iHorology: Lowering the Barrier to Microsecond-level Internet Time

TL;DR

iHorology introduces methods to significantly reduce clock synchronization errors caused by path asymmetry, aiming to achieve microsecond-level accuracy for Internet timekeeping.

Contribution

The paper presents three novel approaches leveraging multiple servers to tighten bounds on path asymmetry, advancing high-precision Internet time synchronization.

Findings

Substantial error reduction demonstrated through simulations.

Path asymmetry is a key barrier to microsecond accuracy.

Potential for achieving microsecond synchronization discussed.

Abstract

High precision, synchronized clocks are essential to a growing number of Internet applications. Standard protocols and their associated server infrastructure have been shown to typically enable client clocks to synchronize on the order of tens of milliseconds. We address one of the key challenges to high precision Internet timekeeping - the intrinsic contribution to clock error of path asymmetry between client and time server, a fundamental barrier to microsecond level accuracy. We first exploit results of a measurement study to quantify asymmetry and its effect on timing. We then describe three approaches to addressing the path asymmetry problem: LBBE, SBBE and K-SBBE, each based on timestamp exchange with multiple servers, with the goal of tightening bounds on asymmetry for each client. We explore their capabilities and limitations through simulation and argument. We show that substantial improvements are possible, and discuss whether, and how, the goal of microsecond accuracy might be attained.