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.8265.1/Y.1365.1 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (07/2014) 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 protocol aspects Transport Precision time protocol telecom profile for frequency synchronization Recommendation ITU-T G.8265.1/Y.1365.1 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS
3、 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 METALLIC LINES G.300G.399 GENERAL CHARA
4、CTERISTICS 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.699 DIGITAL TERMINAL EQUIPMENTS G.700G
5、.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 G.7000G.7999 PACKET OVER TRANSPORT ASPE
6、CTS 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 to the list of ITU-T Recommendations. R
7、ec. ITU-T G.8265.1/Y.1365.1 (07/2014) i Recommendation ITU-T G.8265.1/Y.1365.1 Precision time protocol telecom profile for frequency synchronization Summary Recommendation ITU-T G.8265.1/Y.1365.1 contains the ITU-T precision time protocol (PTP) profile for frequency distribution without timing suppo
8、rt from the network (unicast mode). It provides the necessary details to utilize IEEE 1588 in a manner consistent with the architecture described in Recommendation ITU-T G.8265/Y.1365. This edition of the Recommendation defines the PTP profile for unicast mode only. Future editions of the Recommenda
9、tion will contain a separate profile for a mixed unicast/multicast case. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T G.8265.1/Y.1365.1 2010-10-07 15 11.1002/1000/10911 1.1 ITU-T G.8265.1/Y.1365.1 (2010) Amd. 1 2011-04-13 15 11.1002/1000/11143 1.2 ITU-T G.8265.1/Y.1365.1
10、(2010) Amd. 2 2012-10-29 15 11.1002/1000/11821 2.0 ITU-T G.8265.1/Y.1365.1 2014-07-22 15 11.1002/1000/12193 _ * 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/11.1
11、002/1000/11830-en. ii Rec. ITU-T G.8265.1/Y.1365.1 (07/2014) 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-
12、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), which meets every four ye
13、ars, 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 ITU-Ts purview, the nec
14、essary 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 Recommendation is voluntary. Howev
15、er, 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 “must“ and the negative
16、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 may involve the use of
17、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 this Recommendation, ITU
18、 had 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 database at http:/www.itu.int
19、/ITU-T/ipr/. ITU 2014 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.8265.1/Y.1365.1 (07/2014) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 1 3.1 Terms defined elsewhere 1
20、 3.2 Terms defined in this Recommendation . 1 4 Abbreviations and acronyms 2 5 Conventions 2 6 Use of PTP for frequency distribution 2 6.1 High-level design requirements 3 6.2 General description . 4 6.3 PTP modes 5 6.4 PTP mapping 6 6.5 Message rates 6 6.6 Unicast message negotiation 7 6.7 Alternat
21、e BMCA, telecom slave model and master selection process . 9 6.8 Additional protection functions 14 7 ITU-T PTP profile for frequency distribution without timing support from the network . 15 8 Security aspects 15 Annex A ITU-T PTP profile for frequency distribution without timing support from the n
22、etwork (unicast mode) 16 A.1 Profile identification . 16 A.2 PTP attribute values 16 A.3 PTP options 20 A.4 Best master clock algorithm (BMCA) options . 21 A.5 Path delay measurement option (delay request/delay response) 21 A.6 Configuration management options . 21 A.7 Clock identity format 21 A.8 F
23、lags used by this profile 21 A.9 Control field (controlField) 22 Appendix I Use of mixed unicast/multicast mode for PTP messages 23 Rec. ITU-T G.8265.1/Y.1365.1 (07/2014) 1 Recommendation ITU-T G.8265.1/Y.1365.1 Precision time protocol telecom profile for frequency synchronization 1 Scope This Recom
24、mendation 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 frequency only. The profile is based on the architecture
25、described in ITU-T G.8265 and definitions described in ITU-T G.8260. The first version of the profile specifies the high-level design requirements, modes of operation for the exchange of PTP messages, the PTP protocol mapping, the use of unicast transmission and negotiation, an alternate best master
26、 clock algorithm (BMCA), as well as the PTP protocol configuration parameters. This Recommendation also specifies some aspects necessary for use in a telecom environment which are outside the scope of, and complement the PTP profile. 2 References The following ITU-T Recommendations and other referen
27、ces 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 Recommendation are therefore encouraged to invest
28、igate 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 stat
29、us of a Recommendation. ITU-T G.781 Recommendation ITU-T G.781 (2008), Synchronization layer functions. ITU-T G.8260 Recommendation ITU-T G.8260 (2012), Definitions and terminology for synchronization in packet networks. ITU-T G.8265 Recommendation ITU-T G.8265/Y.1365 (2010), Architecture and requir
30、ements for packet-based frequency delivery. IEEE 1588 IEEE Std 1588-2008, 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: 3.1.1 packet mast
31、er clock ITU-T G.8260 3.1.2 packet slave clock ITU-T G.8260 3.1.3 packet timing signal ITU-T G.8260 3.2 Terms defined in this Recommendation None. 2 Rec. ITU-T G.8265.1/Y.1365.1 (07/2014) 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: BMC Best Master
