A New and Improved Algorithm for Fault-Tolerant Clock Synchronization

Abstract

Synchronous clocks are an essential requirement for a variety of distributed system applications. Many of these applications are safety-critical and require fault tolerance. In this paper, a new "Sliding Window" clock synchronization algorithm is presented. It offers two significant advantages. First, it can tolerate considerably higher percentages of faults than any known algorithm. In addition, it achieves clock synchronization tightness that is tighter than or as tight as that of other algorithms. A comprehensive simulation environment is used for an evaluation and comparison of the Sliding Window Algorithm with other clock synchronization algorithms. A quantitative evaluation using this environment outlines the achievable tightness under different conditions and shows that the Sliding Window Algorithm is capable of tolerating more than 50% of the nodes being faulty at any time as well as short fault bursts that affect all nodes. The evaluation also shows that our algorithm synchronizes up to 38% tighter than other algorithms. Finally, it is proven that the algorithm is able to guarantee synchronization in an n-node system even if the number of Byzantine faults is n/4.