynamic availability of computing resources and data. The combination of component-based software engineering and service-oriented computing techniques allows service bindings to be driven by policies. However, for the time being, policies either follow a dynamic approach which does not suit the needs of architectural stability when dealing with intermittent services, or a static approach which does not allow dynamic reconfiguration. The work presented in this thesis proposes a trade-off between the two approaches by considering service disruptions as a major concern. The proposed binding policy relies on service level agreements to be disruption-tolerant, since service-level agreements allow expressing and enforcing obligations regarding availability and quantified disruptions. This approach has been implemented on the OSGi service platform and iPOJO, a service-oriented component model for OSGi. iPOJO service dependency management has been extended in order to support our policy. The latter was validated both in the context of ambient intelligence, and on open-source and OSGi-based JOnAS application server.
The increasing popularity of employing web services for distributed systems contributes to the significance of service discovery. However, duplicated and similar functional features existing among services require service consumers to include additional aspects to evaluate the services. Generally, the service consumers would have the different view on the quality of service (QoS) of service attributes. How to select the best composite service in theory among available service (WS) candidates for consumers is an interesting practical issue. This work proposes a QoS-aware service selection model based on fuzzy linear programming (FLP) technologies, in order to identify their dissimilarity on service alternatives, assist service consumers in selecting most suitable services with consideration of their expectations and preferences. This approach can obtain the optimal solution of consensual weight of QoS attribute and Fuzzy Positive Ideal Solution (FPIS) by extending LINMAP method, developed by Srinivasan and Shocker. Finally, two numerical examples are given to demonstrate the process of QoS-aware web service selection. The experimental results demonstrated that it is a feasible and supplementary manner in selecting the of web services
Many Software's that share same or similar functional properties; so it is often a challenging effort to select credible and optimal software based on their various history QoS records. In view of this challenge, a novel QoS-aware software selection method based on service credibility evaluation is put forward, based on credibility evaluation associated with negotiated QoS dimensions. More specifically, the historical empirical data, execution logs and customer reviews of software, are used for evaluation purpose.
SLA (Service level agreement) is defined by an organization to fulfil its
client requirements, the time within which the deliverables should be turned
over to the clients. Tracking of SLA can be done manually by checking the
status, priority of any particular task. Manual SLA tracking takes time as one
has to go over each and every task that needs to be completed. For instance,
you ordered a product from a website and you are not happy with the quality of
the product and want to replace the same on urgent basis, You send mail to the
customer support department, the query/complaint will be submitted in a queue
and will be processed basis of its priority and urgency (The SLA for responding
back to customers concern are listed in the policy). This online SLA tracking
system will ensure that no queries/complaints are missed and are processed in
an organized manner as per their priority and the date by when it should be
handled. The portal will provide the status of the complaints for that
particular day and the ones which have been pending since last week. The
information can be refreshed as per the client need (within what time frame the
complaint should be addressed).
The “Cloud Computing” paradigm is gaining ground with new IT service providers and traditional IT out-sourcing providers alike. Customers want to use cloud computing solutions with all their advertised advantages and without the hassle of traditional long term outsourcing migration and contracting. Risk is at the center of attention when dealing with the adoption of cloud services. Because of the security concerns and the consequential reservations towards the acceptance of public cloud computing platforms, a lot has been done to improve security and trust in these environments. However, most of the implementations and research regarding this issue is concerning technical security risks with a focus on preventing perimeter-based attacks. Security and trust issues beyond perimeter based security risks have gained little attention. This paper identifies the need to look beyond technical issues and turns the attention to improving compliance and governance in cloud environments. In this process the focus is set on the discontinuity cap between existing methods to identify and evaluate IT risks and the treatment of these risks with Service Level Agreements. To close this cap a model for a dynamic view on current IT risk is proposed to comply with modern IT environments that are composed of an ampleness of different services. The model has a strong corporate context and will help companies to evaluate their current risk exposure and thus make better decisions when choosing their services.
