Byzantine Fault Tolerance for Session-Oriented Multi-Tiered Applications

This article presents a lightweight Byzantine fault tolerance (BFT) framework for session-oriented multi-tiered applications. We conclude that it is sufficient to use a lightweight BFT algorithm instead of a traditional BFT algorithm, based on a comprehensive study of the threat model to, and the state model of, the session-oriented multi-tiered applications. The lightweight BFT algorithm uses source ordering, rather than total ordering, of incoming requests to achieve Byzantine fault tolerant state-machine replication of such type of applications. The performance of the lightweight BFT framework is evaluated using a shopping cart application prototype built on the web services platform. The same shopping cart application is used as a running example to illustrate the problem we address and our proposed solution. Performance evaluation results obtained from the prototype implementation show that indeed our lightweight BFT algorithm incurs very insignificant overhead.