Managing web service quality

Now-a-days the web services are uprising technology which appeals lots of attention from both academic and industry. The quality of service has been one of the major challenges in the web services. If the web services become operational then the service providers with Service Level Agreement (SLA) need to consider and monitor with respect to the quality of web services and SLA. The most important factor is that to monitor and prevent the SLA intrusion in the composite web services. In the existing work the adaptation is done only at the instance level of the composition, for each level of composition the adaptation is done in each instance. Then the aggregated SLO's are defined over the number of instances which are out of scope and also the adaptation is not considered as permanent. In this PERvent (prediction and prevention based on event monitoring) framework is not supported for large number of adaptation action per the checkpoint because it is fully based on the number of checkpoints, and also it supports limited structural adaptation in the composition. The proposed work is to exclude these drawbacks by introducing the framework called Quality based dynamic composition (QDC) framework for monitoring the SLA parameter as well as monitoring Service Quality (QOS) Parameter for composite web service and also we will discuss the experimental results to prove how these approaches to monitor the Quality of Service (QOS) parameters for the composed web service.

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.

Service level agreement (SLA) is a formal contract between a service provider and a service consumer to guarantee the Quality of service (QoS) expectations, it is used in all areas of information technology, such as Cloud Computing, Internet of Things (IoT), networks and Web services. For IoT applications, the main challenges are: (1) how to describe the SLA terms, such as QoS properties, service levels, penalties in SLA violation, (2) how to monitor these terms, and (3) how to integrate an SLA into all the IoT application layers. Therefore, in this paper, we propose ML-SLA-IoT, a framework for SLA specification and monitoring. It covers the entire layers of an IoT application. It describes precisely QoS levels, provided services, and obligations. It differs from other SLA specification languages in the specification of user preferences, the use of microservices (for reusability, dynamism and ease of integration) and ML-SLA (multi-level metrics and QoS according to existing constraints and user preferences). Furthermore, ML-SLA-IoT monitors SLA terms in an automatic and decentralised manner using smart contracts and blockchain technologies without the intervention of the third-party. Finally, we present a comparative study and experiments with existing solutions regarding to some criteria for SLA specification and monitoring. Our results show that ML-SLA-IoT gives better performance in terms of dynamic pricing, obligation combination, and SLA monitoring.

Today, the service computing research is focusing on providing efficient solutions to the challenges of the future Internet applications. The major difference that is created by these applications is their ubiquitous on-the-move availability as cloud services. This means that the mobility is rapidly becoming a fundamental requirement of the future. In addition to that, the integration of mobile and service computing domains has enabled the existing mobile devices to offer their resources as mobile Web Services (WS). For this reason, the provisioning of mobile WS in future networks is expected to become a part of the cloud, where ubiquitous services are offered by any device. This will open new business prospects for the service providers. In this paper, we present the concept of protecting such mobile WS by using Service Level Agreements (SLA) on mobile devices. Here, we propose a framework to offer SLA negotiations and manage the Quality of Service (QoS) of the provisioned mobile WS. Furthermore, the paper explains the four primary architectural components and classifies their functions into four fundamental SLA life cycles. Also, the detailed discussion regarding each life cycle and its relation to the corresponding component(s) is provided. The research addresses some major issues of authentic and authorized access to mobile WS that might become useful as we move towards the future ubiquitous Internet.

A service level agreement (SLA) is a service contract that includes the evaluation criteria for agreed service quality standards. Since agreeable specifications on the evaluation criteria cannot be limited in practice, competitive SLA management products must be extensible in terms of their support for contract-specific SLA compliance evaluations. While the need of running and managing those software products as services increases, we have found that developing a good solution for configuring them as per contractual terms is a challenging task. This paper presents the Fresco framework, which facilitates configuring extensible SLA management systems using Web services. An XML-based specification of SLA management related data called SCOL will also be presented to show how the framework supports contract-specific SLA terms and contract-specific extensions of the deployed SLA management software. The paper furthermore shows how the Fresco system uses a template-based approach to communicate with other Web services applications with support for various input and output formats. Our experience with implementing the Fresco framework for a leading commercial SLA management software product demonstrates that the framework facilitates the creation of effective and efficient solutions for configuring extensible SLA management systems.

