ISO/IEC/IEEE 8802-1AS:2021

Information technology — Telecommunications and information exchange between systems — Local and metropolitan area networks — Part 1AS: Timing and synchronization for time-sensitive applications in bridged local area networks

This document specifies protocols, procedures, and managed objects used to ensure that the synchronization requirements are met for time-sensitive applications, such as audio, video, and time-sensitive control, across networks, for example, IEEE 802 and similar media. This includes the maintenance of synchronized time during normal operation and following addition, removal, or failure of network components and network reconfiguration. It specifies the use of IEEE 1588™ specifications where applicable in the context of IEEE Std 802.1Q™-2018.1 Synchronization to an externally provided timing signal [e.g., a recognized timing standard such as Coordinated Universal Time (UTC) or International Atomic Time (TAI)] is not part of this standard but is not precluded.

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

General Information

• Status: Published
• Publication Date: 09-Nov-2021
• ICS: 35.110 - Networking
• Technical Committee: ISO/IEC JTC 1/SC 6 - Telecommunications and information exchange between systems
• Drafting Committee: ISO/IEC JTC 1/SC 6 - Telecommunications and information exchange between systems
• Current Stage: 6060 - International Standard published
• Start Date: 10-Nov-2021
• Due Date: 28-Aug-2022
• Completion Date: 10-Nov-2021

Relations

• Revises: ISO/IEC/IEEE 8802-1AS:2014 - Information technology — Telecommunications and information exchange between systems — Local and metropolitan area networks — Part 1AS: Timing and synchronization for time-sensitive applications in bridged local area networks
• Effective Date: 06-Jun-2022
• Corrected By: ISO/IEC/IEEE 8802-1AS:2021/Cor 1:2023 - Information technology — Telecommunications and information exchange between systems — Local and metropolitan area networks — Part 1AS: Timing and synchronization for time-sensitive applications in bridged local area networks — Technical Corrigendum 1: Technical and editorial corrections
• Effective Date: 03-Sep-2022

Standards Content (Sample)

INTERNATIONAL IS O/IEC/
STANDARD IEEE
8802-1AS
Second edition
2021-11
Information technology —
Telecommunications and information
exchange between systems — Local
and metropolitan area networks —
Part 1AS:
Timing and synchronization for time-
sensitive applications in bridged local
area networks
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
Reference number
ISO/IEC/IEEE 8802-1AS:2021(E)
© IEEE 2020

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ISO/IEC/IEEE 8802-1AS:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© IEEE 2020
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Email: [e-mail]
Website: www.ieee.org
Published in Switzerland
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 © IEEE 2020 – All rights reserved

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ISO/IEC/IEEE 8802-1AS:2021(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical activity.
ISO and IEC technical committees collaborate in fields of mutual interest. Other international
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The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO/IEC documents should be noted (see www.iso.org/directives or
www.iec.ch/members_experts/refdocs).
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Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights. Details
of any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents) or the IEC list of patent
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see www.iso.org/iso/foreword.html. In the IEC, see www.iec.ch/understanding-standards.
ISO/IEC/IEEE 8802-1AS was prepared by the LAN/MAN of the IEEE Computer Society (as IEEE Std
802.1AS-2020) and drafted in accordance with its editorial rules. It was adopted, under the “fast-track
procedure” defined in the Partner Standards Development Organization cooperation agreement between
ISO and IEEE, by Joint Technical Committee ISO/IEC JTC 1, Information technology, Subcommittee SC 6,
Telecommunications and information exchange between systems.
A list of all parts in the ISO/IEC/IEEE 8802 series can be found on the ISO and IEC websites.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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© IEEE 2020 – All rights reserved iii

