Motorway: Seamless high speed BFT

Today's practical, high performance Byzantine Fault Tolerant (BFT) consensus protocols operate in the partial synchrony model. However, existing protocols are often inefficient when networks are indeed partially synchronous. They obtain either low latency during synchrony or robust recovery from periods of asynchrony. At one end, traditional, view-based BFT protocols optimize for latency in the sunny-network case, but when faced with periods of asynchrony are subject to performance degradations (hangovers) that can last beyond the return to synchrony. At the other end, modern DAG-based BFT protocols recover gracefully from asynchrony, but exhibit lackluster latency during synchronous intervals. To close the gap, this work presents Motorway, a novel high-throughput BFT protocol that offers both low latency and seamless recovery from periods of asynchrony. Motorway combines a highly parallel asynchronous data dissemination layer with a low-latency, partially synchronous consensus mechanism to construct an efficient consensus protocol for partial synchrony. Motorway (i) avoids the hangovers incurred by traditional BFT protocols and (ii) matches the throughput of state of the art DAG-BFT protocols while reducing latency by 2.1x, matching the latency of traditional BFT protocols.