ISO/IEC/IEEE 8802-1AS:2021/Amd 1:2025

International
Standard
ISO/IEC/IEEE
8802-1AS
Second edition
Information technology —
2021-11
Telecommunications and
information exchange between
AMENDMENT 1
systems — Local and metropolitan
2025-04
area networks —
Part 1AS:
Timing and synchronization for
time-sensitive applications in
bridged local area networks
AMENDMENT 1: Inclusive terminology
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 1: Terminologie inclusive
Reference number
ISO/IEC/IEEE 8802-1AS:2021/
Amd.1:2025(en)
© IEEE 2024
ISO/IEC/IEEE 8802-1AS:2021/Amd.1:2025(en)
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ii
ISO/IEC/IEEE 8802-1AS:2021/Amd.1:2025(en)
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iii
Title page
IEEE Std 802.1ASdr™-2024
(Amendment to IEEE Std 802.1AS™-2020
as amended by IEEE Std 802.1AS™-2020/Cor 1-2021)
IEEE Standard for
Local and Metropolitan Area Networks—
Timing and Synchronization for
Time-Sensitive Applications
Amendment 1: Inclusive Terminology
Developed by the
LAN/MAN Standards Committee
of the
IEEE Computer Society
Approved 15 February 2024
IEEE SA Standards Board
ISO/IEC/IEEE 8802-1AS:2021/Amd.1:2025(en)
Abstract: This amendment to IEEE Std 802.1AS™-2020 replaces terminology with alternative
terminology identified by IEEE Std 1588g™-2022. All changes made in figures are only to replace
terminology.
Keywords: amendment, best timeTransmitter, frequency offset, Grandmaster Clock, Grandmaster
PTP Instance, IEEE 802.1AS™, IEEE 802.1ASdr™, phase offset, PTP End Instance, PTP Relay
Instance, synchronization, syntonization, time-aware system
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ISO/IEC/IEEE 8802-1AS:2021/Amd.1:2025(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 IEEE Std 802.1AS
Silvana Rodrigues, Editor P802.1ASdr
Katsuyuki Akizuki Mark Hantel Karen Randall
Konstantinos Alexandris Marc Holness
Maximilian Riegel
Venkat Arunarthi Daniel Hopf
Atsushi Sato
Ralf Assmann Woojung Huh
Frank Schewe
Huajie Bao Satoko Itaya
Michael Seaman
Yoshihiro Ito
Rudy Belliardi
Maik Seewald
Jeremias Blendin Michael Karl
Ramesh Sivakolundu
Christian Boiger Stephan Kehrer
Johannes Specht
Paul Bottorff Marcel Kiessling
Nemanja Stamenic
Radhakrishna Canchi Gavin Lai
Marius Stanica
Feng Chen Yizhou Li
Guenter Steindl
Abhijit Choudhury Joao Lopes
Karim Traore
Paul Congdon Lily Lyu
Max Turner
Rodney Cummings Christophe Mangin
Balazs Varga
Josef Dorr Scott Mansfield
Ganesh Venkatesan
Hesham Elbakoury Olaf Mater
Tongtong Wang
Anna Engelmann David McCall
Karl Weber
Thomas Enzinger Larry McMillan
Leon Wessels
Donald Fedyk Martin Mittelberger
Ludwig Winkel
Norman Finn Hiroki Nakano
Jordon Woods
Craig Gunther Takumi Nomura
Takahiro Yamaura
Marina Gutierrez Donald R. Pannell
Stephen Haddock Dieter Proell Nader Zein
ISO/IEC/IEEE 8802-1AS:2021/Amd.1:2025(en)
The following members of the individual balloting committee voted on this standard. Balloters may have
voted for approval, disapproval, or abstention.