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ISO/IEC/IEEE 8802-1AS:2021(E)
Abstract: Protocols, procedures, and managed objects for the transport of timing over local are a
networks are defined in this standard. It includes the transport of synchronized time, the selection
of the timing source (i.e., best master), and the indication of the occurrence and magnitude of
timing impairments (i.e., phase and frequency discontinuities).
Keywords: best master, frequency offset, Grandmaster Clock, Grandmaster PTP Instance,
PTP End Instance, PTP Relay Instance, IEEE 802.1AS™, phase offset, synchronization,
syntonization, time-aware system
The Institute of Electrical and Electronics Engineers, Inc.
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ISO/IEC/IEEE 8802-1AS:2021(E)
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ISO/IEC/IEEE 8802-1AS:2021(E)
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ISO/IEC/IEEE 8802-1AS:2021(E)
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ISO/IEC/IEEE 8802-1AS:2021(E)
Participants
At the time this revision was submitted to the IEEE SA Standards Board for approval, the IEEE 802.1
Working Group had the following membership:
Glenn Parsons, Chair
John Messenger, Vice Chair
János Farkas, Chair, Time-Sensitive Networking Task Group
Craig Gunther, Vice Chair, Time-Sensitive Networking Task Group
Geoffrey Garner, Editor
Stephan Kehrer, MIB Editor
Astrit Ademaj Michael Karl Jessy Rouyer
Ralf Assmann Randy Kelsey
Atsushi Sato
Jens Bierschenk Hajime Koto Frank Schewe
Christian Boiger James Lawlis Michael Seaman
Christophe Mangin
Paul Bottorff Maik Seewald
Radhakrishna Canchi Scott Mansfield Johannes Specht
Feng Chen Kenichi Maruhashi Marius Stanica
Weiying Cheng David McCall Guenter Steindl
Paul Congdon Larry McMillan Karim Traore
Rodney Cummings Tero Mustala Xinyuan Wang
Josef Dorr Roy Myers Tongtong Wang
Hiroki Nakano
Hesham Elbakoury Hao Wang
Thomas Enzinger Bob Noseworthy Karl Weber
Donald Fedyk Tomoki Ohsawa Brian Weis
Hiroshi Ohue
Norman Finn Ludwig Winkel
Marina Gutierrez Donald Pannell Jordon Woods
Stephen Haddock Michael Potts Takahiro Yamaura
Mark Hantel Dieter Proell Nader Zein
Marc Holness Wei Qiu William Zhao
Satoko Itaya Karen Randall Helge Zinner
Yoshihiro Ito Maximilian Riegel Harald Zweck
The following members of the balloting committee voted on this standard. Balloters may have voted fo r
approval, disapproval, or abstention.
Robert Aiello Charles Cook Marina Gutierrez
Rodney Cummings
Thomas Alexander Stephen Haddock
Amelia Andersdotter William Dickerson Mark Hantel
Carol Ansley Michael Dood Marco Hernandez
Butch Anton János Farkas Werner Hoelzl
Stefan Aust Norman Finn Woojung Huh
Michael Fischer C. Huntley
Philip Beaumont
Gordon Bechtel John Fletcher Noriyuki Ikeuchi
Harry Bims Avraham Freedman Atsushi Ito
Christian Boiger Matthias Fritsche Raj Jain
Kenneth Bow Yukihiro Fujimoto SangKwon Jeong
Nancy Bravin Geoffrey Garner Lokesh Kabra
Vern Brethour Devon Gayle Manabu Kagami
Dietmar Bruckner Mietek Glinkowski Innocent Kamwa
Demetrio Bucaneg Zhigang Gong Piotr Karocki
Ashley Butterworth David Goodall Stephan Kehrer
William Byrd Ethan Grossman Stuart Kerry
Paul Cardinal Randall Groves Evgeny Khorov
Juan Carreon Stephen Guendert Yongbum Kim
David Chalupsky Michael Gundlach Patrick Kinney
Thomas Kurihara
David Chen Craig Gunther
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ISO/IEC/IEEE 8802-1AS:2021(E)
Chung-Yiu Lam Michael Newman Veselin Skendzic
Robert Landman Nick S. A. Nikjoo Manikantan Srinivasan
Hyeong Ho Lee Paul Nikolich Kevin Stanton
John Lemon Satoshi Obara Thomas Starai
James Lepp Robert O’Hara Walter Struppler
Daniel Levesque David Olsen David Thompson
Glenn Parsons
Jon Lewis Payam Torab
Michael Lynch Bansi Patel Mark-Rene Uchida
John Mackay Arumugam Paventhan James Van De Ligt
Bruce Mackie Walter Pienciak Dmitri Varsanofiev
Nicolai Malykh Clinton Powell George Vlantis
Vinayagam Mariappan R. K. Rannow Khurram Waheed
