Existing chain-based rotating leader BFT SMR protocols for the partially synchronous network model that commit blocks with $O(1)$ minimum latency have block periods of at least $2\delta$ (where $\delta$ is the message transmission latency). While a protocol with a block period of $\delta$ exists under the synchronous model, its minimum commit latency is linear in the size of the system. To close this gap, we present the first chain-based BFT SMR protocols with best-case delays of $\delta$ between the proposals of distinct honest leaders, and minimum commit latencies of $3\delta$. We present three protocols for the partially synchronous network model under different notions of optimistic responsiveness, two of which implement pipelining and one of which does not. All of our protocols achieve reorg resilience and two have short view lengths; properties that many existing chain-based BFT SMR protocols lack. We experimentally evaluate our protocols and show that they achieve significant increases in throughput and reductions in latency compared to the state-of-the-art, Jolteon. Our results also demonstrate that techniques commonly employed to reduce communication complexity$\unicode{x2014}$such as vote-pipelining and the use of designated vote-aggregators$\unicode{x2014}$actually reduce practical performance in many settings.

翻译：现有针对部分同步网络模型、以$O(1)$最小延迟提交区块的基于链的轮换领导者BFT SMR协议，其区块周期至少为$2\delta$（其中$\delta$为消息传输延迟）。尽管在同步模型下存在区块周期为$\delta$的协议，但其最小提交延迟与系统规模呈线性关系。为弥合这一差距，我们提出了首个基于链的BFT SMR协议系列，在诚实领导者交替提案的场景下，其最优延迟为$\delta$，最小提交延迟为$3\delta$。我们针对部分同步网络模型，在不同乐观响应性概念下设计了三个协议，其中两个实现流水线机制，一个未采用。所有协议均具备重组鲁棒性，且两个协议具备短视图长度——这是许多现有基于链的BFT SMR协议所缺乏的特性。通过实验评估，与现有最优协议Jolteon相比，我们的协议实现了显著吞吐量提升和延迟降低。实验还表明，投票流水线及指定投票聚合器等常用于降低通信复杂度的技术，在实际多场景中反而降低了性能。