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/Y.1369 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 2 (04/2016) 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 AND NEXT-GENERATION NETWORKS, INTERNET OF THINGS AND SMART CITIES Internet protocol aspects Transport Architecture and requirements for packet-based time and phase distribution Amendment 2 Recommendation ITU-T G.8275/
3、Y.1369 (2013) Amendment 2 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 INTER
4、NATIONAL 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 AND
5、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.699
6、9 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.9000G.9
7、999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.8275/Y.1369 (2013)/Amd.2 (04/2016) i Recommendation ITU-T G.8275/Y.1369 Architecture and requirements for packet-based time and phase distribution Amendment 2 Summary Amendment 2 to Recommendation ITU-T G.8275/Y
8、.1369 (2013) adds support for precision time protocol (PTP) transparent clocks (TCs) to the architecture and adds an informative appendix on alternate best master clock algorithm (BMCA) operation in ring topologies. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T G.8275/Y.13
9、69 2013-11-22 15 11.1002/1000/12011 1.1 ITU-T G.8275/Y.1369 (2013) Amd. 1 2015-01-13 15 11.1002/1000/12396 1.2 ITU-T G.8275/Y.1369 (2013) Amd. 2 2016-04-13 15 11.1002/1000/12814 _ * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by
10、 the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T G.8275/Y.1369 (2013)/Amd.2 (04/2016) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communicat
11、ion 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 telecommunications on a worldwide basis. The Wor
12、ld 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 laid down in WTSA Resolution 1. In
13、 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 telecommunication administration and a recog
14、nized 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 mandatory provisions are met. The w
15、ords “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 attention to the possibility tha
16、t 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 others outside of the Recommendat
17、ion 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 represent the latest information and a
18、re therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2016 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/Y.1369 (2013)/Amd.2 (04/2016) 1 Recomme
19、ndation ITU-T G.8275/Y.1369 Architecture and requirements for packet-based time and phase distribution 1) Clause 4, Abbreviations and acronyms In clause 2, add the following acronym in alphabetical order: HRM Hypothetical Reference Model 2) Clause 7.1, Packet-based time and phase distribution 2.1) F
20、ifth paragraph of clause 7.1 Modify the fifth paragraph of clause 7.1 as follows: The current version of this Recommendation describes an architecture for this case (full timing support to the protocol level), where all the intermediate nodes are telecom transparent clocks (T-TCs) or telecom boundar
21、y clocks (T-BCs) with physical layer frequency support. Transparent clocks are being studied and may be included in future versions of this Recommendation. 2.2) Eighth paragraph of clause 7.1 Modify clause 7.1 starting at paragraph 8 as follows: The time-transfer protocol operating between the nodes
22、 allows the same time to be recovered or corrected at all nodes participating in the timing protocol, subject to some degradation (). In some deployments, especially in the access part of the network, it may be convenient to provide timing support from the protocol via T-TC functions. One typical ex
23、ample is in case of microwave connections. NOTE The T-TCs are typically connected in tree architectures. Rings composed entirely of T-TCs can raise issues in terms of PTP packets loops. The general network topology for time/phase distribution from a packet master clock PRTC to a telecom time slave c
24、lock (T-TSC) is shown in Figure 1. The synchronization flow is from the master to slave, although the timing messages will flow in both directions. Individual nodes are telecom boundary clocks (T-BCs) or telecom transparent clocks (T-TCs) in the case of full support from the network. NOTE The follow
25、ing figure does not imply any hypothetical reference model (HRM). 2.3) Figure 1 Replace Figure 1 with the following figure: 2 Rec. ITU-T G.8275/Y.1369 (2013)/Amd.2 (04/2016) Figure 1 Time distribution to slave clocks 3) Clause 7.2, Time/phase protection aspects Add the following note to Figure 6: NO
26、TE In addition to being connected to a T-GM, a PRTC may be connected to a T-BC by the 1pps+ToD interface. This is useful for some applications such as achieving protection in ring network, see Appendix II. Add the following note to Figure 7: NOTE In addition to being connected to a T-GM, a PRTC may
