Quality Of Service Broker Research Articles

QoS Broker based Architecture for Dynamic Web Service Discovery and Composition

With the widespread proliferation of web services, the demand on highly reliable and available services increases to satisfy business and personal needs. As the number of functionally similar web service increases on the Internet, Quality of Service (QoS) based web service selection and composition has gained much attention. However, the existing architectures for runtime service composition requires discovery of all functionally similar services, which consumes too much time. Instead, it can be possible to discover only those services which are highly reliable and thus included in composition. This issue can be solved by introducing a broker based architecture for automated dynamic web service discovery and composition in which the composition operation accepts as input a set optimized services along with their QoS specifications. The proposed architecture is able to reduce the composition time by performing optimized selection of services using Local Selection and Local Optimization (LSLO) approach during service composition. The architecture is fault tolerant and ensures improved reputation prediction accuracy of selected services using Mixed Opinion based Reputation Prediction (MORP) approach. In this paper, a comparative analysis is also performed on the basis of set of criterion to analyze the existing dynamic web service discovery and composition architectures for their strengths and weaknesses.

Estimation of Always Best Connected Network in Heterogeneous Environment Based on Prediction of Recent Call History and Call Blocking Probability

Presently, the emergence of 4G heterogeneous network has attracted most of the user centric applications like video chatting, online mobile interactive classroom besides voice services. To facilitate such bandwidth hungry multimedia applications and to ensure QoS (Quality of Service), Always Best Connected (ABC) network is to be selected among available heterogeneous network. The selection of the ABC network is based on certain design parameters such as cost factor, bandwidth utilization, packet delivery ratio, security, throughput, delay, packet loss ratio and call blocking probability. In this paper, all the above mentioned design parameters are considered to evaluate the performance of Always Best Connected network under heterogeneous environment for mobile users. In addition, to select Always Best Connected network in a heterogeneous environment, a novel parameter namely recent call history-‘rch' is proposed to predict the call blocking probability (Cbp) of a network.The estimation of ‘rch' parameter in terms of Cbp avoids unnecessary hand-off and enhances the effective bandwidth utilization of a cellular network under heavy load condition.A QoS mapper submodule is proposed in the QoS broker module to predict the ‘rch' parameter of a network to select an optimum network. Further, a statistcal model based on Bayesian network using the data on recent call history is applied for Cbp estimation and simulated over various heterogeneous environment condition. The simulated results show improved performance of user centric applications when compared with non-predictive methods.

A Quality of Service Broker Based Process Model for Dynamic Web Service Composition

Problem statement: With fast spreading of web services technology ove r the Internet, the quality aspects of a web service has received signi ficant attention to the practitioners. The quality of web service includes both functional and nonfunctio nal details. In order to provide the correct and meaningful information to web service consumer, sometimes there is a need to compose existing web services in order to create new web service. Approach: We have proposed a Quality of Service (QoS) broker based process model for Dynamic Web Service Composition (DWSC). The QoS broker in the proposed model is responsible for web servic e collection, selection, optimization and composition based on the service consumer's require ments. It also verifies and certifies the functiona l and QoS specifications provided by service provider at the time of web service registration before publishing it in Universal Description, Discovery a nd Integration (UDDI) registry. The detailed working of QoS broker is also presented in the stud y with functionality of each component. We will also discuss the process flowchart for new web serv ice registration and web service composition at runtime. Results: The proposed QoS broker based model for dynamic web service composition solves the problems associated with quality of web service. It also prevents the central repository from malicious service provider to publish wrong in formation. Conclusion: The QoS broker-based process model for dynamic web service composition guarantees the quality of delivered service to web service consumers and improve the efficiency of composition.

Dynamic selection mechanism for quality of service aware web services

A web service is an interface of the software component that can be accessed by standard Internet protocols. The web service technology enables an application to application communication and interoperability. The increasing number of web service providers throughout the globe have produced numerous web services providing the same or similar functionality. This necessitates the use of tools and techniques to search the suitable services available over the Web. UDDI (universal description, discovery and integration) is the first initiative to find the suitable web services based on the requester's functional demands. However, the requester's requirements may also include non-functional aspects like quality of service (QoS). In this paper, the authors define a QoS model for QoS aware and business driven web service publishing and selection. The authors propose a QoS requirement format for the requesters, to specify their complex demands on QoS for the web service selection. The authors define a tree structure called quality constraint tree (QCT) to represent the requester's variety of requirements on QoS properties having varied preferences. The paper proposes a QoS broker based architecture for web service selection, which facilitates the requesters to specify their QoS requirements to select qualitatively optimal web service. A web service selection algorithm is presented, which ranks the functionally similar web services based on the degree of satisfaction of the requester's QoS requirements and preferences. The paper defines web service provider qualities to distinguish qualitatively competitive web services. The paper also presents the modelling and selection mechanism for the requester's alternative constraints defined on the QoS. The authors implement the QoS broker based system to prove the correctness of the proposed web service selection mechanism.

The Design of QoS Broker Algorithms for QoS-Capable Web Services

QoS (quality of service) support in Web services is an important issue since it ensures service usability and utility for each client and, in addition, improves server utilization. In this article, we present a QoS-capable Web service architecture, QCWS, by introducing a QoS broker module between service clients and providers (servers). The functions of the QoS broker module include tracking QoS information about servers, making selection decisions for clients, and negotiating with servers to get QoS agreements. We study two resource allocation algorithms (HQ and RQ) used by QoS brokers acting as the front-end of servers. The goals of the algorithms are to maximize the server resource usage while minimizing the QoS instability for each client. The first algorithm, HQ, assigns a homogeneous service level to all clients on the system and adjusts the service level according to the number of active clients. The second algorithm, RQ, assigns different service levels to clients according to their needs. Both algorithms try to minimize the resource reallocations for existing clients. The QoS performance and instability trade-offs are studied by simulation.

Design, implementation, and experiences of the OMEGA end-point architecture

The OMEGA architecture provides end-to-end quality-of-service (QoS) guarantees for distributed applications. QoS parameters are translated between application and network requirements by the QoS broker, thus integrating media and network QoS management into a single entity. Admission control uses a schedulability test derived from application requirements. A novel task priority and precedence-based scheme is used to represent complex application requirements and ensure correct feasible schedules. A prototype of OMEGA has been implemented using workstations connected by a 155 Mb/s dedicated ATM local-area network (LAN). To simplify implementation, we assumed networked multimedia application with periodic media streams, specifically a master/slave telerobotics application. This application employs media with highly diverse QoS requirements (e.g., interarrival times, loss rate, and bandwidth) and therefore provides a good platform for testing how closely one can achieve QoS guarantees with workstation hosts and cell-switching. Experience with this implementation has helped to identify new challenges to extending these techniques to a larger domain of applications and systems, and suggests promising new research questions.