Roger Marks Alon Regev Lisa Ward
Arthur Marris Denis Reilly Stephen Webb
Maximilian Riegel
Jeffery Masters Karl Weber
Stephen McCann Robert Robinson Hung-Yu Wei
Brett McClellan Silvana Rodrigues Scott Willy
Sven Meier Jessy Rouyer Ludwig Winkel
Richard Mellitz Richard Roy Andreas Wolf
Michael Montemurro Peter Saunderson Yu Yuan
Matthew Mora Frank Schewe Oren Yuen
Bruce Muschlitz Michael Seaman Nader Zein
When the IEEE SA Standards Board approved this standard on 30 January 2020, it had the following
membership:
Gary Hoffman, Chair
Vacant Position, Vice Chair
Jean-Philippe Faure, Past Chair
Konstantinos Karachalios, Secretary
Ted Burse Howard Li Dorothy Stanley
J. Travis Griffith Dong Liu Mehmet Ulema
Grace Gu Kevin Lu Lei Wang
Guido R. Hiertz Paul Nikolich Sha Wei
Joseph L. Koepfinger* Damir Novosel Philip B. Winston
John D. Kulick Jon Walter Rosdahl Daidi Zhong
David J. Law Jingyi Zhou
*Member Emeritus
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ISO/IEC/IEEE 8802-1AS:2021(E)
Introduction
This introduction is not part of IEEE Std 802.1AS-2020, IEEE Standard for Local and Metropolitan Area
Networks—Timing and Synchronization for Time-Sensitive Applications.
This standard contains state-of-the-art material. The area covered by this standard is undergoing evolution.
Revisions are anticipated within the next few years to clarify existing material, to correct possible errors, and
®
to incorporate new related material. Information on the current revision state of this and other IEEE 802
standards may be obtained from
Secretary, IEEE SA Standards Board
445 Hoes Lane
Piscataway, NJ 08854 USA
8
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ISO/IEC/IEEE 8802-1AS:2021(E)
Contents
1. Overview. 17
1.1 Scope. 17
1.2 Purpose. 17
2. Normative references. 18
3. Definitions . 20
4. Acronyms and abbreviations . 23
5. Conformance. 26
5.1 Requirements terminology.26
5.2 Protocol Implementation Conformance Statement (PICS). 26
5.3 Time-aware system requirements . 26
5.4 PTP Instance requirements and options. 26
5.5 MAC-specific timing and synchronization methods for full-duplex IEEE 802.3 links . 28
5.6 MAC-specific timing and synchronization methods for IEEE Std 802.11-2016 . 29
5.7 MAC-specific timing and synchronization methods for IEEE 802.3 EPON . 29
5.8 MAC-specific timing and synchronization methods for coordinated shared 
network (CSN). 29
6. Conventions . 30
6.1 General. 30
6.2 Service specification method and notation . 30
6.3 Lexical form syntax . 30
6.4 Data types and on-the-wire formats. 30
7. Time-synchronization model for a packet network .35
7.1 General. 35
7.2 Architecture of a time-aware network . 35
7.3 Time synchronization . 42
7.4 PTP Instance architecture . 45
7.5 Differences between gPTP (IEEE Std 802.1AS) and PTP (IEEE Std 1588-2019) . 46
8. IEEE 802.1AS concepts and terminology . 48
8.1 gPTP domain. 48
8.2 Timescale . 48
8.3 Link asymmetry . 50
8.4 Messages. 51
8.5 Ports . 53
8.6 PTP Instance characterization.54
9. Application interfaces . 59
9.1 Overview of the interfaces. 59
9.2 ClockSourceTime interface . 60
9.3 ClockTargetEventCapture interface . 60
9.4 ClockTargetTriggerGenerate interface . 61
9.5 ClockTargetClockGenerator interface. 63
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ISO/IEC/IEEE 8802-1AS:2021(E)
9.6 ClockTargetPhaseDiscontinuity interface . 64
10. Media-independent layer specification. 65
10.1 Overview. 65
10.2 Time-synchronization state machines. 67
10.3 Best master clock selection, external port configuration, and announce interval setting 
state machines . 98
10.4 State machines related to signaling gPTP capability . 135
10.5 Message attributes. 142
10.6 Message formats . 143
10.7 Protocol timing characterization. 156
11. Media-dependent layer specification for full-duplex point-to-point links. 160
11.1 Overview. 160
11.2 State machines for MD entity specific to full-duplex point-to-point links.
...

