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.8266/Y.1376 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 1 (03/2018) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Packet over Transport aspects Synchronization, quality and availabil
2、ity targets SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS, NEXT-GENERATION NETWORKS, INTERNET OF THINGS AND SMART CITIES Internet protocol aspects Transport Timing characteristics of telecom grandmaster clocks for frequency synchronization Amendment 1 Recommendation ITU-T G.
3、8266/Y.1376 (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 G.200G.299 INDIVIDUAL CHARACTERISTICS OF
4、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 TELEPHONY G.450G.499 TRANSMISSION MEDIA
5、 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 TRANSMISSION MEDIA CHARACTERISTICS G.6000
6、G.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.90
7、00G.9999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.8266/Y.1376 (2016)/Amd.1 (03/2018) i Recommendation ITU-T G.8266/Y.1376 Timing characteristics of telecom grandmaster clocks for frequency synchronization Amendment 1 Summary Recommendation ITU-T G.8266/Y.1
8、376 specifies the requirements for packet master clocks suitable for frequency synchronization in packet networks. Amendment 1 provides the following updates: Changes the scope to include the grandmaster (GM) with embedded primary reference time clock (PRTC); Changes clause 8.1 to account for the GM
9、 with embedded PRTC; Replaces text and provides additional material to Appendix I. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T G.8266/Y.1376 2016-11-13 15 11.1002/1000/13106 1.1 ITU-T G.8266/Y.1376 (2016) Amd. 1 2018-03-16 15 11.1002/1000/13548 Keywords Frequency synchro
10、nization, packet master clock. * 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.8266/Y.1376 (2016)/Amd.1 (03/2018) FOREWORD
11、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 for studying tech
12、nical, 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 study groups which,
13、 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 with ISO and IE
14、C. 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 provisions (to en
15、sure, 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 of such words do
16、es 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 position concernin
17、g 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, protected by patent
18、s, 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 2018 All rights reserved. No part of this publica
19、tion may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T G.8266/Y.1376 (2016)/Amd.1 (03/2018) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 2 4 Abbreviations and acronyms 2 5 Conventions 2 6 Frequency accuracy 2 7 Pull-in, hold-
20、in, and pull-out ranges . 2 8 Noise generation . 3 8.1 Wander in locked mode 3 8.2 Jitter 3 9 Noise tolerance . 3 9.1 Wander tolerance 3 9.2 Jitter tolerance 3 10 Noise transfer 3 11 Transient response and holdover performance . 4 11.1 Short-term phase transient response . 4 11.2 Long-term phase tra
21、nsient response (hold-over) 4 11.3 Phase discontinuity . 4 12 Interfaces . 4 Annex A Telecom grandmaster clock functional model 5 Appendix I Measurement method for wander transfer . 7 Rec. ITU-T G.8266/Y.1376 (2016)/Amd.1 (03/2018) 1 Recommendation ITU-T G.8266/Y.1376 Timing characteristics of telec
22、om grandmaster clocks for frequency synchronization Amendment 1 Editorial note: This is a complete-text publication. Modifications introduced by this amendment are shown in revision marks relative to Recommendation ITU-T G.8266/Y.1376 (2016). 1 Scope This Recommendation defines the minimum requireme
23、nts for the timing functions of the telecom grandmaster clocks that operate in the network architecture as defined in ITU-T G.8265 and the related profile defined in ITU-T G.8265.1. It supports frequency synchronization distribution when using packet-based methods. It allows for proper network opera
24、tion when a telecom grandmaster clock is timed from a physical frequency source traceable to a primary reference clock (PRC) or primary reference time clock (PRTC) according to the architecture defined in ITU-T G.803. The case of a telecom grandmaster whose frequency is provided by an embedded PRTC
25、or PRC function is for further study. This Recommendation focuses on the types of networks corresponding to the HRM-1 and HRM-2 as defined in ITU-T G.8261.1. The HRM-2 type of network is for further study in the current version of this Recommendation. Other types of networks are out of the scope of
26、this Recommendation. This Recommendation includes clock accuracy, noise tolerance, noise transfer, noise generation, and holdover specifications for the telecom grandmaster clocks for frequency synchronization. These requirements apply under the normal environmental conditions specified for the equi
27、pment. 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 time of publication, the editions indicated were valid. All Recommendations and other references are subject to
28、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 list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within
29、this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T G.703 Recommendation ITU-T G.703 (2016), Physical/electrical characteristics of hierarchical digital interfaces. ITU-T G.803 Recommendation ITU-T G.803 (2000), Architecture of transport networks ba
30、sed on the synchronous digital hierarchy (SDH). ITU-T G.810 Recommendation ITU-T G.810 (1996), Definitions and terminology for synchronization networks. ITU-T G.812 Recommendation ITU-T G.812 (2004), Timing requirements of slave clocks suitable for use as node clocks in synchronization networks. ITU
31、-T G.8260 Recommendation ITU-T G.8260 (2015), Definitions and terminology for synchronization in packet networks. 2 Rec. ITU-T G.8266/Y.1376 (2016)/Amd.1 (03/2018) ITU-T G.8261.1 Recommendation ITU-T G.8261.1 (2012), Packet delay variation network limits applicable to packet based methods (Frequency
32、 synchronization). ITU-T G.8262 Recommendation ITU-T G.8262 (2015), Timing characteristics of a synchronous Ethernet equipment slave clock. ITU-T G.8265 Recommendation ITU-T G.8265 (2010), Architecture and requirements for packet-based frequency delivery. ITU-T G.8265.1 Recommendation ITU-T G.8265.1
33、 (2014), Precision time protocol telecom profile for frequency synchronization. ITU-T G.8272 Recommendation ITU-T G.8272 (2015), Timing characteristics of primary reference time clocks. 3 Definitions The terms and definitions used in this Recommendation are contained in ITU-T G.810 and ITU-T G.8260.
