实用的一轮往返BFT复制
Aspen: Making Leaderless BFT Fast Paths Practical with Synchronized Clocks
AI总结：
提出Aspen协议，通过无领导推测性快速路径和尽力排序层实现接近最优的2Δ+ε延迟，并增加额外副本处理并发请求，在保持安全性的同时显著降低延迟。
摘要：
随着拜占庭容错（BFT）协议越来越多地用于面向用户的应用（如支付和智能合约），提供低延迟至关重要。为了减少延迟，一些BFT共识协议采用无领导、推测性的快速路径，客户端直接向副本广播请求，实现两个消息延迟（$2\Delta$）的端到端提交延迟。然而，这种快速路径极其脆弱：并发请求可能导致副本在接收不同顺序的请求时产生分歧，触发昂贵的恢复过程。本文提出Aspen，一种无领导推测性BFT协议，处理并发请求的同时实现接近最优的$2\Delta + \epsilon$延迟。$\epsilon$项是Aspen的尽力排序层引入的短等待延迟，该层使用松散同步的时钟和网络延迟估计来提供临时顺序。为了使其快速路径对间歇性分歧更加鲁棒，Aspen增加了额外副本（$n = 3f + 2p + 1$）以及新颖的恢复机制，允许系统在保持安全性和性能的同时容忍分歧。在跨地理分布副本的实验中，与最先进的BFT协议相比，Aspen将请求的中位延迟降低了$1.1\times$--$3.8\times$，同时保持了吞吐量优化设计峰值吞吐量的$0.75\times$。
英文摘要：
No Byzantine Fault Tolerant (BFT) protocol can commit a request in less than the single round trip it takes for clients to reach the replicas and hear back. Some protocols approach this bound with a leaderless, speculative fast path, where clients broadcast requests directly to replicas and commit in two message delays ($2Δ$). However, such a fast path is extremely fragile: when clients submit requests concurrently, replicas receive them in different orders and end up in different states, forcing the protocol into costly recovery. This paper presents Aspen, a leaderless speculative BFT protocol that can maintain its fast path even while clients submit requests concurrently, at a near-optimal latency of $2Δ+ ε$. The $ε$ term is a short waiting delay that Aspen adds to give requests a best-effort, tentative initial order using loosely synchronized clocks and network delay estimates. Since real networks are not perfectly predictable, Aspen also tolerates replicas diverging: it adds extra replicas ($n = 3f + 2p + 1$) so that the fast path survives up to $p$ diverged replicas, a lightweight alignment subprotocol that returns those replicas to the fast path in the background, and a repair subprotocol that restores agreement when too many diverge. In experiments with geo-distributed replicas, Aspen reduces the latency of requests by $1.1\times$--$5.5\times$ compared to state-of-the-art BFT protocols, while maintaining throughput matching or exceeding throughput-optimized designs.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
