On estimating clock skew for one-way measurements

Owning to the asymmetry of Internet paths, more and more studies have turned to the measurement of one-way metrics. Since the clocks at end systems often behave diversely, the synchronization between end hosts is what we care about all along. In this paper, we firstly propose a general model for clock skew estimation in one-way measurements, which turns the problem of clock skew estimation to the solution of ndimension equation group, and give the equation group needed based on different presumptions. We then present Piece-wise Reliable Clock Skew Estimation Algorithm (PRCSEA), which introduces reliability test to estimation results and eliminates the extra presumptions needed by other algorithms, such as only one clock adjustment in the measurements. PRCSEA solves the skew estimation problem in a heuristic way, and it can handle many special cases affecting the estimation of clock skew, such as routing change, clock hiccup and network congestion. PRCSEA is the only algorithm that can handle clock drift to the best of our knowledge. q 2005 Elsevier B.V. All rights reserved.