A Novel Approach for Efficient Resource Utilization and Trustworthy Web Service

Many Web services are expected to run with high degree of security and dependability. Toachieve this goal, it is essential to use a Web-services compatible framework that tolerates notonly crash faults, but Byzantine faults as well, due to the untrusted communication environment inwhich the Web services operate. In this paper, we describe the design and implementation ofsuch a framework, called RET-WS (Resource Efficient and Trustworthy Execution -WebService).RET-WS is designed to operate on top of the standard SOAP messaging framework formaximum interoperability with resource efficient way to execute requests in Byzantine-faulttolerantreplication that is particularly well suited for services in which request processing isresource-intensive. Previous efforts took a failure masking all-active approach of using allexecution replicas to execute all requests; at least 2t + 1 execution replicas are needed to mask tByzantine-faulty ones. We describe an asynchronous protocol that provides resource-efficientexecution by combining failure masking with imperfect failure detection and checkpointing. It isimplemented as a pluggable module within the Axis2 architecture, as such, it requires minimumchanges to the Web applications. The core fault tolerance mechanisms used in RET-WS arebased on the well-known Castro and Liskov's BFT algorithm for optimal efficiency with somemodification for resource efficient way. Our performance measurements confirm that RET-WSincurs only moderate runtime overhead considering the complexity of the mechanisms.