Thomas Alexander Raj Jain Venkatesha Prasad
Boon Chong Ang Pranav Jha Dieter Proell
Butch Anton Lokesh Kabra Alon Regev
Greg Armstrong Piotr Karocki Annette Reilly
Stefan Aust Stephan Kehrer Denis Reilly
Stuart Kerry Maximilian Riegel
Denis Beaudoin
Christian Boiger Yongbum Kim Markus Rindchen
Vern Brethour Mallory Knodel Silvana Rodrigues
Ashley Butterworth Jeff Koftinoff Benjamin Rolfe
Paul Cardinal Gavin Lai Jessy V. Rouyer
Pin Chang Hyeong Ho Lee Mark Sturza
Baw Chng Greg Luri Caroline Treuthardt
Paul Congdon Jingfei Lv Richard Tse
Rodney Cummings Christophe Mangin Max Turner
Patrick Diamond Scott Mansfield Dmitri Varsanofiev
Donald Dunn Sven Meier Ganesh Venkatesan
David Michel John Vergis
Darwin Engwer
Donald Fedyk Ronald Murias James Weaver
Andrew Fieldsend William Rogelio Marchand Nino Stephen Webb
Geoffrey Garner Mfanasibili Nkonyane Scott Willy
Marek Hajduczenia Satoshi Obara Ludwig Winkel
Marco Hernandez Bansi Patel Andreas Wolf
Werner Hoelzl Arumugam Paventhan Oren Yuen
C. Huntley Cam Posani Janusz Zalewski
When the IEEE SA Standards Board approved this standard on 15 February 2024, it had the following
membership:
David J. Law, Chair
Vacant Position, Vice Chair
Gary Hoffman, Past Chair
Alpesh Shah, Secretary
Sara R. Biyabani Yousef Kimiagar Robby Robson
Ted Burse Joseph L. Koepfinger* Jon W. Rosdahl
Stephen Dukes Howard Li Mark Siira
Doug Edwards Xiaohui Liu Lei Wang
J. Travis Griffith John Haiying Lu F. Keith Waters
Guido R. Hiertz Kevin W. Lu Sha Wei
Ronald W. Hotchkiss Hiroshi Mano Philip B. Winston
Hao Hu Paul Nikolich Don Wright
*Member Emeritus
ISO/IEC/IEEE 8802-1AS:2021/Amd.1:2025(en)
Introduction
This introduction is not part of IEEE Std 802.1ASdr-2024, IEEE Standard for Local and Metropolitan Area
Networks—Timing and Synchronization for Time-Sensitive Applications—Amendment 1: Inclusive Terminology.
The first edition of IEEE Std 802.1AS was published in 2011. A first corrigendum, IEEE Std
802.1AS-2011/Cor1-2013, provided technical and editorial corrections. A second corrigendum, IEEE St d
802.1AS-2011/Cor2-2015 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 IEEE 802.11 transport.
Backward compatibility with IEEE Std 802.1AS-2011 was maintained. A corrigendum, IEEE Std
802.1AS-2020/Cor1-2021, provides technical and editorial corrections.
This amendment to IEEE Std 802.1AS-2020 replaces terminology with alternative terminology identified by
IEEE Std 1588g-2022, IEEE Standard for a Precision Clock Synchronization Protocol for Networked
Measurement and Control Systems—Amendment 2: Master-Slave Optional Alternative Terminology. All
changes made in figures are only to replace terminology.
ISO/IEC/IEEE 8802-1AS:2021/Amd.1:2025(en)
Contents
4. Acronyms and abbreviations . 16
5. Conformance. 17
5.4 PTP Instance requirements and options. 17
5.6 MAC-specific timing and synchronization methods for IEEE Std 802.11-2016 . 18
7. Time-synchronization model for a packet network .19
7.2 Architecture of a time-aware network . 19
7.3 Time synchronization . 20
7.4 PTP Instance architecture . 21
7.5 Differences between gPTP (IEEE Std 802.1AS) and PTP (IEEE Std 1588-2019) . 22
8. IEEE 802.1AS concepts and terminology . 23
8.4 Messages. 23
8.5 Ports . 23
8.6 PTP Instance characterization.23
9. Application interfaces . 26
9.1 Overview of the interfaces. 26
9.2 ClockSourceTime interface . 26
9.3 ClockTargetEventCapture interface . 26
9.4 ClockTargetTriggerGenerate interface . 27
9.5 ClockTargetClockGenerator interface. 29
9.6 ClockTargetPhaseDiscontinuity interface . 30
10. Media-independent layer specification. 31
10.1 Overview. 31
10.2 Time-synchronization state machines. 33
10.3 Best mastertimeTransmitter clock selection, external port configuration, and announce
interval setting state machines . 54
10.5 Message attributes. 82
10.6 Message formats . 82
10.7 Protocol timing characterization.84
11. Media-dependent layer specification for full-duplex point-to-point links. 86
11.1 Overview. 86
11.2 State machines for MD entity specific to full-duplex point-to-point links. 87