The management of Quality of Service (QoS) in Information Systems allows their users to request services under certain conditions
varying in function of their requirements but also in function of the current capabilities of the computing environment. The
kind of the requirements and the notation used to formulate them vary with regards to application area and computing environment
used. This paper presents a generic architecture that can manage QoS independently of the QoS domain and of the distributed
environment used. We also introduce a QoS meta model (defined with a meta modeling facility – the so-called MOF – standardized
by OMG) to exchange QoS models that allows a generic approach for QoS notation. By this way, this QoS management architecture
is the first and only one platform which can manage all QoS contract properties (which are guaranty, observation, negotiation
and composition) under a generic approach with regards of domain, environment and notation.
Increasingly, services such as E-commerce, Web hosting,
application hosting, etc., are being deployed over an infrastructure
that spans multiple control domains. These end-to-end services require
cooperation and internetworking between multiple organizations, systems
and entities. Currently, there are no standard mechanisms to share
selective management information between the various service providers
or between service providers and their customers. Such mechanisms are
necessary for end-to-end service management and diagnosis as well as for
ensuring the service level obligations between a service provider and
its customers or partners. In this paper we describe an architecture
that uses contracts based on service level agreements (SLA) to share
selective management information across administrative boundaries. We
also describe the design of a prototype implementation of this
architecture that has been used by us for automatically measuring,
monitoring, and verifying service level agreements for Internet services
Today's computing environments are becoming more and more distributed in nature. At the same time, the applications used in these environments are becoming more complicated and are being used in more mission critical roles in the enterprise. Consequently, users' demands for performance, reliability, and availability, and availability are increasing rapidly. To meet these needs, a high level of quality of service must be delivered to the user. Doing so, however, is not an easy task. Because of considerable research effort into this area, great strides are being made towards acceptable quality of service solutions. As researchers in this area have recognized, there are still many challenging open problems needing to be addressed. One of the more interesting, yet difficult challenges is the specification of quality of service-quality of service solutions must handle quality of service specifications as application-level expectations, as opposed to low-level resource reservations. Doing so, however, has been proven to be a non-trivial task. To address this problem, we have developed an application-driven approach to resource management to support quality of service. We present our general strategy, the design of a solution realizing this approach, and a preliminary prototype implementation based on this architecture. We describe experimentation and experience to date and evaluate our work and its effectiveness based on these preliminary results. Finally, we conclude with a summary of our work and outline our plans to evolve it in the future.
Increasingly, Internet services are being deployed over an infrastructure that spans multiple control domains. These services require cooperation between multiple organizations, systems and entities. Currently, few standard mechanisms exist to share selective management information between the various service providers or between service providers and their customers. Such mechanisms are necessary for end-to-end service management and diagnosis as well as for ensuring the service level obligations between a service provider and its customers or partners. This paper describes an architecture that uses contracts based on service level agreements (SLAs) to share selective management information across administrative boundaries. The design of a prototype implementation for automatically measuring, monitoring, and verifying service level agreements for Internet services is also described.
Due to the requirements of open service markets, the structure of networks and application systems is changing. To handle the evolving complex distributed systems, new concepts for an efficient management of such systems have to be developed. Focussing on the service level, examples for existing concepts are trading, to find services in a distributed environment, and load balancing, to avoid performance bottlenecks in service provision. This paper deals with the integration of a trader and a load balancer. The allocation of client requests to suitable servers is adaptable depending on the current system usage and thus the quality of the services used is increased in terms of performance. The approach used is independent of the servers’ characteristics, as no provision of additional service properties to cover load aspects is necessary for the servers involved. Furthermore, it may be flexibly enhanced, as the concept of ‘load’ used can be varied without modification of trader or load balancer. This approach was implemented and evaluated in several scenarios.