FINAL
INTERNATIONAL ISO/IEC/
DRAFT
STANDARD IEEE/FDIS
8802-1AS
ISO/IEC JTC 1/SC 6
Information technology —
Secretariat: KATS
Telecommunications and information
Voting begins on:
2021-04-29 exchange between systems — Local
and metropolitan area networks —
Voting terminates on:
2021-09-16
Part 1AS:
Timing and synchronization for time-
sensitive applications in bridged local
area networks
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
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
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/IEC/IEEE FDIS 8802-1AS:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
©
NATIONAL REGULATIONS. IEEE 2020

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ISO/IEC/IEEE FDIS 8802-1AS:2021(E)

COPYRIGHT PROTECTED DOCUMENT
© IEEE 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from IEEE at the address below.
Institute of Electrical and Electronics Engineers, Inc
3 Park Avenue, New York
NY 10016-5997, USA
Email: [e-mail]
Website: www.ieee.org
Published in Switzerland
ii © IEEE 2020 – All rights reserved

---------------------- Page: 2 ----------------------
ISO/IEC/IEEE FDIS 8802-1AS:2021(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical activity.
ISO and IEC technical committees collaborate in fields of mutual interest. Other international
organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the
work.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO/IEC documents should be noted (see www.iso.org/directives or
www.iec.ch/members_experts/refdocs).
IEEE Standards documents are developed within the IEEE Societies and the Standards Coordinating
Committees of the IEEE Standards Association (IEEE-SA) Standards Board. The IEEE develops its
standards through a consensus development process, approved by the American National Standards
Institute, which brings together volunteers representing varied viewpoints and interests to achieve the
final product. Volunteers are not necessarily members of the Institute and serve without compensation.
While the IEEE administers the process and establishes rules to promote fairness in the consensus
development process, the IEEE does not independently evaluate, test, or verify the accuracy of any of the
information contained in its standards.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights. Details
of any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents) or the IEC list of patent
declarations received (see patents.iec.ch).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the World
Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT),
see www.iso.org/iso/foreword.html. In the IEC, see www.iec.ch/understanding-standards.
ISO/IEC/IEEE 8802-1AS was prepared by the LAN/MAN of the IEEE Computer Society (as IEEE Std
802.1AS-2020) and drafted in accordance with its editorial rules. It was adopted, under the “fast-track
procedure” defined in the Partner Standards Development Organization cooperation agreement between
ISO and IEEE, by Joint Technical Committee ISO/IEC JTC 1, Information technology, Subcommittee SC 6,
Telecommunications and information exchange between systems.
A list of all parts in the ISO/IEC/IEEE 8802 series can be found on the ISO and IEC websites.
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© IEEE 2020 – All rights reserved iii

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IEEE Std 802.1AS™-2020
(Revision of IEEE Std 802.1AS-2011)
IEEE Standard for 
Local and Metropolitan Area Networks—
Timing and Synchronization for
Time-Sensitive Applications
Developed by the
LAN/MAN Standards Committee 
of the 
IEEE Computer Society
Approved 30 January 2020
IEEE SA Standards Board

