Clock Skew Models for ns-3

Time synchronization is an important component in understanding protocols dealing with race conditions, deadlocks, mutual exclusion, and other timing bugs that may occur in a real-world network.The asynchronous nature of today's networks makes clock skew an important issue to model, and our simulation should reflect the same to avoid those timing bugs in production environments.In this work, we motivate the need for a clock skew model in ns-3, where each node exhibits drift based on a bound configured by the user.The ns-3 documentation outlines the need for a node-local clock to model this drift, and having this model would allow users to better understand timing bugs that may occur in production.We provide several models of skewing clocks implemented in ns-3, and an abstraction of NTP to illustrate a synchronization model built on top of these skewing clocks.We also provide an analysis of the overheads and deviations from a reference observed when these models are used.In addition, we provide different clock designs used in traditional distributed systems to aid users with alternatives to skewing physical clocks.