Scaling Blockchain Consensus via a Robust Shared Mempool

Leader-based Byzantine fault-tolerant (BFT) consensus protocols used by permissioned blockchains have limited scalability and robustness. To alleviate the leader bottleneck in BFT consensus, we introduce Stratus, a robust shared mempool protocol that decouples transaction distribution from consensus. Our idea is to have replicas disseminate transactions in a distributed manner and have the leader only propose transaction ids. Stratus uses a provably available broadcast (PAB) protocol to ensure the availability of the referenced transactions. To deal with unbalanced load across replicas, Stratus adopts a distributed load balancing protocol.

We implemented and evaluated Stratus by integrating it with state-of-the-art BFT-based blockchain protocols. Our evaluation of these protocols in both LAN and WAN settings shows that Stratus-based protocols achieve 5× to 20× higher throughput than their native counterparts in a network with hundreds of replicas. In addition, the performance of Stratus degrades gracefully in the presence of network asynchrony, Byzantine attackers, and unbalanced workloads.