Title

Time Enough: Synchronization for Latency Measurement

Date of Award

Fall 2020

Project Type

Thesis

Program or Major

Computer Science

Degree Name

Master of Science

First Advisor

Radim Bartoš

Second Advisor

Elizabeth Varki

Third Advisor

Daniel Moss

Abstract

Latency is an essential measure of network performance, and specific latency limits are core elements of quality of service guarantees across application domains. Measuring one-way latency depends on clock synchronization, but the very network impairments revealed by changes in one-way latency can themselves degrade the accuracy of network-based clock synchronization, on which one-way latency measurement often depends. While expensive hardware-based solutions address such issues, lower-cost, software-based solutions more readily deployed would pose a significant opportunity. This thesis evaluates three network time synchronization methods' performance under the network impairments of latency asymmetry and packet jitter, with respect to the resulting accuracy of the one-way latency measurements those methods support. While all network-based methods were found to suffer equally under latency asymmetry, all producing the theoretically predicted maximum error, Linux PTP's implementation of IEEE 1588 Precise Time Protocol was found to perform exceptionally well under jitter impairments. In addition to recommending Linux PTP for clock synchronization in support of accurate one-way latency measurement under jitter conditions, a testbed design for future research and product development is also presented.

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