32、Clock BMCA Best Master Clock Algorithm EUI Extended Unique Identifier GM Grand Master NTP Network Time Protocol OC Ordinary Clock ParentDS Parent Data Set (terminology used in IEEE 1588) LSP Label Switched Path MPLS Multi-Protocol Label Switching PDV Packet Delay Variation PTP Precision Time Protoco
33、l PTSF Packet Timing Signal Fail QL Quality Level SDH Synchronous Digital Hierarchy SOOC Slave-Only Ordinary Clock SSM Synchronization Status Message SyncE Synchronous Ethernet TLV Type Length Value UDP User Datagram Protocol VLAN Virtual Local Area Network 5 Conventions Within this Recommendation,
34、the following conventions are used: the term PTP refers to the PTP version 2 protocol defined in IEEE 1588. The term “slave“ or “slave clock“ refers to a “slave-only ordinary clock“ (SOOC) as defined in clause 9.2.2 of IEEE 1588. A “Telecom Slave“ is a device consisting of one or more SOOCs. The ter
35、m “master“ or “packet master“ or “packet master clock“ refers to a grand master as defined in IEEE 1588. PTP messages used within this Recommendation are defined in IEEE-1588 and are identified using italicized text. 6 Use of PTP for frequency distribution IEEE 1588 has been developed by the IEEE in
36、itially to support the timing requirements of industrial automation. The IEEE 1588 standard contains the precision time protocol (PTP) that was designed to enable accurate time transfer. Subsequent to the publication of the first version of the standard, work began on developing a second version of
37、the standard which contains features useful to the transport of the protocol over a wide area network. This “Version 2“ of IEEE 1588 also introduces the concept of the “profile“, whereby aspects of the protocol may be selected and specified for a particular use other than the originally intended ind
38、ustrial automation. This Recommendation defines the “profile for telecom“ applications in order to support the specific architectures described in ITU-T G.8265. Rec. ITU-T G.8265.1/Y.1365.1 (07/2014) 3 In order to claim compliance with the telecom profile, the requirements of this Recommendation and
39、 the relevant requirements of IEEE 1588, as referenced in Annex A, must be met. The detailed aspects related to the telecom profile are described in the following clauses, while the profile itself is contained in Annex A. It follows the general rules for profile specification developed in IEEE 1588.
40、 The IEEE 1588 telecom profile defined within this Recommendation is intended to be used by applications that need frequency synchronization only. It does not cover applications where there is need for phase alignment and/or time of the day. This profile addresses the case where the PTP masters and
41、slaves will be used in networks where there is no support for the PTP protocol in any intermediate node between the PTP master and the PTP slave. It is also important to note that the default PTP protocol is based on multicast. This profile uses only the unicast mode. The use of mixed unicast/multic
42、ast operation is for further study. This PTP telecom profile defines the IEEE 1588 parameters to be used in order to guarantee protocol interoperability between implementations and specifies the optional features, default values of configurable attributes and mechanisms that must be supported. Howev
43、er, it does not guarantee that the performance requirements of a given application will be met. Those performance aspects are currently under study, and imply additional elements beyond the content of the PTP profile itself. 6.1 High-level design requirements IEEE 1588 states in clause 19.3.1.1: “Th
44、e purpose of a PTP profile is to allow organizations to specify specific selections of attribute values and optional features of PTP that, when using the same transport protocol, inter-work and achieve a performance that meets the requirements of a particular application.“ For operation in the telec
45、om network, some additional criteria are also required to be consistent with standard telecom synchronization practices. With that in mind, high-level objectives for the PTP profile for frequency distribution are: 1) To allow interoperability between PTP master clocks and PTP slave clocks compliant
46、with the profile. This means that PTP master clocks compliant with the profile must have the ability to serve multiple PTP slave clocks from different vendors, and slaves require the ability to derive synchronization from one or more masters from different vendors. 2) To permit operation over manage
47、d, wide-area packet-based telecom networks. This may include networks based on protocols such as Ethernet, IP and multi-protocol label switching (MPLS), and combinations thereof. 3) To define message rates and parameter values consistent with frequency distribution to the required performance for te
48、lecom applications. Note that the profile does not guarantee meeting performance criteria by itself, but should permit the desired performance, given competently designed equipment operating over a suitably designed and managed packet network. 4) To allow interoperability with existing synchronizati
49、on networks (such as synchronous Ethernet (SyncE) and synchronous digital hierarchy (SDH). In particular, this means that the profile must define the means to support the transmission of the ITU-T G.781 quality level (QL) values from packet master clock to packet slave clock, providing full traceability back to a primary reference. The QL levels transmitted must be consistent with the existing synchronization practice, and the performance of clocks in the synchroniza
