ITU-T G 8275 1-2016 Internet protocol aspects – Transport Precision time protocol telecom profile for phase time synchronization with full timing support from the network (Study Gr.pdf

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 (06/2016) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Packet over Transport aspects Synchronization, quality and availability targ

2、ets SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND 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 Recommenda

3、tion ITU-T G.8275.1/Y.1369.1 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.200G.299 INDIVIDUAL CHARACTERISTICS OF IN

4、TERNATIONAL 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 TELEPHONY G.450G.499 TRANSMISSION MEDIA A

5、ND 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 TRANSMISSION MEDIA CHARACTERISTICS G.6000G.

6、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 Management G.8600G.8699 ACCESS NETWORKS G.9000

7、G.9999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.8275.1/Y.1369.1 (06/2016) i 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 Summary Recommendation ITU-T

8、 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 the architecture described in Recommendation ITU-T G.8275/Y.1369.

9、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 Keywords Full timing support, IEEE 1588,

10、 phase and time synchronization, PTP, telecom profile. * To access the Recommendation, type the URL http:/handle.itu.int/ 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 (06/

11、2016) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in 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 fo

12、r studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing 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 stud

13、y groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is 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

14、with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory pr

15、ovisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved 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 o

16、f such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL 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 pos

17、ition concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether 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, prot

18、ected by patents, which may be required to implement this Recommendation. However, implementers are cautioned 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 2016 All rights reserved. No part

19、of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T G.8275.1/Y.1369.1 (06/2016) 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 Abb

20、reviations and acronyms 2 5 Conventions 3 6 Use of PTP for phase/time distribution 3 6.1 High-level design requirements 4 6.2 PTP modes and options 4 6.3 Protection aspects and Alternate BMCA 7 6.4 Phase/time traceability information 14 7 ITU-T PTP profile for phase/time distribution with full timin

21、g support from the network . 16 8 Security aspects 16 Annex A ITU-T PTP profile for phase/time distribution with full timing support from the network . 17 A.1 Profile identification . 17 A.2 PTP attribute values 17 A.3 PTP options 22 A.4 Best master clock algorithm options 23 A.5 Path delay measurem

22、ent option (delay request/delay response) 23 A.6 Clock identity format 23 A.7 Configuration management options . 23 A.8 Security aspects 23 A.9 Other optional features of IEEE 1588 23 A.10 PTP common header flags 23 Annex B Options to establish the PTP topology with the Alternate BMCA 25 Annex C Inc

23、lusion of an external phase/time input interface in a T-BC 26 Annex D Path trace (optional) 27 Annex E Synchronization uncertain indication (optional) 28 Annex F Use of stepsRemoved to limit reference chain (optional) 29 Appendix I Considerations on the use of transparent clock 30 Appendix II Consid

24、erations on the transmission of Delay_Req messages . 31 Appendix III Considerations on the choice of the PTP Ethernet multicast destination address 33 Appendix IV Considerations on the use of priority2 34 iv Rec. ITU-T G.8275.1/Y.1369.1 (06/2016) Page Appendix V Description of PTP clock states and a

25、ssociated contents of Announce messages . 35 V.1 Purpose of the appendix . 35 V.2 Description of the states . 35 V.3 Example of mapping between PTP port states and PTP clock states for a 3-port T-BC 37 V.4 T-GM Announce message contents based on the internal PTP clock states 38 V.5 T-BC Announce mes

26、sage contents based on the internal PTP clock states . 39 Appendix VI Operations over link aggregation 40 Appendix VII Relationship between clockClass and holdover specification . 41 Appendix VIII Considerations on a T-TSC connected to an end application 43 Appendix IX Calculation of offsetScaledLog

27、Variance for T-GM timed by PRTC or ePRTC. 44 IX.1 Observation interval and TDEV noise generation 44 IX.2 Computation of PTP variance from TDEV 44 IX.3 Computation of offsetScaledLogVariance from PTP variance 45 Bibliography. 47 Rec. ITU-T G.8275.1/Y.1369.1 (06/2016) 1 Recommendation ITU-T G.8275.1/Y

28、.1369.1 Precision time protocol telecom profile for phase/time synchronization with full timing support from the network 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

29、that are necessary to ensure 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 spe

30、cifies the high-level design 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 ch

31、osen based on the case 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 c

32、ontain provisions which, 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

33、 the possibility of applying 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

34、 a Recommendation. ITU-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

35、 in packet networks. ITU-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.8271.1 Recommendation ITU-T G.8271.1/Y.1366.1 (2013), Network limits for time synchronization in packet networks. ITU-T G.8272 Recommendat

36、ion ITU-T G.8272/Y.1367 (2012), Timing characteristics of primary reference time clocks. ITU-T G.8273 Recommendation ITU-T G.8273/Y.1368 (2013), Framework 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 tel

37、ecom 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. 2 Rec. ITU-T G.8275.1/Y.1369.1 (06/2016) IEEE 1588 IEEE 1588-2008, IEEE Standard for a Precision Clock Synchronization Protocol for Networked Me

38、asurement 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 contained in ITU-T G.810 and ITU-T G.8260. 3.2 Terms defined in this Recommendation None. 4 Abbreviations

39、 and acronyms This Recommendation 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

40、Grandmaster GNSS Global Navigation 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 D

41、igital Hierarchy 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 Rec. ITU-T G.8275.1/Y.1369.1 (06/2016) 3 TC Transparent Clock T-GM Telecom Grandmaster T-TC Telecom

42、Transparent Clock 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. P

43、TP messages used 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 de

44、fined in ITU-T 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)

45、 clock as defined in IEEE 1588 and this Recommendation, with additional performance characteristics for further study. The term telecom time slave clock (T-TSC) refers to a device consisting of a slave-only ordinary clock (OC) as defined in IEEE 1588 and this Recommendation, with additional performa

46、nce characteristics defined in the Annex C of ITU-T G.8273.2. The term primary reference time clock (PRTC) refers to the clock defined in ITU-T G.8272. The term enhanced primary reference time clock (ePRTC) refers to an enhanced version of the PRTC, which is being studied. 6 Use of PTP for phase/tim

47、e distribution The 2002 version of the IEEE 1588 was developed by the IEEE initially to support the timing requirements of industrial automation, and defines the precision time protocol (PTP) designed to enable accurate time transfer in this context. The 2008 version of IEEE 1588 (defined in IEEE 15

48、88) contains features useful to the transport of the protocol over a wide area network, and introduces the concept of “profile“, whereby aspects of the protocol may be selected and specified for a particular use other than the originally intended industrial automation. A PTP profile has been defined

49、 in ITU-T G.8265.1 to address applications requiring frequency synchronization only. This Recommendation defines another PTP profile, for telecom applications requiring accurate phase and time synchronization. It supports the specific architecture described in ITU-T G.8275 in order to allow the distribution of phase/time with full timing support from the network, and is based on the 2008 version of PTP defined in IEEE 1588. In order to claim com