11.3 Message attributes. 88
11.4 Message formats . 88
12. Media-dependent layer specification for IEEE 802.11 links. 90
12.1 Overview. 90
12.4 Determination of asCapable. 95
12.5 State machines . 95
12.6 FTM parameters. 106
12.7 Format of VendorSpecific information element. 107
12.8 Synchronization message interval . 108
ISO/IEC/IEEE 8802-1AS:2021/Amd.1:2025(en)
13. Media-dependent layer specification for interface to IEEE 802.3 Ethernet passive optical
network link . 109
13.1 Overview. 109
13.3 Message format. 113
13.5 Layering for IEEE 802.3 EPON links . 114
13.6 Service interface definitions . 114
13.7 MD entity global variables .115
13.8 State machines . 115
14. Timing and synchronization management. 117
14.1 General. 117
14.2 Default Parameter Data Set (defaultDS). 118
14.3 Current Parameter Data Set (currentDS) . 119
14.4 Parent Parameter Data Set (parentDS). 121
14.7 Acceptable MasterTimeTransmitter Table Parameter Data Set
(acceptableMasterTimeTransmitterTableDS) . 121
14.8 Port Parameter Data Set (portDS). 122
14.10 Port Parameter Statistics Data Set (portStatisticsDS). 123
14.11 Acceptable MasterTimeTransmitter Port Parameter Data Set
(acceptableMasterTimeTransmitterPortDS). 123
14.16 Common Mean Link Delay Service Link Port Parameter Data Set (cmldsLinkPortDS). 124
15. Managed object definitions. 125
15.2 Structure of the MIB . 125
15.3 Relationship to MIB in IEEE Std 802.1AS-2011 . 132
15.4 Security considerations . 133
15.5 Textual conventions defined in this MIB . 133
15.6 IEEE 802.1AS MIB module, . 134
16. Media-dependent layer specification for CSN. 205
16.1 Overview. 205
16.5 Synchronization messages . 205
16.6 Specific CSN requirements. 205
Annex A (normative) Protocol Implementation Conformance Statement (PICS) proforma . 206
A.5 Major capabilities . 206
A.7 Minimal time-aware system. 207
A.9 Best mastertimeTransmitter clock . 209
A.10 Grandmaster-capable PTP Instance . 211
A.11 Media-independent mastertimeTransmitter. 212
A.13 Media-dependent, full-duplex point-to-point link . 213
A.14 Media-dependent IEEE 802.11 link. 216
A.15 Media-dependent IEEE 802.3 EPON link . 217
A.16 Media-dependent CSN link . 217
Annex F (informative) PTP profile included in this standard .218
F.4 PTP options. 218
Annex G (informative) The asymmetry compensation measurement procedure based on line-swapping . 219
G.2 Pre-conditions for measurement . 219
ISO/IEC/IEEE 8802-1AS:2021/Amd.1:2025(en)
G.3 Measurement procedure. 219
ISO/IEC/IEEE 8802-1AS:2021/Amd.1:2025(en)
List of figures
Figure 7-8—PTP Instance model . 21
Figure 9-1—Application interfaces . 26
Figure 10-1—Model for media-independent layer of PTP Instance . 32
Figure 10-2—Time-synchronization state machines—overview and interrelationships. 34
Figure 10-3—SiteSyncSync state machine. 44
Figure 10-5—ClockMasterSyncSendClockTimeTransmitterSyncSend state machine . 47
Figure 10-6—ClockMasterSyncOffsetClockTimeTransmitterSyncOffset state machine. 49
Figure 10-7—ClockMasterSyncReceiveClockTimeTransmitterSyncReceive state machine. 51
Figure 10-8—PortSyncSyncSend state machine . 52
Figure 10-9—ClockSlaveClockTimeReceiverSync state machine . 54
Figure 10-10—Example mastertimeTransmitter/slavetimeReceiver hierarchy of PTP Instances . 56
Figure 10-11—Best mastertimeTransmitter clock selection state machines—overview
and interrelationships. 63
Figure 10-12—External port configuration state machines—overview and interrelationships . 65
Figure 10-14—PortAnnounceInformation state machine. 75
Figure 10-18—PortAnnounceTransmit state machine . 81
Figure 11-2—Transport of time-synchronization information. 86
Figure 11-3—Model for a PTP Instance of a time-aware system with full-duplex point-to-point links . 87
Figure 12-1—Timing measurement procedure for IEEE 802.11 links . 91
Figure 12-2—Fine Timing Measurement procedure for IEEE 802.11 links. 91
Figure 12-4—Media-dependent and lower entities in stations with IEEE 802.11 links . 94
Figure 12-5—MasterTimeTransmitter state machine A
(a) For TM, receives information from the PortSync entity and sends to
slavetimeReceiver, and 
