Different Perspectives on FLP Impossibility

Abstract

We demonstrate termination of binary consensus under the model and conditions used by Fischer, Lynch, and Patterson (FLP) to prove impossibility of binary agreement - in complete asynchrony and a possible process crash - in two steps. First, we introduce a new paradigm for consensus termination and show that impossibility of agreement is not evidence for impossibility to terminate. Next, we present a consensus algorithm that ensures termination with agreement about the initial input from the processes.