Boosting system performance with optimistic distributed protocols

Optimistic distributed protocols can dramatically improve system performanc e if the underlying system assumptions are sound and carry a high degree of probability. Optimistic protocols aggressively execute actions based on best-case system assumptions. Using optimistic protocols unquestionably involves tradeoffs, but if a protocol is well designed and the optimistic assumptions hold fre quently enough, the gain in performance outweighs the overhead of repairing actions that execute incorrectly. Demand for high performance under special circumstances in distributed sett ings has led to the development of optimistic distributed protocols in rece nt years. Indeed, given the right optimistic assumptions and mechanisms, op timistic protocols can significantly boost the efficiency of a system. Desi gning such protocols, however, is still a complicated and poorly understood activity. Part of this complexity is due to the inherent complications of distributed protocols and part is due to the lack of knowledge about how op timistic protocols should work. By providing a framework to reason about th ese protocols, this article is a first step toward systematizing the constr uction of optimistic distributed protocols. However, much still remains to be understood about how to design their underlying mechanisms.