(b) for FTM, receives and stores information from the PortSync entity . 97
Figure 12-6—MasterTimeTransmitter state machine B 
(a) For TM, not invoked and
(b) for FTM, receives initial FTM request from slavetimeReceiver and sends
information received from upstream to slavetimeReceiver in successive FTM frames. 98
Figure 12-7—SlaveTimeReceiver state machine . 103
Figure 13-1—IEEE 802.3 EPON time-synchronization interfaces . 112
Figure 13-2—IEEE 802.3 EPON interface model. 114
Figure G-1—Asymmetry compensation measurement procedure . 219
ISO/IEC/IEEE 8802-1AS:2021/Amd.1:2025(en)
List of tables
Table 10-1—Summary of scope of global variables used by time synchronization state machines
(see 10.2.4 and 10.2.5). 40
Table 10-2—PTP Port state definitions . 55
Table 10-3—Summary of scope of global variables used by best mastertimeTransmitter clock
selection, external port configuration, and announce interval setting state machines
(see 10.3.9 and 10.3.10). 66
Table 10-9—Values of flag bits. 83
Table 12-2—FTM parameters relevant to time-synchronization transport . 107
Table 14-2—currentDS table. 120
Table 14-6—acceptableMasterTimeTransmitterTableDS table. 122
Table 14-7—portState enumeration. 122
Table 14-13—acceptableMasterTimeTransmitterPortDS table . 124
Table 15-1—IEEE8021-AS-V2V3 MIB structure and object cross reference. 126
ISO/IEC/IEEE 8802-1AS:2021/Amd.1:2025(en)
IEEE Standard for 
Local and Metropolitan Area Networks—
Timing and Synchronization for
Time-Sensitive Applications
Amendment 1: Inclusive Terminology
(This amendment is based on IEEE Std 802.1AS™-2020 as amended by IEEE Std 802.1AS™-2020/Cor 1-2021.)
NOTE—The editing instructions contained in this amendment define how to merge the material contained therein into
the existing base standard and its amendments to form the comprehensive standard.
The editing instructions are shown in bold italic. Four editing instructions are used: change, delete, insert, and replace.
Change is used to make corrections in existing text or tables. The editing instruction specifies the location of the change
and describes what is being changed by using strikethrough (to remove old material) and underscore (to add ne w
material). Delete removes existing material. Insert adds new material without disturbing the existing material. Deletions
and insertions may require renumbering. If so, renumbering instructions are given in the editing instruction. Replace is
used to make changes in figures or equations by removing the existing figure or equation and replacing it with a ne w
one. Editing instructions, change markings, and this NOTE will not be carried over into future editions because the
changes will be incorporated into the base standard.
Notes in text, tables, and figures are given for information only and do not contain requirements needed to implement the standard.
ISO/IEC/IEEE 8802-1AS:2021/Amd.1:2025(en)
IEEE Std 802.1ASdr-2024
IEEE Standard for Local and Metropolitan Area Networks—Timing and Synchronization for Time-Sensitive Applications—
Amendment 1: Inclusive Terminology
4. Acronyms and abbreviations
Change the entries for “BMC” and “BMCA” in Clause 4 as follows:
BMCBTC best mastertimeTransmitter clock
BMCABTCA best mastertimeTransmitter clock algorithm
ISO/IEC/IEEE 8802-1AS:2021/Amd.1:2025(en)
IEEE Std 802.1ASdr-2024
IEEE Standard for Local and Metropolitan Area Networks—Timing and Synchronization for Time-Sensitive Applications—
Amendment 1: Inclusive Terminology
5. Conformance
5.4 PTP Instance requirements and options
5.4.1 Summary of requirements
Change items e) and f) in the lettered list in 5.1.4 (as amended by IEEE Std 802.1AS-2020/Cor 1-2021) as
follows:
e) Implement the ClockSlaveTimeReceiverSync state machine (10.2.13).
f) Support the following best mastertimeTransmitter clock algorithm (BMCABTCA) requirements:
1) Implement the BMCABTCA (10.3.1.1, 10.3.1.2, 10.3.2, 10.3.3, 10.3.4, 10.3.5, 10.3.6, 10.3.8,
and 10.3.10).
2) For domain 0, implement specifications for externalPortConfigurationEnabled value of FALSE
(10.3.1).
3)
...