QoS integration in Web services with the WS-QoS framework
Min Tian · Universitätsbibliothek der FU Berlin Hochschulschriftenstelle u. Dokumentenserver · 2005
Web Services are becoming more and more popular these days and more and more businesses are planning to build their future solutions on Web service technology. By now, SOAP and WSDL have become reliable standards in the field of Web service execution. While the concept of UDDI allows for automatic discovery of services implementing a common public tModel interface, there have been only few attempts to find a standardized form to describe the quality of service (QoS) with which services are executed. The need for QoS specifications in Web services is driven by two demands. Clients aim to experience a good service performance, e.g. low waiting time, high reliability, and availability to successfully use the service whenever the need arises. On the other hand, when it comes to e-business, service providers need to formulate QoS-aware offers in order to gain the highest possible profit from their business. Examples are high throughput guarantees and low response time through dynamic capacity allocation, resource allocation, and load balancing in order to serve a high number of clients with assured QoS. Moreover, crucial transactions such as payment should experience prioritized execution realized by transaction differentiation. Service providers will strive to find an optimal relation between user satisfaction and system utilization. There are sophisticated technologies to actively differentiate between various QoS levels both on the transport level (DiffServ, IntServ, classes of services in UMTS and ATM, etc.) and on the server level (load balancing, transaction differentiation, HTTP request differentiation, etc.), yet there are no standardized means to describe the desired QoS on the application level. In terms of the Internet model, the Web services can be placed between the application and network layer. To close the gap between the Web Services layer and the underlying QoS-aware transport technologies, we have developed the Web services-QoS architecture (WS-QoS). The main motivations of our work are designing an architecture that allows both service clients and service providers to specify requests and offers with QoS properties and QoS classes, enabling an efficient service offer selection in order to accelerate the overall lookup process for the client, providing a flexible way for service providers to publish and update their service offers with different QoS aspects as well as mapping the QoS requirements regarding the underlying transport network from the higher (Web service and application) layer onto the actual underlying network technology at runtime in order to achieve an overall QoS support through the different layers in terms of the Internet model. The main contributions of this work are the WS-QoS architecture that enables QoS-aware service specifications, the broker based Web service selection model that enables an efficient QoS-aware service selection as well as the QoS mapping guarantying the assured QoS.