A Fast and Robust Optimistic Total Order Broadcast for Online Video Games

Total order broadcast is a fundamental building block for many distributed systems. In recent online video games, players actions within a particular game instance need to follow a total order in order to ensure game consistency. The main challenge is to preserve game playable by keeping latency as low as possible. Relying on a single central server incurs high cost for the game editor and is vulnerable to denial of service attacks. For these reasons, a decentralized architecture is desirable. We present a total order broadcast protocol that is both fast and robust with no single point of failure. In its optimistic setting, it delivers message in just one step, which is optimal, and in two steps in its pessimistic setting. Our protocol can tolerate up to n/2-1 crashes where n is the number of processes in the system. When failures do occur, the latency is at worst linear in the number of consecutive crashes.