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ISO/IEC/IEEE FDIS 8802-1AS:2021(E)
Abstract: Protocols, procedures, and managed objects for the transport of timing over local are a
networks are defined in this standard. It includes the transport of synchronized time, the selection
of the timing source (i.e., best master), and the indication of the occurrence and magnitude of
timing impairments (i.e., phase and frequency discontinuities).
Keywords: best master, frequency offset, Grandmaster Clock, Grandmaster PTP Instance,
PTP End Instance, PTP Relay Instance, IEEE 802.1AS™, phase offset, synchronization,
syntonization, time-aware system
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ISO/IEC/IEEE FDIS 8802-1AS:2021(E)
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ISO/IEC/IEEE FDIS 8802-1AS:2021(E)
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ISO/IEC/IEEE FDIS 8802-1AS:2021(E)
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ISO/IEC/IEEE FDIS 8802-1AS:2021(E)
Participants
At the time this revision was submitted to the IEEE SA Standards Board for approval, the IEEE 802.1
Working Group had the following membership:
Glenn Parsons, Chair
John Messenger, Vice Chair
János Farkas, Chair, Time-Sensitive Networking Task Group
Craig Gunther, Vice Chair, Time-Sensitive Networking Task Group
Geoffrey Garner, Editor
Stephan Kehrer, MIB Editor
Astrit Ademaj Michael Karl Jessy Rouyer
Ralf Assmann Randy Kelsey
Atsushi Sato
Jens Bierschenk Hajime Koto Frank Schewe
Christian Boiger James Lawlis Michael Seaman
Christophe Mangin
Paul Bottorff Maik Seewald
Radhakrishna Canchi Scott Mansfield Johannes Specht
Feng Chen Kenichi Maruhashi Marius Stanica
Weiying Cheng David McCall Guenter Steindl
Paul Congdon Larry McMillan Karim Traore
Rodney Cummings Tero Mustala Xinyuan Wang
Josef Dorr Roy Myers Tongtong Wang
Hiroki Nakano
Hesham Elbakoury Hao Wang
Thomas Enzinger Bob Noseworthy Karl Weber
Donald Fedyk Tomoki Ohsawa Brian Weis
Hiroshi Ohue
Norman Finn Ludwig Winkel
Marina Gutierrez Donald Pannell Jordon Woods
Stephen Haddock Michael Potts Takahiro Yamaura
Mark Hantel Dieter Proell Nader Zein
Marc Holness Wei Qiu William Zhao
Satoko Itaya Karen Randall Helge Zinner
Yoshihiro Ito Maximilian Riegel Harald Zweck
The following members of the balloting committee voted on this standard. Balloters may have voted fo r
approval, disapproval, or abstention.
Robert Aiello Charles Cook Marina Gutierrez
Rodney Cummings
Thomas Alexander Stephen Haddock
Amelia Andersdotter William Dickerson Mark Hantel
Carol Ansley Michael Dood Marco Hernandez
Butch Anton János Farkas Werner Hoelzl
Stefan Aust Norman Finn Woojung Huh
Michael Fischer C. Huntley
Philip Beaumont
Gordon Bechtel John Fletcher Noriyuki Ikeuchi
Harry Bims Avraham Freedman Atsushi Ito
Christian Boiger Matthias Fritsche Raj Jain
Kenneth Bow Yukihiro Fujimoto SangKwon Jeong
Nancy Bravin Geoffrey Garner Lokesh Kabra
Vern Brethour Devon Gayle Manabu Kagami
Dietmar Bruckner Mietek Glinkowski Innocent Kamwa
Demetrio Bucaneg Zhigang Gong Piotr Karocki
Ashley Butterworth David Goodall Stephan Kehrer
William Byrd Ethan Grossman Stuart Kerry
Paul Cardinal Randall Groves Evgeny Khorov
Juan Carreon Stephen Guendert Yongbum Kim
David Chalupsky Michael Gundlach Patrick Kinney
Thomas Kurihara
David Chen Craig Gunther
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ISO/IEC/IEEE FDIS 8802-1AS:2021(E)
Chung-Yiu Lam Michael Newman Veselin Skendzic
Robert Landman Nick S. A. Nikjoo Manikantan Srinivasan
Hyeong Ho Lee Paul Nikolich Kevin Stanton
John Lemon Satoshi Obara Thomas Starai
James Lepp Robert O’Hara Walter Struppler
Daniel Levesque David Olsen David Thompson
Glenn Parsons
Jon Lewis Payam Torab
Michael Lynch Bansi Patel Mark-Rene Uchida
John Mackay Arumugam Paventhan James Van De Ligt
Bruce Mackie Walter Pienciak Dmitri Varsanofiev
Nicolai Malykh Clinton Powell George Vlantis
Vinayagam Mariappan R. K. Rannow Khurram Waheed
Roger Marks Alon Regev Lisa Ward
Arthur Marris Denis Reilly Stephen Webb
Maximilian Riegel
Jeffery Masters Karl Weber
Stephen McCann Robert Robinson Hung-Yu Wei
Brett McClellan Silvana Rodrigues Scott Willy
Sven Meier Jessy Rouyer Ludwig Winkel
Richard Mellitz Richard Roy Andreas Wolf
Michael Montemurro Peter Saunderson Yu Yuan
Matthew Mora Frank Schewe Oren Yuen
Bruce Muschlitz Michael Seaman Nader Zein
When the IEEE SA Standards Board approved this standard on 30 January 2020, it had the following
membership:
Gary Hoffman, Chair
Vacant Position, Vice Chair
Jean-Philippe Faure, Past Chair
Konstantinos Karachalios, Secretary
Ted Burse Howard Li Dorothy Stanley
J. Travis Griffith Dong Liu Mehmet Ulema
Grace Gu Kevin Lu Lei Wang
Guido R. Hiertz Paul Nikolich Sha Wei
Joseph L. Koepfinger* Damir Novosel Philip B. Winston
John D. Kulick Jon Walter Rosdahl Daidi Zhong
David J. Law Jingyi Zhou
*Member Emeritus
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ISO/IEC/IEEE FDIS 8802-1AS:2021(E)
Introduction
This introduction is not part of IEEE Std 802.1AS-2020, IEEE Standard for Local and Metropolitan Area
Networks—Timing and Synchronization for Time-Sensitive Applications.
This standard contains state-of-the-art material. The area covered by this standard is undergoing evolution.
Revisions are anticipated within the next few years to clarify existing material, to correct possible errors, and
®
to incorporate new related material. Information on the current revision state of this and other IEEE 802
standards may be obtained from
Secretary, IEEE SA Standards Board
445 Hoes Lane
Piscataway, NJ 08854 USA
8
Copyright © 2020 IEEE. All rights reserved.

