Impossibility of distributed consensus with one faulty process

The consensus problem involves an asynchronous system of processes, some of which may be unreliable. The problem is for the reliable processes to agree on a binary value. In this paper, it is shown that every protocol for this problem has the possibility of nontermination, even with only one faulty process.

By way of contrast, solutions are known for the synchronous case, the “Byzantine Generals” problem.