The concept of distributed consensus gained widespread attention following the publication of "Byzantine Generals Problem" by Leslie Lamport in the 1980s. This research topic has been active and extensively studied over the last four decades, particularly since the advent of blockchain technology in 2009. Blockchain technology employs Proof-of-X (PoX) or Byzantine-fault-tolerant (BFT) systems, where all participants follow a protocol to achieve a common state (i.e., consistency) eventually. However, because PoX consensus such as Proof-of-Work is is resource-intensive with high power consumption, most permissioned blockchains employ BFT to achieve consistency. In this article, we provide an introduction to the fundamental principles and history of distributed consensus. We then explore the well-known fault-tolerant state machine replication (SMR) in partially synchronous networks, as well as consensus protocols in asynchronous models and recently proposed DAG-based consensus. Additionally, we examine the relationship between BFT consensus and blockchain technology and discuss the following questions: What is the history and evolution of BFT? Why are BFT protocols designed in the way they are and what core components do they use? What is the connection between BFT and blockchain technology, and what are the driving needs for future BFT research?

翻译：分布式共识的概念自20世纪80年代Leslie Lamport发表《拜占庭将军问题》后受到广泛关注。在过去的四十年中，该研究主题一直保持活跃并被广泛研究，特别是在2009年区块链技术出现之后。区块链技术采用工作量证明类（Proof-of-X, PoX）或拜占庭容错（Byzantine-fault-tolerant, BFT）系统，其中所有参与者遵循协议最终达成共同状态（即一致性）。然而，由于工作量证明等PoX共识机制资源消耗大、能耗高，大多数许可型区块链采用BFT来实现一致性。本文介绍了分布式共识的基本原理与发展历程，探讨了部分同步网络中著名的容错状态机复制（SMR）技术、异步模型下的共识协议以及近期提出的基于有向无环图（DAG）的共识机制。此外，我们分析了BFT共识与区块链技术之间的关系，并讨论了以下问题：BFT的历史与演进脉络是什么？BFT协议为何采用现有设计方式，其核心组件有哪些？BFT与区块链技术有何联系，未来BFT研究的核心需求是什么？