Adaptive Stabilization of Reactive Protocols

Abstract

A self-stabilizing distributed protocol can recover from any state-corrupting fault. A self-stabilizing protocol is called adaptive if its recovery time is proportional to the number of processors hit by the fault. General adaptive protocols are known for the special case of function computations: these are tasks that map static distributed inputs to static distributed outputs. In reactive distributed systems, input values at each node change on-line, and dynamic distributed outputs are to be generated in response in an on-line fashion. To date, only some specific reactive tasks have had an adaptive implementation. In this paper we outline the first proof that all reactive tasks admit adaptive protocols. The key ingredient of the proof is an algorithm for distributing input values in an adaptive fashion. Our algorithm is optimal, up to a constant factor, in its fault resilience, response time, and recovery time.