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 (11/2016) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Packet over Transport aspects Synchronization, quality and availability targets
2、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 Recommendation ITU-T G.8266/Y.1376 ITU-T G-SERI
3、ES 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 INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON
4、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 AND OPTICAL SYSTEMS CHARACTERISTICS G.600G
5、.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.6999 DATA OVER TRANSPORT GENERIC ASPECTS
6、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.9000G.9999 For further details, please refer
7、to the list of ITU-T Recommendations. Rec. ITU-T G.8266/Y.1376 (11/2016) i Recommendation ITU-T G.8266/Y.1376 Timing characteristics of telecom grandmaster clocks for frequency synchronization Summary Recommendation ITU-T G.8266/Y.1376 specifies the requirements for packet master clocks suitable for
8、 frequency synchronization in packet networks. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T G.8266/Y.1376 2016-11-13 15 11.1002/1000/13106 Keywords Frequency synchronization, packet master clock. * To access the Recommendation, type the URL http:/handle.itu.int/ in the ad
9、dress 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 (11/2016) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunicati
10、ons, 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 standardizing telecommunication
11、s 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 covered by the procedure lai
12、d 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 indicate both a telecommunica
13、tion 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 achieved when all of these mand
14、atory 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. INTELLECTUAL PROPERTY RIGHTSITU draws a
15、ttention 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 asserted by ITU members or ot
16、hers 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 cautioned that this may not represe
17、nt the latest information and are therefore strongly urged to consult the TSB patent database 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.8266/Y.1376 (
18、11/2016) 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-in, and pull-out ranges . 2 8 Noise generation . 2 8.1 Wander in locked mode 2 8.2 Jitter 3 9 Noise tolerance . 3 9.1 Wander toleranc
19、e 3 9.2 Jitter tolerance 3 10 Noise transfer 3 11 Transient response and holdover performance . 3 11.1 Short-term phase transient response . 3 11.2 Long-term phase transient response (hold-over) 4 11.3 Phase discontinuity . 4 12 Interfaces . 4 Annex A Telecom Grandmaster clock functional model 5 App
20、endix I Measurement method for wander transfer . 7 Rec. ITU-T G.8266/Y.1376 (11/2016) 1 Recommendation ITU-T G.8266/Y.1376 Timing characteristics of telecom grandmaster clocks for frequency synchronization 1 Scope This Recommendation defines the minimum requirements for the timing functions of the t
21、elecom 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 operation when a telecom grandmaster clock
22、 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 or PRC function is for further study.
23、 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 this Recommendation. This Recommendat
24、ion 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 equipment. 2 References The following ITU
25、-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 revision; users of this Recommendatio
26、n 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 this Recommendation does not give it,
27、 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 based on the synchronous digital hierar
28、chy (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-T G.8260 Recommendation ITU-T G.8260
29、 (2015), Definitions and terminology for synchronization in packet networks. ITU-T G.8261.1 Recommendation ITU-T G.8261.1 (2012), Packet delay variation network limits applicable to packet based methods (Frequency synchronization). ITU-T G.8262 Recommendation ITU-T G.8262 (2015), Timing characterist
30、ics of a synchronous Ethernet equipment slave clock. 2 Rec. ITU-T G.8266/Y.1376 (11/2016) 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 (2014), Precision time protocol telecom profile f
31、or frequency synchronization. 3 Definitions The terms and definitions used in this Recommendation are contained in ITU-T G.810 and ITU-T G.8260. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: GNSS Global Navigation Satellite System MTIE Maximum Time I
32、nterval Error NE Network Element PEC-M-F Packet-based Equipment Clock Master Frequency PRC Primary Reference Clock PRTC Primary Reference Time Clock PTP Precision Time Protocol SyncE Synchronous Ethernet TDEV Time Deviation ToD Time of Day 5 Conventions The telecom grandmaster clock for frequency sy
33、nchronization (PEC-M-F) is based on ITU-T G.812. The packet-based equipment clock master frequency (PEC-M-F) conforms to one of ITU-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.
34、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 accuracy The PEC-M-F should comply with ITU-T G.812 clause 6 for its respective clock Type. 7 Pull-in, hold-in, and pull-out ranges The PEC-M-F should comply with ITU-T G.812
35、 clause 7 for its respective clock Type. 8 Noise generation 8.1 Wander in locked mode The PEC-M-F should comply with ITU-T G.812 clause 8.1 for its respective clock Type. Rec. ITU-T G.8266/Y.1376 (11/2016) 3 The PEC-M-F PTP port output is measured through a first order low-pass filter with bandwidth
36、 of 0.1 Hz, and only observation intervals above 1s are considered. 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 kbit/s output interface ITU-T
37、 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 tolerance 9.1 Wander tolera
38、nce 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 9.1.2 for its respective cloc
39、k 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 kbit/s input interface ITU-T G
40、.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 techniques for these requireme
41、nts 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. 11 Transient response and holdover performance In each of the following clauses, the PEC-M-F PTP output interface is measured throu
42、gh 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 physical layer clock, the output 2048 kHz and 2048 kbit/s interfaces should comply wi
43、th 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 4 Rec. ITU-T G.8266/Y.1376 (11/2016) ITU-T G.812 clause 11.1.1. The output SyncE interface should comply with the STM-N requirements of ITU-T G.812 clause 1
44、1.1.2. 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 kbit/s requirements of ITU-T G.812 clause 1
45、1.1.3. 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 discontinuity The PEC-M-F should comply with
46、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. Ther
47、efore the performance of the ITU-T G.812 clock is not defined at these internal reference points, but rather at the external interfaces of the equipment. Note that not all of the interfaces below need to be implemented on all equipment. The external input and output are: 2 048 kHz interfaces accordi
48、ng to ITU-T G.703 with additional jitter and wander requirements as specified herein; 2 048 kbit/s interfaces according to ITU-T G.703 with additional jitter and wander requirements as specified herein; 1 544 kbit/s interfaces according to ITU-T G.703 with additional jitter and wander requirements a
49、s specified herein; Ethernet interface carrying PTP messages; NOTE 1 This interface is only used for output. Synchronous Ethernet (SyncE) interfaces; NOTE 2 Ethernet interfaces can combine Synchronous Ethernet for frequency and PTP messages. Other interfaces are for further study. Rec. ITU-T G.8266/Y.1376 (11/2016) 5 Annex A Telecom Grandmaster clock functional model (This annex forms an integral part of this Recommen