Managing Service Level Agreement (SLA) for composite semantic web services is a very complex process, as it involves many complex tasks such as components discovery, provisioning, monitoring, recovery, and coordination. Indeed, managing all these tasks manually is a very cumbersome operation, nevertheless it is time consuming and prone to errors. To overcome such problems, automated SLA management for composite semantic web services is needed. This requires the SLA of the composite service to be described in a machine-understandable format such that it can be understood and processed by the automated SLA management tool. Currently, there is no SLA description language for composite semantic web services, but there exists an SLA description language for atomic web services, known as the Web Service Level Agreement (WSLA). Hence, in this paper, we aim to extend the WSLA language to describe composite semantic web services' SLAs, then we show how we can automatically generate the components' SLAs from the composite semantic web services' SLAs; adopting the CRECENT framework that we previously proposed for managing composite web services.

An Service Level Agreement (SLA) is a contract between service provider and consumer, and includes appropriate actions to be taken upon violation of the contractual obligations. To ensure the negotiation on an SLA is reasonable by reference the measured history data. The paper proposes a feasible Web Service Level Agreement (WS-SLA) Establishing Framework, which can flexible define trustable SLA requirements and penalties actions upon service providers based on monitoring data from service consumer. Web service QoS (WS-QoS) Monitor provides the automatic approach for measureing Quality of Service (QoS) parameters from service requester side. WS-SLA Editor allows service consumer to flexible define their SLA requirement and penalties actions upon service providers.

A Service Level Agreement (SLA) is a legal contract between parties to ensure the Quality of Service (QoS). It specifies one or more service level objectives (SLO), to ensure that the QoS delivered has met customer expectations. However, It becomes hard to guarantee QoS levels and detect SLA violations. Therefore, we propose to use MDE (Model Driven Engineering) to express the SLA contract requirements. This latter, created with a specific modeling language (DSML), will be used harmonically with a Multi-agent systems (MASs) in order to monitor SLA violations in real-time. Indeed, MASs are suitable tools for self-detection of failures and self-monitoring of cloud operations and services, QoS negotiation and SLA management. They are designed to operate in a dynamically changing environment. Our main motivation is firstly to use MDE technology for the creation of the SLA contract and then to integrate MASs in order to control the quality of service contract and guarantee transparency and symmetry with respect to the SLA contract between prospective signatories.

A service level agreement (SLA) is part of a contract between a cloud service provider (CSP) and a cloud service user (CSU) which defines and describes different agreed properties of the service. The negotiation of the SLA between a CSU and a CSP is a pivotal process in the SLA life cycle. An SLA may include many negotiable quality of service (QoS) parameters with each QoS parameter having multiple acceptable values. Different combinations of acceptable values for all QoS parameters grow exponentially as number of QoS parameters and their selectable values increase. Manually negotiating for all of the QoS parameters considering their various options can be an erroneous and diligent task with lower utility. In this paper, a time efficient flip-flop negotiation strategy for the SLAs in cloud services is presented. The flip-flop negotiation strategy is based on a time dependent 3D utility function and on a dynamic concession strategy using the polynomial extrapolation of opponent's concession. This negotiation strategy is useful for time-critical cloud services as it operates with a motive of reaching an agreement at earlier time without compromising over the utility level of the agreement. Moreover, a multi-provider concurrent negotiation method is presented in this work using the flip-flop negotiation strategy. Multiple experiments are performed (using the implementation of flip-flop negotiation strategy) to test the presented work. The results of the experiments enforce the validity of the flip-flop negotiation strategy for such cloud services where time is an important factor during the SLA negotiation process.

With the advent of 5G technology, we are witnessing the development of increasingly bandwidth-hungry network applications, such as enhanced mobile broadband, massive machine-type communications and ultra-reliable low-latency communications. Software Defined Networking (SDN), Network Function Virtualization (NFV) and Network Slicing (NS) are gaining momentum not only in research but also in IT industry representing the drivers of 5G. NS is an approach to network operations allowing the partition of a physical topology into multiple independent virtual networks, called network slices (or slices). Within a single slice, a set of Service Function Chains (SFCs) is defined and the network resources, e.g. bandwidth, can be provisioned dynamically on demand according to specific Quality of Service (QoS) and Service Level Agreement (SLA) requirements. Traditional schemes for network resources provisioning based on static policies may lead to poor resource utilization and suffer from scalability issues. In this article, we investigate the application of Reinforcement Learning (RL) for performing dynamic SFC resources allocation in NFV-SDN enabled metro-core optical networks. RL allows to build a self-learning system able to solve highly complex problems by employing RL agents to learn policies from an evolving network environment. In particular, we build an RL system able to optimize the resources allocation of SFCs in a multi-layer network (packet over flexi-grid optical layer). The RL agent decides if and when to reconfigure the SFCs, given state of the network and historical traffic traces. Numerical simulations show significant advantages of our RL-based optimization over rule-based optimization design.

