Abstract
Abstract We consider the Byzantine consensus problem in a partially synchronous system with strong validity. For this problem, two main algorithms—with different resilience—are described in the literature. These two algorithms assume a leader process. A decentralized variant (variant without leader) of these two algorithms has also been given in a previous paper. Here, we compare analytically, in a round-based model, the leader-based variant of these algorithms with the decentralized variant. We show that, in most cases, the decentralized variant of the algorithm has a better worst-case execution time. Moreover, for the practically relevant case t≤2 (where t is the maximum number of Byzantine processes), this worst-case execution time is even at least as good as the execution time of the leader-based algorithms in fault-free runs.
Highlights
Consensus is a fundamental building block for fault-tolerant distributed systems
Algorithms for solving the consensus problem can be classified into two broad categories: leaderbased algorithms that use the notion of a leader, and decentralized algorithms, where no such dedicated process is used
Most of the consensus algorithms proposed in early 80s, for both synchronous and asynchronous systems,1 are decentralized (e.g., [2, 11, 14, 15])
Summary
Consensus is a fundamental building block for fault-tolerant distributed systems. Algorithms for solving the consensus problem can be classified into two broad categories: leaderbased algorithms that use the notion of a (changing) leader (a process with some specific role), and decentralized algorithms, where no such dedicated process is used. The second question is to analyze the worst-case performance of the leader-based algorithm and the decentralized algorithm in terms of (i) number of rounds and (ii) in terms of execution time. This work is motivated by the results of Amir et al [1] and Clement et al [6] These two papers have pointed out that the leader-based PBFT Byzantine consensus algorithm [4] is vulnerable to performance degradation. Our paper analyzes two Byzantine consensus algorithms that ensure strong validity, each one with a decentralized and a leader-based variant.. Our paper analyzes two Byzantine consensus algorithms that ensure strong validity, each one with a decentralized and a leader-based variant.2 One of these two algorithms is inspired by Fast Byzantine (FaB) Paxos [12], the other by PBFT [4].
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