1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T G.8275.1/Y.1369.1 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 2 (03/2018) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Packet over Transport aspects Synchronization, quality and avail
2、ability targets SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS, NEXT-GENERATION NETWORKS, INTERNET OF THINGS AND SMART CITIES Internet protocol aspects Transport Precision time protocol telecom profile for phase/time synchronization with full timing support from the network A
3、mendment 2 Recommendation ITU-T G.8275.1/Y.1369.1 (2016) Amendment 2 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS G.2
4、00G.299 INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES G.300G.399 GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES G.400G.449 COORDINATION OF RADIOTELEPHONY AND LINE T
5、ELEPHONY G.450G.499 TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED ASPECTS G.1000G.1999 TRA
6、NSMISSION MEDIA CHARACTERISTICS G.6000G.6999 DATA OVER TRANSPORT GENERIC ASPECTS G.7000G.7999 PACKET OVER TRANSPORT ASPECTS G.8000G.8999 Ethernet over Transport aspects G.8000G.8099 MPLS over Transport aspects G.8100G.8199 Synchronization, quality and availability targets G.8200G.8299 Service Manage
7、ment G.8600G.8699 ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.8275.1/Y.1369.1 (2016)/Amd.2 (03/2018) i Recommendation ITU-T G.8275.1/Y.1369.1 Precision time protocol telecom profile for phase/time synchronization with full timing
8、support from the network Amendment 2 Summary Recommendation ITU-T G.8275.1/Y.1369.1 contains the ITU-T precision time protocol (PTP) profile for phase and time distribution with full timing support from the network. It provides the necessary details to utilize IEEE 1588 in a manner consistent with t
9、he architecture described in Recommendation ITU-T G.8275/Y.1369. Amendment 2 provides the following updates: - Changes Annex C to reference Annex B of ITU-T G.8275 - Corrects some settings in Tables V.2 and V.3 - Clarifies the requirements on the T-TSC when it is embedded in the end application - Ad
10、ds an example to Appendix XII. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T G.8275.1/Y.1369.1 2014-07-22 15 11.1002/1000/12197 1.1 ITU-T G.8275.1/Y.1369.1 (2014) Cor. 1 2015-01-13 15 11.1002/1000/12397 2.0 ITU-T G.8275.1/Y.1369.1 2016-06-22 15 11.1002/1000/12815 2.1 ITU-T
11、 G.8275.1/Y.1369.1 (2016) Amd. 1 2017-08-29 15 11.1002/1000/13329 2.2 ITU-T G.8275.1/Y.1369.1 (2016) Amd. 2 2018-03-16 15 11.1002/1000/13553 Keywords Full timing support, IEEE 1588, phase and time synchronization, PTP, telecom profile. * To access the Recommendation, type the URL http:/handle.itu.in
12、t/ in the address field of your web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T G.8275.1/Y.1369.1 (2016)/Amd.2 (03/2018) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in
13、 the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to st
14、andardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is
15、 covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to
16、indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is ac
17、hieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTU
18、AL PROPERTY RIGHTSITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether
19、asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautio
20、ned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2018 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of IT
21、U. Rec. ITU-T G.8275.1/Y.1369.1 (2016)/Amd.2 (03/2018) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 2 3.1 Terms defined elsewhere 2 3.2 Terms defined in this Recommendation . 2 4 Abbreviations and acronyms 2 5 Conventions 3 6 Use of PTP for phase/time distribution 3 6.1 High
22、-level design requirements 4 6.2 PTP modes and options 4 6.3 Protection aspects and Alternate BMCA 8 6.4 Phase/time traceability information 14 7 ITU-T PTP profile for phase/time distribution with full timing support from the network . 16 8 Security aspects 17 Annex A ITU-T PTP profile for phase/tim
23、e distribution with full timing support from the network . 18 A.1 Profile identification . 18 A.2 PTP attribute values 18 A.3 PTP options 23 A.4 Best master clock algorithm options 24 A.5 Path delay measurement option (delay request/delay response) 24 A.6 Clock identity format 24 A.7 Configuration m
24、anagement options . 24 A.8 Security aspects 24 A.9 Other optional features of IEEE 1588 24 A.10 PTP common header flags 24 Annex B Options to establish the PTP topology with the Alternate BMCA 26 Annex C Inclusion of an external phase/time input interface in a T-BC 27 Annex D Path trace (optional) 2
25、8 Annex E Synchronization uncertain indication (optional) 29 Annex F Use of stepsRemoved to limit reference chain (optional) 30 Annex G Monitoring a PTP MASTER port by a PTP PASSIVE port (optional) 31 Appendix I Considerations on the use of transparent clock 32 Appendix II Considerations on the tran
26、smission of Delay_Req messages . 33 Appendix III Considerations on the choice of the PTP Ethernet multicast destination address 35 iv Rec. ITU-T G.8275.1/Y.1369.1 (2016)/Amd.2 (03/2018) Page Appendix IV Considerations on the use of priority2 36 Appendix V Description of PTP clock states and associat
27、ed contents of Announce messages . 37 V.1 Purpose of this appendix 37 V.2 Description of the states . 37 V.3 Example of mapping between PTP port states and PTP clock states for a 3-port T-BC 39 V.4 T-GM Announce message contents based on the internal PTP clock states 40 V.5 T-BC Announce message con
28、tents based on the internal PTP clock states . 41 Appendix VI Operations over link aggregation 50 Appendix VII Relationship between clockClass and holdover specification . 51 Appendix VIII Considerations on a T-TSC connected to an end application 53 Appendix IX Calculation of offsetScaledLogVariance
