ISO/IEC/IEEE 8802-1AS:2021/FDAmd 3

FINAL DRAFT
Amendment
ISO/IEC/IEEE
8802-1AS:2021/
FDAM 3
ISO/IEC JTC 1/SC 6
Information technology —
Secretariat: KATS
Telecommunications and
Voting begins on:
information exchange between
2026-03-13
systems — Local and metropolitan
Voting terminates on:
area networks —
2026-07-31
Part 1AS:
Second edition
Timing and synchronization for
2021-11
time-sensitive applications in
AMENDMENT 3
bridged local area networks
AMENDMENT 3: Hot standby and
clock drift error reduction
Technologies de l'information — Télécommunications et
échange d'information entre systèmes — Réseaux locaux et
métropolitains —
Partie 1AS: Temporisation et synchronisation pour les
applications sensibles au temps des réseaux locaux pontés
AMENDEMENT 3
This document is circulated as received from the committee secretariat.
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
FAST TRACK PROCEDURE
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
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TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/IEC/IEEE 8802­1AS:2021/FDAM
3:2026(en) © IEEE 2026
FINAL DRAFT
ISO/IEC/IEEE 8802-1AS:2021/FDAM 3:2026(en)
Amendment
ISO/IEC/IEEE
8802-1AS:2021/
FDAM 3
ISO/IEC JTC 1/SC 6
Information technology —
Secretariat: KATS
Telecommunications and
Voting begins on:
information exchange between
systems — Local and metropolitan
Voting terminates on:
area networks —
Part 1AS:
Second edition
Timing and synchronization for
2021-11
time-sensitive applications in
AMENDMENT 3
bridged local area networks
AMENDMENT 3: Hot standby and
clock drift error reduction
Technologies de l'information — Télécommunications et
échange d'information entre systèmes — Réseaux locaux et
métropolitains —
Partie 1AS: Temporisation et synchronisation pour les
applications sensibles au temps des réseaux locaux pontés
AMENDEMENT 3
This document is circulated as received from the committee secretariat.
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPORTING D OCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
© IEEE 2026
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
FAST TRACK PROCEDURE
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
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Reference number
Published in Switzerland ISO/IEC/IEEE 8802­1AS:2021/FDAM
3:2026(en)
© IEEE 2024
© IEEE 2026 – All rights reserved
ii
Foreword
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IEEE Std 802.1ASdm-2024) and drafted in accordance with its editorial rules. It was adopted, under the “fast-
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© IEEE 2024 – All rights reserved
iii
ISO/IEC/IEEE 8802-1AS:2021/Amd 3:2026(en)

ISO/IEC/IEEE 8802-1AS:2021/Amd 3:2026(en)
Title page
IEEE Std 802.1ASdm™-2024
(Amendment to IEEE Std 802.1AS™-2020
as amended by IEEE Std 802.1AS™-2020/Cor 1-2021,
IEEE Std 802.1ASdr™-2024,
and IEEE Std 802.1ASdn™-2024)
IEEE Standard for
Local and Metropolitan Area Networks—
Timing and Synchronization for
Time-Sensitive Applications
Amendment 3: Hot Standby and Clock
Drift Error Reduction
Developed by the
LAN/MAN Standards Committee
of the
IEEE Computer Society
Approved 26 September 2024
IEEE SA Standards Board
ISO/IEC/IEEE 8802-1AS:2021/Amd 3:2026(en)
Abstract: This amendment to IEEE Std 802.1AS™-2020 specifies hot standby and addresses
errors and omissions in the description of existing functionality.
Keywords: amendment, best timeTransmitter, frequency offset, Grandmaster Clock, Grandmaster
PTP Instance, hot standby, IEEE 802.1AS™, IEEE 802.1ASdm™, phase offset, PTP End Instance,
PTP Relay Instance, synchronization, syntonization, time-aware system
The Institute of Electrical and Electronics Engineers, Inc.
3 Park Avenue, New York, NY 10016-5997, USA
All rights reserved. Published 4 October 2024 Printed in the United States of America.
