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.8275.2/Y.1369.2 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 1 (08/2017) 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 partial timing support from the networ
3、k Amendment 1 Recommendation ITU-T G.8275.2/Y.1369.2 (2016) Amendment 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
4、G.200G.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 LIN
5、E TELEPHONY 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
6、TRANSMISSION 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 Man
7、agement G.8600G.8699 ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.8275.2/Y.1369.2 (2016)/Amd.1 (08/2017) i Recommendation ITU-T G.8275.2/Y.1369.2 Precision time protocol telecom profile for phase/time synchronization with partial t
8、iming support from the network Amendment 1 Summary Recommendation ITU-T G.8275.2/Y.1369.2 contains the ITU-T precision time protocol (PTP) profile for phase/time distribution with partial timing support from the network (unicast mode). It provides the necessary details to utilize IEEE 1588 in a mann
9、er consistent with the architecture described in Recommendation ITU-T G. 8275/Y.1369. This Recommendation defines the PTP profile for unicast mode only. Future editions of this Recommendation may contain a separate profile for a mixed unicast/multicast case. Amendment 1 provides the following update
10、s: Updates Scope and References Modifies clauses 6.6, 6.7.9, 6.7.11, 6.8, A.10 Adds Annex F, Mapping from PTP clockClass values to Quality Levels Adds Appendix III, PTP Monitoring Backup Scenario Example Adds Appendix IV, Description of PTP clock states and associated contents of Announce messages A
11、dds Appendix V, BMCA cycling between masters Adds Appendix VI, Considerations of PTP over IP transport in ring topologies. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T G.8275.2/Y.1369.2 2016-06-22 15 11.1002/1000/12833 1.1 ITU-T G.8275.2/Y.1369.2 (2016) Amd. 1 2017-08-29
12、15 11.1002/1000/13330 Keywords IEEE 1588, partial timing support, 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.it
13、u.int/11.1002/1000/11830-en. ii Rec. ITU-T G.8275.2/Y.1369.2 (2016)/Amd.1 (08/2017) 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 Stand
14、ardization 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 standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), wh
15、ich 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 covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within
16、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 indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendat
17、ion is voluntary. However, the Recommendation may contain certain mandatory provisions (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 “
18、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. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the possibility that the practice or implementation of this Recommendation
19、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 asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of t
20、his Recommendation, ITU had not received notice of intellectual property, protected 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 da
21、tabase at http:/www.itu.int/ITU-T/ipr/. ITU 2017 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T G.8275.2/Y.1369.2 (2016)/Amd.1 (08/2017) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Def
22、initions 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 4 6.1 High-level design requirements 5 6.2 PTP modes and options 5 6.3 PTP modes 7 6.4 PTP mapping 8 6.5 Message rates 8 6.6 U
23、nicast message negotiation 9 6.7 Alternate BMCA, telecom slave model and master selection process . 11 6.8 Phase/time traceability information 20 6.9 Use of alternate master flag 22 7 ITU-T PTP profile for phase/time distribution with partial timing support from the network . 22 8 Security aspects 2
24、2 Annex A ITU-T PTP profile for time distribution with partial timing support from the network (unicast mode) 23 A.1 Profile identification . 23 A.2 PTP attribute values 23 A.3 PTP options 28 A.4 Best master clock algorithm options 29 A.5 Path delay measurement option (delay request/delay response)
25、29 A.6 Configuration management options . 29 A.7 Clock identity format 29 A.8 Security aspects 29 A.9 Other optional features of IEEE 1588 29 A.10 PTP common header flags 29 Annex B Options to establish the PTP topology with the Alternate BMCA 32 Annex C Inclusion of an external phase/time input int
26、erface on a PTP clock 33 Annex D TLV for PTP interface rate (optional) . 34 Annex E Synchronization uncertain indication (optional) 36 Annex F Mapping from PTP clockClass values to quality levels. 37 iv Rec. ITU-T G.8275.2/Y.1369.2 (2016)/Amd.1 (08/2017) Page Appendix I Considerations on the use of
27、priority2 . 39 Appendix II Considerations on a T-TSC-A or T-TSC-P connected to an end application 40 Appendix III PTP monitoring backup scenario example 41 Appendix IV Description of PTP clock states and associated contents of Announce messages . 43 IV.1 Purpose of the appendix . 43 IV.2 Description
