TierFlow: A Pipelined Layered BFT Consensus Protocol for Large-Scale Blockchain

As the coverage of permissioned blockchains expands and the number of participating replicas increases, a scalable and efficient Byzantine Fault Tolerant (BFT) protocol is essential for large-scale blockchain. Unfortunately, previous BFT consensus protocols rely on a single leader to drive the protocol, which becomes a bottleneck for system scalability when the number of replicas exceeds a certain threshold. Although some proposals suggest hierarchically grouping nodes into different layers to alleviate verification pressure on the single leader. However, existing solutions only support serial execution between layers, causing performance and latency bottlenecks. To address these issues, we propose TierFlow, the first layered consensus protocol that supports pipelined execution, maintaining high throughput in scenarios with a large-scale deployment of replicas. TierFlow innovatively addresses the serial execution bottleneck in layered consensus by decoupling inter-layer consensus. To eliminate redundant phases, we use a pre-proof method to advance the next round of verification, and utilize delayed verification to merge similar verification workflows. We implement TierFlow and compare it with advanced BFT protocols such as HotStuff and Fast-HotStuff. We conduct extensive experiments with over 100 replicas, demonstrating that TierFlow achieves throughput 14x higher than Fast-HotStuff in large-scale application scenarios, with the performance disparity widening as scale increases.