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Improved algorithms for synchronizing computer network clocks

Author:

David L. MillsAuthors Info & Claims

ACM SIGCOMM Computer Communication Review, Volume 24, Issue 4

Pages 317 - 327

https://doi.org/10.1145/190809.190343

Published: 01 October 1994 Publication History

Abstract

The Network Time Protocol (NTP) is widely deployed in the Internet to synchronize computer clocks to each other and to international standards via telephone modem, radio and satellite. The protocols and algorithms have evolved over more than a decade to produce the present NTP Version 3 specification and implementations. Most of the estimated deployment of 100,000 NTP servers and clients enjoy synchronization to within a few tens of milliseconds in the Internet of today.

This paper describes specific improvements developed for NTP Version 3 which have resulted in increased accuracy, stability and reliability in both local-area and wide-area networks. These include engineered refinements of several algorithms used to measure time differences between a local clock and a number of peer clocks in the network, as well as to select the best ensemble from among a set of peer clocks and combine their differences to produce a clock accuracy better than any in the ensemble.

This paper also describes engineered refinements of the algorithms used to adjust the time and frequency of the local clock, which functions as a disciplined oscillator. The refinements provide automatic adjustment of message-exchange intervals in order to minimize network traffic between clients and busy servers while maintaining the best accuracy. Finally, this paper describes certain enhancements to the Unix operating system software in order to realize submillisecond accuracies with fast workstations and networks.

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Cited By

Chen PYang Z(2023)Understanding PTP Performance in Today’s Wi-Fi NetworksIEEE/ACM Transactions on Networking10.1109/TNET.2023.326774831:6(3037-3050)Online publication date: Dec-2023
https://doi.org/10.1109/TNET.2023.3267748
Broz FLehmann HNehaniv CDautenhahn K(2013)Automated Analysis of Mutual Gaze in Human Conversational PairsEye Gaze in Intelligent User Interfaces10.1007/978-1-4471-4784-8_4(41-60)Online publication date: 2013
https://doi.org/10.1007/978-1-4471-4784-8_4
Oliveira POkazaki AFrohlich A(2012)Time Synchronization at OS Level Using the IEEE 1588 ProtocolProceedings of the 2012 Brazilian Symposium on Computing System Engineering10.1109/SBESC.2012.37(153-156)Online publication date: 5-Nov-2012
https://dl.acm.org/doi/10.1109/SBESC.2012.37
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Improved algorithms for synchronizing computer network clocks

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Published In

cover image ACM SIGCOMM Computer Communication Review

ACM SIGCOMM Computer Communication Review Volume 24, Issue 4

Oct. 1994

318 pages

ISSN:0146-4833

DOI:10.1145/190809

Editor:
David Oran
Digital Equipment Corp., Littleton, MA

Issue’s Table of Contents

SIGCOMM '94: Proceedings of the conference on Communications architectures, protocols and applications
October 1994
328 pages
ISBN:0897916824
DOI:10.1145/190314
Chairman:
Jon Crowcroft
Univ. College London, UK

Copyright © 1994 ACM.

Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from [email protected]

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Association for Computing Machinery

New York, NY, United States

Publication History

Published: 01 October 1994

Published in SIGCOMM-CCR Volume 24, Issue 4

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Citations

Cited By

Chen PYang Z(2023)Understanding PTP Performance in Today’s Wi-Fi NetworksIEEE/ACM Transactions on Networking10.1109/TNET.2023.326774831:6(3037-3050)Online publication date: Dec-2023
https://doi.org/10.1109/TNET.2023.3267748
Broz FLehmann HNehaniv CDautenhahn K(2013)Automated Analysis of Mutual Gaze in Human Conversational PairsEye Gaze in Intelligent User Interfaces10.1007/978-1-4471-4784-8_4(41-60)Online publication date: 2013
https://doi.org/10.1007/978-1-4471-4784-8_4
Oliveira POkazaki AFrohlich A(2012)Time Synchronization at OS Level Using the IEEE 1588 ProtocolProceedings of the 2012 Brazilian Symposium on Computing System Engineering10.1109/SBESC.2012.37(153-156)Online publication date: 5-Nov-2012
https://dl.acm.org/doi/10.1109/SBESC.2012.37
Bettini L(2008)Timed buffersComputer Communications10.1016/j.comcom.2008.05.00131:14(3209-3222)Online publication date: 1-Sep-2008
https://dl.acm.org/doi/10.1016/j.comcom.2008.05.001
Piqueira JOliveira MMonteiro L(2006)Synchronous state in a fully connected phase-locked loop networkMathematical Problems in Engineering10.1155/MPE/2006/523562006(1-12)Online publication date: 2006
https://doi.org/10.1155/MPE/2006/52356
Yunyi JBugong XShihua WBuchun L(2006)On End-to-End Network Clock Offset Compensation Algorithm and Its Implementation2007 Chinese Control Conference10.1109/CHICC.2006.4347512(666-670)Online publication date: Jul-2006
https://doi.org/10.1109/CHICC.2006.4347512
Zhou SSun YTang B(2006)A Time Synchronization Algorithm in CSCW2006 Chinese Control Conference10.1109/CHICC.2006.280534(1001-1003)Online publication date: Aug-2006
https://doi.org/10.1109/CHICC.2006.280534
Li COfek Y(2006)Distributed source-destination synchronization using inband clock distributionIEEE Journal on Selected Areas in Communications10.1109/49.48170114:1(153-161)Online publication date: 1-Sep-2006
https://dl.acm.org/doi/10.1109/49.481701
Lee HLee GKwon Y(2005)Schemes for Indoor Network Synchronization in UWB PositioningKey Engineering Materials10.4028/www.scientific.net/KEM.277-279.233277-279(233-241)Online publication date: Jan-2005
https://doi.org/10.4028/www.scientific.net/KEM.277-279.233
Dauphin PHofmann R(2005)HASSE: a tool for analyzing causal relationships in parallel and distributed systemsQuantitative Evaluation of Computing and Communication Systems10.1007/BFb0024321(269-283)Online publication date: 9-Jun-2005
https://doi.org/10.1007/BFb0024321
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