Logical clocks

Goal: Allow processes on different systems to identify causal relationships and their ordering among events, particularly among messages sent between different systems. A computer’s time-of-day clocks (known as wall clocks) rely on real-world time. They are usually set by contacting a server that has the time, often via NTP (the Network Time Protocol). These clocks have some inaccuracies due to the imperfect physical nature of the quartz crystals that make them oscillate. These inaccuracies create clock drift, leading to the likelihood that two computers will report slightly different time values if queried at the same time. To correct for drift, computers periodically re-sync their clocks via NTP. However, even NTP synchronization does not yield perfectly accurate time and the clock continues to drift between synchronizations. Because of this, we cannot definitively determine that one event occurred before another event by simply comparing the timestamps of the events. In a large envi

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