Dynamically available total-order broadcast (TOB) protocols are essential in permissionless systems in which participants may unpredictably go offline and later come back online. Existing dynamically-available protocols are synchronous protocols, and they lose their safety guarantees during periods of asynchrony. This is a major issue in practice. In this paper, we explore the challenge of tolerating bounded periods of asynchrony in dynamically-available TOB protocols that ensure safety deterministically. We propose to trade off assumptions limiting the online/offline churn rate in exchange for tolerating bounded asynchronous periods through the use of a configurable message-expiration period. We show how to apply this idea to a state-of-the-art protocol to make it tolerate bounded periods of asynchrony.

翻译：动态可用全序广播（TOB）协议对于无需许可系统至关重要，其中参与者可能不可预测地离线并在稍后重新上线。现有动态可用协议均为同步协议，在异步期间会丧失其安全性保证，这在实践中是一个重大挑战。本文探讨了在确定性地保障安全性的动态可用TOB协议中容忍有限异步周期的难题。我们提出通过权衡限制在线/离线波动率的假设，并采用可配置的消息过期周期来换取对有限异步周期的容忍能力。我们展示了如何将该思想应用于最先进的协议，使其能够容忍有限异步周期。