The distributed computing literature considers multiple options for modeling communication. Most simply, communication is categorized as either synchronous or asynchronous. Synchronous communication assumes that messages get delivered within a publicly known timeframe and that parties' clocks are synchronized. Asynchronous communication, on the other hand, only assumes that messages get delivered eventually. A more nuanced approach, or a middle ground between the two extremes, is given by the partially synchronous model, which is arguably the most realistic option. This model comes in two commonly considered flavors: (i) The Global Stabilization Time (GST) model: after an (unknown) amount of time, the network becomes synchronous. This captures scenarios where network issues are transient. (ii) The Unknown Latency (UL) model: the network is, in fact, synchronous, but the message delay bound is unknown. This work formally establishes that any time-agnostic property that can be achieved by a protocol in the UL model can also be achieved by a (possibly different) protocol in the GST model. By time-agnostic, we mean properties that can depend on the order in which events happen but not on time as measured by the parties. Most properties considered in distributed computing are time-agnostic. The converse was already known, even without the time-agnostic requirement, so our result shows that the two network conditions are, under one sensible assumption, equally demanding.

翻译：分布式计算文献中考虑了多种通信建模选项。最简单的情况下，通信被分为同步或异步两类：同步通信假设消息在公开已知的时间范围内送达，且各参与方的时钟保持同步；而异步通信仅假设消息最终会被送达。介于两种极端之间的更细致化方案是部分同步模型，这可谓最现实的选项。该模型有两种常见变体：（i）全局稳定时间（GST）模型：在（未知的）时间点之后，网络变为同步，这刻画了网络问题具有瞬态性的场景；（ii）未知延迟（UL）模型：网络实际上是同步的，但消息延迟的界限未知。本文正式证明：在UL模型中协议可实现的任何时间不可知性质，也能够在GST模型中通过（可能不同的）协议实现。所谓"时间不可知"是指性质可依赖于事件发生的顺序，而非参与方所度量的时间。分布式计算中考虑的大多数性质均为时间不可知。相反方向的结论（即使不要求时间不可知）已为已知结果，因此我们的研究表明：在一种合理的假设下，这两种网络条件具有同等的约束力。