Service level agreement (SLA) in cloud computing can be defined as a contractual agreement signed between cloud user and cloud provider in order to manage the quality of service (QoS) parameters which are the fundamental part of SLAs. The current dynamic SLA monitoring approaches have considered the cloud provider's perspective only. To take into consideration the user's perspective; this research proposes a dynamic SLA monitoring approach by generating new SLA terms based on analysing the SLA penalties. A new proposed trade-off mechanism is applied between monthly cost and QoS guarantee values. Thus; we propose a dynamic model for updating QoS parameters of SLA in cloud environment. Java language is used with a QoS measurement dataset to experiment the proposed approach. The current Static SLA (SSLA) approaches are compared with the proposed Dynamic SLA (DSLA) approach. The results of this experimental study show that the number of SLA violations in DSLA are less than the number of SLA violations in SSLA.

Service level agreement (SLA) in cloud computing can be defined as a contractual agreement signed between cloud user and cloud provider in order to manage the quality of service (QoS) parameters which are the fundamental part of SLAs. The current dynamic SLA monitoring approaches have considered the cloud provider's perspective only. To take into consideration the user's perspective; this research proposes a dynamic SLA monitoring approach by generating new SLA terms based on analysing the SLA penalties. A new proposed trade-off mechanism is applied between monthly cost and QoS guarantee values. Thus; we propose a dynamic model for updating QoS parameters of SLA in cloud environment. Java language is used with a QoS measurement dataset to experiment the proposed approach. The current Static SLA (SSLA) approaches are compared with the proposed Dynamic SLA (DSLA) approach. The results of this experimental study show that the number of SLA violations in DSLA are less than the number of SLA violations in SSLA.

This work presents a novel scheme for Service Level Agreements (SLAs) in a service-oriented architecture (SOA). An SLA is a contract that guarantees quality of service (QoS) between service providers and consumers. An SLA can be split into several parts for an SOA system which is consisting of different services. A split SLA is used to guarantee quality of services for one of services in an SOA system. However, these contract rules do not regulate follow-up process in services. SLA violations may occur consequently. For instance, interactions between services are not encrypted because the encryption parameter isn't included in the split SLA contract. Confidential data would be transmitted through unsafe channels. There would be a security issue of SLA Management for follow-up processes in an SOA system. The novel scheme in this work addresses these problems. Using SLAs management proposed in this work can identify the services that consumer needs and split the contracts for follow-up services. SLAs are not only guaranteed between service providers and consumers but also assured in follow-up processes. The proposed method improves the security and completeness of SLA using in an SOA system.

The way Internet is used changes: demand grows for critical services that cross several provider networks; guaranteeing a required end-to-end quality of service (QoS) across several networks becomes a challenge. Some critical services (e.g. video-conference, VPN etc.) can not be satisfied in a best effort fashion. The use of QoS contracts (service level agreements, SLAs) is effective for management of such services. However, the problem of meeting end-to-end QoS requirement remains: no centralized entity can compute overall QoS for chains of contracts, and a fortiori, such contract chains can not be optimized centrally. Thus, the following problem has to be solved: given an end- to-end QoS request and collections of available SLAs on each participating domain, establish an end-to-end contract committing a chain of providers and giving optimal service under most reliable guarantees available.

Utility computing enables the use of computational resources and services by consumers with service obligations and expectations defined in Service Level Agreements (SLAs). Parallel applications and workflows can be executed across multiple sites to benefit from access to a wide range of resources and to respond to dynamic runtime requirements. A utility computing provider has the difficult role of ensuring that all current SLAs are provisioned, while concurrently forming new SLAs and providing multiple services to numerous consumers. Scheduling to satisfy SLAs can result in a low return from a provider's resources due to trading off Quality of Service (QoS) guarantees against utilisation. One technique is to employ advance reservations so that an SLA aware scheduler can properly manage and schedule its resources. To improve system utilisation we exploit the principle that some consumers will be more flexible than others in relation to the starting or completion time, and that we can juggle the execution schedule right up until each execution starts. In this paper we present a QoS scheduler that uses SLAs to efficiently schedule advance reservations for computation services based on their flexibility. In our SLA model users can reduce or increase the flexibility of their QoS requirements over time according to their needs and resource provider policies. We introduce our scheduling algorithms, and show experimentally that it is possible to use flexible advance reservations to meet specified QoS while improving resource utilisation.