29、 for T-GM timed by PRTC or ePRTC. 54 IX.1 Observation interval and TDEV noise generation 54 IX.2 Computation of PTP variance from TDEV 54 IX.3 Computation of offsetScaledLogVariance from PTP variance 55 Appendix X Description of a T-BC extended clockClass application 57 X.1 Purpose of T-BC extended
30、clockClass application 57 X.2 DefaultDS data set member specifications under this extended application 57 Appendix XI Considerations on native access equipment 59 Appendix XII Monitoring alternate master time information provided by a peer PTP port 60 Bibliography. 61 Rec. ITU-T G.8275.1/Y.1369.1 (2
31、016)/Amd.2 (03/2018) 1 Recommendation ITU-T G.8275.1/Y.1369.1 Precision time protocol telecom profile for phase/time synchronization with full timing support from the network Amendment 2 Editorial note: This is a complete-text publication. Modifications introduced by this amendment are shown in revi
32、sion marks relative to Recommendation ITU-T G.8275.1/Y.1369.1 (2016) plus its Amendment 1 (2017). 1 Scope This Recommendation specifies a profile for telecommunication applications based on IEEE 1588 precision time protocol (PTP). The profile specifies the IEEE 1588 functions that are necessary to e
33、nsure network element interoperability for the delivery of accurate phase/time synchronization. The profile is based on the full timing support from the network architecture as described in ITU-T G.8275 and definitions described in ITU-T G.8260. This version of the profile specifies the high-level d
34、esign requirements, modes of operation for the exchange of PTP messages, the PTP protocol mapping, the best master clock algorithm (BMCA) options, as well as the PTP protocol configuration parameters. NOTE The parameters defined in the first version of the profile have been chosen based on the case
35、where physical layer frequency support is provided. This Recommendation also specifies some aspects necessary for use in a telecom environment that are outside the scope of, and complement the PTP profile. 2 References The following ITU-T Recommendations and other references contain provisions which
36、, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of app
37、lying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-
38、T G.781 Recommendation ITU-T G.781 (2008), Synchronization layer functions. ITU-T G.810 Recommendation ITU-T G.810 (1996), Definitions and terminology for synchronization networks. ITU-T G.8260 Recommendation ITU-T G.8260 (2015), Definitions and terminology for synchronization in packet networks. IT
39、U-T G.8265.1 Recommendation ITU-T G.8265.1/Y.1365.1 (2014), Precision time protocol telecom profile for frequency synchronization. ITU-T G.8271 Recommendation ITU-T G.8271/Y.1366 (2016), Time and phase synchronization aspects of packet networks. ITU-T G.8271.1 Recommendation ITU-T G.8271.1/Y.1366.1
40、(2013), Network limits for time synchronization in packet networks. ITU-T G.8272 Recommendation ITU-T G.8272/Y.1367 (2012), Timing characteristics of primary reference time clocks. 2 Rec. ITU-T G.8275.1/Y.1369.1 (2016)/Amd.2 (03/2018) ITU-T G.8273 Recommendation ITU-T G.8273/Y.1368 (2013), Framework
41、 of phase and time clocks. ITU-T G.8273.2 Recommendation ITU-T G.8273.2/Y.1368.2 (2014), Timing characteristics of telecom boundary clocks and telecom time slave clocks. ITU-T G.8275 Recommendation ITU-T G.8275/Y.1369 (2013), Architecture and requirements for packet-based time and phase distribution
42、. IEEE 1588 IEEE 1588-2008, IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: The terms and definitions used in this Recommendation are
43、contained in ITU-T G.810 and ITU-T G.8260. 3.2 Terms defined in this Recommendation This Recommendation defines the following term: 3.2.1 special port: A PTP special port is a PTP port that translates between the native timing mechanism of a medium and PTP. 4 Abbreviations and acronyms This Recommen
44、dation uses the following abbreviations and acronyms: AVAR Allan Variance BC Boundary Clock BMCA Best Master Clock Algorithm EEC synchronous Ethernet Equipment Clock ePRTC Enhanced Primary Reference Time Clock EUI Extended Unique Identifier FPM Flicker Phase Modulation GM Grandmaster GNSS Global Nav
45、igation Satellite System LAG Link Aggregation MVAR Modified Allan Variance OC Ordinary Clock PRC Primary Reference Clock PRS Primary Reference Source PRTC Primary Reference Time Clock PSD Power Spectral Density PTP Precision Time Protocol QL Quality Level SDH Synchronous Digital Hierarchy Rec. ITU-T
46、 G.8275.1/Y.1369.1 (2016)/Amd.2 (03/2018) 3 SSM Synchronization Status Message SSU Synchronization Supply Unit SSU-A primary level SSU SSU-B secondary level SSU ST2 Stratum 2 ST3E Stratum 3 Enhanced T-BC Telecom Boundary Clock TC Transparent Clock T-GM Telecom Grandmaster T-TC Telecom Transparent Cl
47、ock T-TSC Telecom Time Slave Clock TLV Type Length Value TVAR Time Variance VLAN Virtual Local Area Network WPM White Phase Modulation 5 Conventions Within this Recommendation, the following conventions are used: the term PTP refers to the PTP version 2 protocol defined in IEEE 1588. PTP messages us
48、ed within this Recommendation are defined in IEEE 1588 and are identified using italicized text. The term telecom boundary clock (T-BC) refers to a device consisting of a boundary clock (BC) as defined in IEEE 1588 and this Recommendation, with additional performance characteristics defined in ITU-T
49、 G.8273.2. The term telecom transparent clock (T-TC) refers to a device consisting of a transparent clock (TC) as defined in IEEE 1588, with additional performance characteristics for further study. The term telecom grandmaster (T-GM) refers to a device consisting of a grandmaster (GM) clock as defined in IEEE 1588 and this Recommendation, with additional performance characteristics for further study. The term telecom time slave clock (T-