Traditional object-oriented design methods deal with the functional aspects of systems, but they do not address quality-of-service (QoS) aspects, such as reliability, availability, performance, security and timing. However, deciding which QoS properties should be provided by individual system components is an important part of the design process. Different decisions are likely to result in different component implementations and system structures. Thus, decisions about component-level QoS should commonly be made at design time, before the implementation is begun. Since these decisions are an important part of the design process, they should be captured as part of the design. We propose a general quality-of-service specification language, which we call QML. In this paper we show how QML can be used to capture QoS properties as part of designs. In addition, we extend UML, the de facto standard object-oriented modelling language, to support the concepts of QML.
QML is designed to integrate with object-oriented features, such as interfaces, classes and inheritance. In particular, it allows specification of QoS properties through refinement of existing QoS specifications. Although we exemplify the use of QML to specify QoS properties within the categories of reliability and performance, QML can be used for specification within any QoS category - QoS categories are user-defined types in QML.
Sometimes, QoS characteristics and requirements change dynamically due to changing user preferences, or changes in the environment. For such situations static specification is insufficient. To allow for dynamic systems that change and evolve over time, we provide a QoS specification runtime representation. This representation enables systems to create, manipulate and exchange QoS information, and thereby negotiate and adapt to changing QoS requirements and conditions.
Commercial approaches to service level agreements (SLA) management
sometimes appear to be fragmented. In this sort of situation, a general
framework that subsumes piecemeal approaches does much good. We provide
a framework that may serve as a baseline against which one can situate
and evaluate SLA proposals. We provide (i) definitions which lead to the
broader concept of service level management (SLM), (ii) a general SLM
methodology, (iii) research challenges in SLM, and (iv) an SLM
architecture. As such, the paper is a tutorial paper concerning current
practices and outstanding issues in service level management
It is becoming increasingly commonplace for multiple applications
with different quality of service (QoS) requirements to share the
resources of a distributed system. Within this environment, the resource
management algorithms must take into account the QoS desired by
applications and the ability of the system resources to provide it. We
present a taxonomy for specifying QoS for the different components of a
distributed system, from the applications down to the resources. We
specify QoS as a combination of metrics and policies. QoS metrics are
used to specify performance parameters, security requirements and the
relative importance of the work in the system. We define three types of
QoS performance parameters: timeliness, precision, and accuracy. QoS
policies capture application-specific policies that govern how an
application is treated by the resource manager. Examples of such
policies are management policies and the levels of service. We explore
each of these components of the QoS taxonomy in detail
The efficient management of a quality level of Internet service is
becoming increasingly important to both customers and service providers.
This article describes how service level agreements for multimedia
Internet service can be managed and controlled. We first present a
literature survey on the problems of SLA management: SLA parameter
definition, SLA measurement, and QoS management. We present a utility
model to capture the management and control aspects of SLAs for
multimedia Internet service. This utility model has been used in
microeconomics theory, but here we have applied it to SLA management.
This model provides a computationally feasible solution for admission
control and quality adaptation for multimedia Internet service and SLA
management. It also allows management policies to be flexibly expressed
by service providers. Finally, we apply the utility model to the SLA
management of VoIP service and describe how to use it for admission
control, dynamic quality adaptation, and resource allocation for SLA
assurance
Over the past several years there has been a considerable amount of research within the field of quality of service (QoS) support for distributed multimedia systems. To date, most of the work has occurred within the context of individual architectural layers such as the distributed system platform, operating system, transport subsystem and network. Much less progress has been made in addressing the issue of overall end-to-end support for multimedia communications. In recognition of this, a number of research teams have proposed the development of QoS architectures which incorporate quality of service configurable interfaces and quality of service driven control and management mechanisms across all architectural layers. This paper examines the state-of-the-art in the development of QoS architectures. The approach taken is, initially, to present QoS terminology and a generalised QoSframeworkfor understanding and discussing quality of service in the context of distributed multimedia systems. Following this, we consider current research in the area of layer specific quality of service support, and then, evaluate a number of QoS architectures that have recently emerged in the literature from the telecommunications, computer communications and stan- dards communities.
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GB917, public evaluation version 1.5, June 2001.
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