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PDF: ISBN 979-8-8557-1240-7 STD27316
Print: ISBN 979-8-8557-1241-4 STDPD27316
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ISO/IEC/IEEE 8802-1AS:2021/Amd 3:2026(en)
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ISO/IEC/IEEE 8802-1AS:2021/Amd 3:2026(en)
Participants
At the time this standard was submitted to the IEEE SA Standards Board for approval, the IEEE 802.1
Working Group had the following membership:
Glenn Parsons, Chair
Jessy V. Rouyer, Vice Chair
János Farkas, TSN Task Group Chair
Geoffrey Garner, Editor
Katsuyuki Akizuki Yoshihiro Ito Atsushi Sato
Venkat Arunarthi Michael Karl
Frank Schewe
Stephan Kehrer
Ralf Assmann
Michael Seaman
Rudy Belliardi Marcel Kiessling
Maik Seewald
Christian Boiger Gavin Lai
Ramesh Sivakolundu
Paul Bottorff Yunping (Lily) Lyu
Johannes Specht
Radhakrishna Canchi Christophe Mangin
Nemanja Stamenic
Feng Chen Scott Mansfield
Marius Stanica
Abhijit Choudhury Olaf Mater
Guenter Steindl
Anna Engelmann David McCall
Karim Traore
Donald Fedyk Martin Mittelberger
Max Turner
Norman Finn Hiroki Nakano
Balazs Varga
Craig Gunther Takumi Nomura
Ganesh Venkatesan
Stephen Haddock Donald R. Pannell
Leon Wessels
Mark Hantel Dieter Proell
Ludwig Winkel
Marc Holness Karen Randall
Jordon Woods
Daniel Hopf Maximilian Riegel
Takahiro Yamaura
Woojung Huh Silvana Rodrigues
Satoko Itaya Rajeev Roy Nader Zein
The following members of the individual balloting committee voted on this standard. Balloters may have
voted for approval, disapproval, or abstention.
Thomas Alexander Lokesh Kabra Dieter Proell
Piotr Karocki
Boon Chong Ang Denis Reilly
Stephan Kehrer
Butch Anton Maximilian Riegel
Douglas Arnold Stuart Kerry
Silvana Rodrigues
Stefan Aust Yongbum Kim
Benjamin Rolfe
Denis Beaudoin Jeff Koftinoff
Zoltan Roman
Christian Boiger Gavin Lai
Jessy V. Rouyer
Vern Brethour Hyeong Ho Lee
Reinhard Schrage
Juan Carreon Joseph Levy
Jhony Sembiring
Pin Chang Greg Luri
Johannes Specht
David Chen Jingfei Lv
Guenter Steindl
Rodney Cummings Christophe Mangin
Walter Struppler
János Farkas William-Rogelio Marchand-Niño
David Tepen
Donald Fedyk Brett McClellan
Richard Tse
Avraham Freedman Jonathon McLendon
Max Turner
Martin Mittelberger
Geoffrey Garner
Ganesh Venkatesan
Craig Gunther Ronald Murias
John Vergis
Marco Hernandez Rajesh Murthy
Xiaohui Wang
Werner Hoelzl Mfanasibili Nkonyane
Stephen Webb
Oliver Holland Satoshi Obara
Karl Weber
Tetsushi Ikegami Glenn Parsons
Scott Willy
Yoshihiro Ito Bansi Patel
Ludwig Winkel
Abdul Jabbar Arumugam Paventhan
Andreas Wolf
Raj Jain Cam Posani
SangKwon Jeong Clinton Powell Oren Yuen
Pranav Jha Venkatesha Prasad Qiyue Zou
ISO/IEC/IEEE 8802-1AS:2021/Amd 3:2026(en)
When the IEEE SA Standards Board approved this standard on 26 September 2024, it had the following
membership:
David J. Law, Chair
Jon W. Rosdahl, Vice Chair
Gary Hoffman, Past Chair
Alpesh Shah, Secretary
Sara R. Biyabani Hao Hu Hiroshi Mano
Paul Nikolich
Ted Burse Yousef Kimiagar
Robby Robson
Stephen Dukes Joseph L. Koepfinger*
Lei Wang
Doug Edwards Howard Li
F. Keith Waters
J. Travis Griffith Xiaohui Liu
Sha Wei
Guido R. Hiertz John Haiying Lu
Philip B. Winston
Ronald W. Hotchkiss Kevin W. Lu
Don Wright
*Member Emeritus
ISO/IEC/IEEE 8802-1AS:2021/Amd 3:2026(en)
Introduction
This introduction is not part of IEEE Std 802.1ASdm-2024, IEEE Standard for Local and Metropolitan Area
Networks—Timing and Synchronization for Time-Sensitive Applications—Amendment 3: Hot Standby and Clock
Drift Error Reduction.
The first edition of IEEE Std 802.1AS was published in 2011. A first corrigendum, IEEE Std
802.1AS™-2011/Cor 1-2013, provided technical and editorial corrections. A second corrigendum, IEEE Std
802.1AS™-2011/Cor 2-2015 provided additional technical and editorial corrections.
The second edition, IEEE Std 802.1AS-2020, added support for multiple gPTP domains, Common Mean
Link Delay Service, external port configuration, and Fine Timing Measurement for 802.11 transport.
Backward compatibility with IEEE Std 802.1AS-2011 was maintained. A corrigendum, IEEE Std
802.1AS-2020/Cor 1-2021, provides technical and editorial corrections.
This amendment to IEEE Std 802.1AS-2020 specifies hot standby and addresses errors and omissions in the
description of existing functionality. Hot standby guards against the failure of a single Grandmaster PTP
Instance or the failure of communication from that Grandmaster PTP Instance to a Clock Target.
ISO/IEC/IEEE 8802-1AS:2021/Amd 3:2026(en)
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