Computing, Observing, Controlling, Checkpointing: Symbiosis Is Even Better Than Agreement!

Abstract

This talk is a tribute to Michel Raynal, and more precisely to the nice work I had the great pleasure to share with him during twenty years of close collaboration (1985-2004).

Why this title “Symbiosis is better than Agreement”? Despite the famous FLP (1985) impossibility result, Michel and I often succeeded to reach agreement. Perhaps none of us was faulty? Perhaps our context was not as asynchronous as it could appear? Well, I don’t believe so! The deep reason lies rather in the symbiosis that prevailed between Michel (a tree) and me (a mushroom). This symbiosis not only allowed us to reach agreement, but, more interestingly, to obtain important and fundamental results in several fields of distributed computing. From “old” problems or paradigms - e.g. Network traversal, Detection of stable properties, Election of a leader,Mutual exclusion, Distributed evaluation - to advances in new ones - e.g., related to fault tolerance such as Checkpointing -, we have always strived to bring out design principles and to obtain generic solutions.