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ISO/IEC/IEEE FDIS 8802-1AS:2021(E)
Contents
1. Overview. 17
1.1 Scope. 17
1.2 Purpose. 17
2. Normative references. 18
3. Definitions . 20
4. Acronyms and abbreviations . 23
5. Conformance. 26
5.1 Requirements terminology.26
5.2 Protocol Implementation Conformance Statement (PICS). 26
5.3 Time-aware system requirements . 26
5.4 PTP Instance requirements and options. 26
5.5 MAC-specific timing and synchronization methods for full-duplex IEEE 802.3 links . 28
5.6 MAC-specific timing and synchronization methods for IEEE Std 802.11-2016 . 29
5.7 MAC-specific timing and synchronization methods for IEEE 802.3 EPON . 29
5.8 MAC-specific timing and synchronization methods for coordinated shared 
network (CSN). 29
6. Conventions . 30
6.1 General. 30
6.2 Service specification method and notation . 30
6.3 Lexical form syntax . 30
6.4 Data types and on-the-wire formats. 30
7. Time-synchronization model for a packet network .35
7.1 General. 35
7.2 Architecture of a time-aware network . 35
7.3 Time synchronization . 42
7.4 PTP Instance architecture . 45
7.5 Differences between gPTP (IEEE Std 802.1AS) and PTP (IEEE Std 1588-2019) . 46
8. IEEE 802.1AS concepts and terminology . 48
8.1 gPTP domain. 48
8.2 Timescale . 48
8.3 Link asymmetry . 50
8.4 Messages. 51
8.5 Ports . 53
8.6 PTP Instance characterization.54
9. Application interfaces . 59
9.1 Overview of the interfaces. 59
9.2 ClockSourceTime interface . 60
9.3 ClockTargetEventCapture interface . 60
9.4 ClockTargetTriggerGenerate interface . 61
9.5 ClockTargetClockGenerator interface. 63
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ISO/IEC/IEEE FDIS 8802-1AS:2021(E)
9.6 ClockTargetPhaseDiscontinuity interface . 64
10. Media-independent layer specification. 65
10.1 Overview. 65
10.2 Time-synchronization state machines. 67
10.3 Best master clock selection, external port configuration, and announce interval setting 
state machines .
...