28、 of the states . 43 IV.3 Example of mapping between PTP port states and PTP clock states for a 3-port T-BC 45 IV.4 T-GM Announce message contents based on the internal PTP clock states 46 IV.5 T-BC Announce message contents based on the internal PTP clock states . 47 Appendix V BMCA cycling between
29、masters 50 V.1 Scenario where a PTP clocks BMCA cycles between two masters 50 V.2 Approaches to avoid a PTP clocks BMCA from cycling between two masters 51 Appendix VI Considerations of PTP over IP transport in ring topologies . 52 Rec. ITU-T G.8275.2/Y.1369.2 (2016)/Amd.1 (08/2017) 1 Recommendation
30、 ITU-T G.8275.2/Y.1369.2 Precision time protocol telecom profile for phase/time synchronization with partial timing support from the network Amendment 1 Editorial note: This is a complete-text publication. Modifications introduced by this amendment are shown in revision marks relative to Recommendat
31、ion ITU-T G.8275.2/Y.1369.2 (2016). 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 ensure network element interoperability for the delivery of acc
32、urate phase/time (and frequency) synchronization. The profile is based on the partial timing support (PTS) from the network architecture as described in ITU-T G.8275 and definitions described in ITU-T G.8260. It is assumed that this profile will be used in well-planned cases where network behaviour
33、and performance can be constrained within well-defined limits, including limits on static asymmetry. Control of static asymmetries can be achieved in case of assisted partial timing support. Use of this profile in non-assistedunassisted mode would require careful considerations on how to control sta
34、tic asymmetries. Additional considerations are included in ITU-T G.8271.2.This version of the profile specifies 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 protoc
35、ol configuration parameters. This version of the profile specifies 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. Further informat
36、ion on the setup of the protocol in the network is planned to be included in future versions of this Recommendation. In particular, this information will be related to architectures that imply rearrangements of the synchronization direction, and to architectures that include clocks with multiple PTP
37、 ports, especially when ports not in the MASTER state provide synchronization services. At the time of publication of this profile, performance analysis, network limits, and clocks used in the profile, namely boundary and slave clocks, are for further study. This Recommendation also specifies some a
38、spects necessary for use in a telecom environment that are outside the scope of the PTP profile, but complement it. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the tim
39、e 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 applying the most recent edition of the Recommendations and other references listed below. A
40、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-T G.781 Recommendation ITU-T G.781 (2008), Synchronization layer functions. ITU-T G.810 Re
41、commendation ITU-T G.810 (1996), Definitions and terminology for synchronization networks. 2 Rec. ITU-T G.8275.2/Y.1369.2 (2016)/Amd.1 (08/2017) ITU-T G.8260 Recommendation ITU-T G.8260 (2015), Definitions and terminology for synchronization in packet networks. ITU-T G.8265.1 Recommendation ITU-T G.
42、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.8271.2 Recommendation ITU-T G.8271.2/Y.1366.2 (2017), Network limits for time sync
43、hronization in packet networks with partial timing support from the network. ITU-T G.8272 Recommendation 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 Rec
44、ommendation 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), Time and phase distribution through packet networks. ITU-T G.8275.1 Recommendation ITU-T G.8275.1/Y.1369.1 (2016), Prec
45、ision time protocol telecom profile for phase/time synchronization with full timing support from the network. 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 Recomme
46、ndation 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 and acronyms This Recommendation uses the following abbreviations and acronyms: APTS
47、 Assisted Partial Timing Support BC Boundary Clock BMCA Best Master Clock Algorithm ePRTC Enhanced Primary Reference Time Clock EUI Extended Unique Identifier GM GrandMaster GNSS Global Navigation Satellite System IP Internet Protocol Rec. ITU-T G.8275.2/Y.1369.2 (2016)/Amd.1 (08/2017) 3 OC Ordinary
48、 Clock ParentDS Parent Data Set PDV Packet Delay Variation PRC Primary Reference Clock PRS Primary Reference Source PRTC Primary Reference Time Clock PTP Precision Time Protocol PTPVAR PTP Variance PTS Partial Timing Support PTSF Packet Timing Signal Fail QL Quality Level SDH Synchronous Digital Hie
49、rarchy SF Signal Fail 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-P Partial-Support Telecom Boundary Clock TC Transparent Clock T-GM Telecom Grandmaster TLV Type, Length, Value T-TC-P Partial-Support Telecom Transparent Clock T-TSC-A Assisted Partial-Support Telecom Time Slave Clock T-TSC-P Partial-Support Telecom Time Slave Clock UDP User
