Most of the Blockchain permissioned systems employ Byzantine fault-tolerance (BFT) consensus protocols to ensure that honest validators agree on the order for appending entries to their ledgers. In this paper, we study the performance and the scalability of prominent consensus protocols, namely PBFT, Tendermint, HotStuff, and Streamlet, both analytically via load formulas and practically via implementation and evaluation. Under identical conditions, we identify the bottlenecks of these consensus protocols and show that these protocols do not scale well as the number of validators increases. Our investigation points to the communication complexity as the culprit. Even when there is enough network bandwidth, the CPU cost of serialization and deserialization of the messages limits the throughput and increases the latency of the protocols. To alleviate the bottlenecks, the most useful techniques include reducing the communication complexity, rotating the hotspot of communications, and pipelining across consensus instances.

翻译：在本文中,我们研究了主要共识协议(即PBFT、Tendermint、HotStuff和Streamlet)的性能和可扩展性,这些协议是通过负载公式进行分析,并实际通过执行和评价进行。在同样条件下,我们找出这些协商一致协议的瓶颈,并表明这些协议没有扩大规模,验证者的数量也有所增加。我们的调查指出通信的复杂性是罪魁祸首。即使网络带宽足够多,但信息序列化和淡化的CPU成本限制了协议的吞吐量并增加了时间。为缓解瓶颈,最有用的技术包括减少通信复杂性、通信热点旋转以及跨越协商一致案例。