34、 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: GM Grandmaster GNSS Global Navigation Satellite System MTIE Maximum Time Interval Error NE Network Element PEC-M-F Packet-based Equipment Clock Master Frequency PRC Primary Reference Clock PRTC Primary R
35、eference Time Clock PTP Precision Time Protocol SyncE Synchronous Ethernet TDEV Time Deviation ToD Time of Day 5 Conventions The telecom grandmaster clock for frequency synchronization (PEC-M-F) is based on ITU-T G.812. The packet-based equipment clock master frequency (PEC-M-F) conforms to one of I
36、TU-T G.812 Type I, Type II or Type III specifications with additional requirements or modifications as listed in this recommendation: A PEC-M-F Type I is based on ITU-T G.812 Type I A PEC-M-F Type II is based on ITU-T G.812 Type II A PEC-M-F Type III is based on ITU-T G.812 Type III. 6 Frequency acc
37、uracy The PEC-M-F should comply with ITU-T G.812 clause 6 for its respective clock Type. Rec. ITU-T G.8266/Y.1376 (2016)/Amd.1 (03/2018) 3 7 Pull-in, hold-in, and pull-out ranges The PEC-M-F should comply with ITU-T G.812 clause 7 for its respective clock Type. 8 Noise generation 8.1 Wander in locke
38、d mode The PEC-M-F should comply with ITU-T G.812 clause 8.1 for its respective clock Type. The PEC-M-F PTP port output is measured through a first order low-pass filter with bandwidth of 0.1 Hz, and only observation intervals above 1s are considered. For the case of telecom grandmaster whose freque
39、ncy is provided by an embedded PRTC, the PEC-M-F should comply with clause 6.2 of ITU-T G.8272. 8.2 Jitter A PEC-M-F operating in a locked mode synchronized to a noise-free frequency reference at the SyncE/SDH input, should comply with: ITU-T G.812 clause 8.3.1, when measured at a 2048 kHz or 2048 k
40、bit/s output interface ITU-T G.812 clause 8.3.2, when measured at a 1544 kbit/s output interface Peak-to-peak time error of less than 70 ns, when measured at a precision time protocol (PTP) output interface through first-order high-pass filter of 0.1 Hz over a measurement interval of 1000 s. 9 Noise
41、 tolerance 9.1 Wander tolerance The measurement method of clause 9.1.3 is recommended for wander tolerance testing. 9.1.1 MTIE wander tolerance The PEC-M-F complies with ITU-T G.812 clause 9.1.1 for its respective clock Type. 9.1.2 TDEV wander tolerance The PEC-M-F complies with ITU-T G.812 clause 9
42、.1.2 for its respective clock Type. 9.1.3 Sinusoidal wander tolerance The PEC-M-F complies with ITU-T G.812 clause 9.1.3 for its respective clock Type. 9.2 Jitter tolerance The PEC-M-F should comply with the jitter tolerance requirements of: ITU-T G.812 clause 9.2.1, applied at a 2048 kHz or 2048 kb
43、it/s input interface ITU-T G.812 clause 9.2.2, applied at a 1544 kbit/s input interface ITU-T G.8262 clause 9.2, applied at a synchronous Ethernet input interface. 10 Noise transfer The PEC-M-F should comply with ITU-T G.812 clause 10 (a) for its respective clock Type. Guidance on the measurement te
44、chniques for these requirements is given in Appendix I. NOTE The noise transfer measurement technique must account for the allowed noise generation (e.g., wander and timestamp noise) of the clock. 4 Rec. ITU-T G.8266/Y.1376 (2016)/Amd.1 (03/2018) 11 Transient response and holdover performance In eac
45、h of the following clauses, the PEC-M-F PTP output interface is measured through a first order low-pass filter with bandwidth of 0.1 Hz, and only observation intervals above 1 s are considered. 11.1 Short-term phase transient response If the frequency reference of a PEC-M-F Type I clock is a physica
46、l layer clock, the output 2048 kHz and 2048 kbit/s interfaces should comply with the requirements of ITU-T G.812 clause 11.1.1. The output PTP interface should also comply with the 2048 kHz and 2048 kbit/s requirements of ITU-T G.812 clause 11.1.1. The output SyncE interface should comply with the S
47、TM-N requirements of ITU-T G.812 clause 11.1.2. If the frequency reference of a PEC-M-F Type II or Type III clock is a physical layer clock, the output 1544 kbit/s interface should comply with the requirements of ITU-T G.812 clause 11.1.3. The output PTP interface should also comply with the 1544 kb
48、it/s requirements of ITU-T G.812 clause 11.1.3. The output SyncE interface should comply with the STM-N requirements of ITU-T G.812 clause 11.1.4. 11.2 Long-term phase transient response (hold-over) The PEC-M-F should comply with ITU-T G.812 clause 11.2 for its respective clock Type. 11.3 Phase disc
49、ontinuity The PEC-M-F should comply with ITU-T G.812 clause 11.4 for its respective clock Type. 12 Interfaces The requirements in this Recommendation are related to reference points internal to the network elements (NEs) in which the clock is embedded and are therefore not necessarily available for measurement or analysis by the user. Therefore the performance of the ITU-T G.812 clock is not defined at these internal referen
