ReliableWeb Services: Methodology, Experiment and Modeling

We identify parameters impacting Web services dependability, describe the methods of dependability enhancement by redundancy in space and redundancy in time, and perform a series of experiments to evaluate the availability of Web services. To increase the availability of Web services, we employ several replication schemes and compare them with a single service. The Web services are coordinated by a replication manager. It provides a round robin algorithm for scheduling the workload of the Web services and keeps updating the availability of each Web service. The replication algorithm and the detailed system configuration are described. Experiments are performed to evaluate the resulting service availability. Modeling on the Web services with Petri-net is constructed and verified through experiments with different applications. With the parameters obtained from the experiments, the proposed model can be engaged to demonstrate the characteristics of the Web service.