On the minimal synchronism needed for distributed consensus

Reaching agreement is a primitive of distributed computing. While this poses no problem in an ideal, failure-free environment, it imposes certain constraints on the capabilities of an actual system: a system is viable only if it permits the existence of consensus protocols tolerant to some number of failures. Fischer, Lynch and Paterson [FLP] have shown that in a completely asynchronous model, even one failure cannot be tolerated. In this paper we extend their work, identifying several critical system parameters, including various synchronicity conditions, and examine how varying these affects the number of faults which can be tolerated. Our proofs expose general heuristic principles that explain why consensus is possible in certain models but not possible in others.

[1]  Michael Ben-Or,et al.  Another advantage of free choice (Extended Abstract): Completely asynchronous agreement protocols , 1983, PODC '83.

[2]  Nancy A. Lynch,et al.  Impossibility of distributed consensus with one faulty process , 1983, PODS '83.

[3]  Leslie Lamport,et al.  Reaching Agreement in the Presence of Faults , 1980, JACM.

[4]  Nancy A. Lynch,et al.  Impossibility of distributed consensus with one faulty process , 1985, JACM.

[5]  Danny Dolev,et al.  Polynomial algorithms for multiple processor agreement , 1982, STOC '82.

[6]  Journal of the Association for Computing Machinery , 1961, Nature.

[7]  Michael Ben-Or,et al.  Fast asynchronous Byzantine agreement (extended abstract) , 1985, PODC '85.

[8]  Danny Dolev,et al.  Authenticated Algorithms for Byzantine Agreement , 1983, SIAM J. Comput..

[9]  Michael O. Rabin,et al.  Randomized byzantine generals , 1983, 24th Annual Symposium on Foundations of Computer Science (sfcs 1983).

[10]  Danny Dolev,et al.  'Eventual' is earlier than 'immediate' , 1982, 23rd Annual Symposium on Foundations of Computer Science (sfcs 1982).

[11]  Sam Toueg,et al.  Randomized Byzantine Agreements , 1984, PODC '84.

[12]  Gabriel Bracha,et al.  An asynchronous [(n - 1)/3]-resilient consensus protocol , 1984, PODC '84.

[13]  Hagit Attiya,et al.  Asynchronous Byzantine consensus , 1984, PODC '84.

[14]  Sam Toueg,et al.  Resilient consensus protocols , 1983, PODC '83.

[15]  Michael Ben-Or,et al.  Another advantage of free choice (Extended Abstract): Completely asynchronous agreement protocols , 1983, PODC '83.

[16]  Leslie Lamport,et al.  The Byzantine Generals Problem , 1982, TOPL.