  With upcoming blockchain infrastructures, world-spanning Byzantine consensus
is getting practical and necessary. In geographically distributed systems, the
pace at which consensus is achieved is limited by the heterogenous latencies of
connections between replicas. If deployed on a wide-area network,
consensus-based systems benefit from weighted replication, an approach that
utilizes extra replicas and assigns higher voting power to well connected
replicas. This enables more choice in quorum formation and replicas can
leverage proportionally smaller quorums to advance, thus decreasing consensus
latency. However, the system needs a solution to autonomously adjust to its
environment if network conditions change or faults occur. We present Adaptive
Wide-Area REplication (AWARE), a mechanism which improves the geographical
scalability of consensus with nodes being widely spread across the world.
Essentially, AWARE is an automated and dynamic voting weight tuning and leader
positioning scheme, which supports the emergence of fast quorums in the system.
It employs a reliable self-monitoring process and provides a prediction model
seeking to minimize the system's consensus latency. In experiments using
several AWS EC2 regions, AWARE dynamically optimizes consensus latency by
self-reliantly finding a fast weight configuration yielding latency gains
observed by clients located across the globe.