27、be connected to a T-BC by the 1pps+ToD interface. This is useful for some applications such as achieving protection in ring network, see Appendix II. 4) New Appendix II Add the following as new Appendix II: Appendix II An example of PRTC switching by the BMCA in a ring network (This appendix does no
28、t form an integral part of this Recommendation.) Figure II.1 and Figure II.2 in the following show the application scenario. In the figures, the working PRTC has higher priority than the back-up PRTC. Normally, the working PRTC (i.e., PRTC-1) sends frequency via a 2048 kHz or 2048 kbit/s signal and
29、phase/time via a 1PPS + ToD signal to the T-BC that it is connected to. This T-BC is the GM, and all the network elements including the T-BC connected to the back-up PRTC (i.e., PRTC-2) track the phase/time of the working PRTC, as shown in Figure II.1. Rec. ITU-T G.8275/Y.1369 (2013)/Amd.2 (04/2016)
30、 3 Figure II.1 Normal state (T-BC connected to working PRTC is working as a GM) If, at some time, PRTC-1 is degraded (e.g., the GNSS signal is lost), or the connection between PRTC-1 and the T-BC it is connected to fails, PRTC-2 becomes the working PRTC. All the network elements will then track the
31、phase/time of PRTC-2, and the T-BC initially connected to PRTC-1 will no longer be the GM, as shown in Figure II.2. Figure II.2 Abnormal state (the working PRTC has failed) The above operation can be obtained using the BMCA by setting the clockClass of PRTC-1 and PRTC-2 to 6 when they are operating
32、normally (i.e., when they are traceable to a GNSS) and setting priority2 for PRTC-1 to be better (i.e., to have a smaller value) than priority2 for PRTC-1. Both PRTC-1 and PRTC-2 are attached to the respective T-BCs via virtual PTP ports (see b-ITU-T G.8275.1), and the respective PTP attributes, whi
33、ch include clockClass and priority2 are transferred via the 1PPS+ToD interfaces to the virtual PTP ports (see ITU-T G.8271). With these values for clockClass and priority2 (and with clockAccuracy and offsetScaledLogVariance of PRTC-1 and PRTC-2 the same) PRTC-1 will win the BMCA when it is operating
34、 normally because its clockClass will be the same or better than the clockClass of PRTC-2 and its priority2 will be better than the priority2 of PRTC-2. If PRTC-1 degrades, its clockClass will be worse than that of PRTC-2 4 Rec. ITU-T G.8275/Y.1369 (2013)/Amd.2 (04/2016) and PRTC-2 will win the BMCA
35、. If PRTC-1 is lost (i.e., the connection from PRTC-1 to the T-BC it is attached to is cut), there will be no input to the virtual PTP port and PRTC-2 will win the BMCA. 5 Bibliography Add the following as a new entry to the bibliography in the appropriate order: b-ITU-T G.8275.1 Recommendation ITU-
36、T G.8275.1/Y.1369.1 (2016), Precision time protocol telecom profile for phase/time synchronization with full timing support from the network. ITU-T Y-SERIES RECOMMENDATIONS GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS, INTERNET OF THINGS AND SMART CITIES
37、GLOBAL INFORMATION INFRASTRUCTURE General Y.100Y.199 Services, applications and middleware Y.200Y.299 Network aspects Y.300Y.399 Interfaces and protocols Y.400Y.499 Numbering, addressing and naming Y.500Y.599 Operation, administration and maintenance Y.600Y.699 Security Y.700Y.799 Performances Y.800
38、Y.899 INTERNET PROTOCOL ASPECTS General Y.1000Y.1099 Services and applications Y.1100Y.1199 Architecture, access, network capabilities and resource management Y.1200Y.1299 Transport Y.1300Y.1399 Interworking Y.1400Y.1499 Quality of service and network performance Y.1500Y.1599 Signalling Y.1600Y.1699
39、 Operation, administration and maintenance Y.1700Y.1799 Charging Y.1800Y.1899 IPTV over NGN Y.1900Y.1999 NEXT GENERATION NETWORKS Frameworks and functional architecture models Y.2000Y.2099 Quality of Service and performance Y.2100Y.2199 Service aspects: Service capabilities and service architecture
40、Y.2200Y.2249 Service aspects: Interoperability of services and networks in NGN Y.2250Y.2299 Enhancements to NGN Y.2300Y.2399 Network management Y.2400Y.2499 Network control architectures and protocols Y.2500Y.2599 Packet-based Networks Y.2600Y.2699 Security Y.2700Y.2799 Generalized mobility Y.2800Y.
41、2899 Carrier grade open environment Y.2900Y.2999 FUTURE NETWORKS Y.3000Y.3499 CLOUD COMPUTING Y.3500Y.3999 INTERNET OF THINGS AND SMART CITIES AND COMMUNITIES General Y.4000Y.4049 Definitions and terminologies Y.4050Y.4099 Requirements and use cases Y.4100Y.4249 Infrastructure, connectivity and netw
42、orks Y.4250Y.4399 Frameworks, architectures and protocols Y.4400Y.4549 Services, applications, computation and data processing Y.4550Y.4699 Management, control and performance Y.4700Y.4799 Identification and security Y.4800Y.4899 For further details, please refer to the list of ITU-T Recommendations
43、. Printed in Switzerland Geneva, 2016 SERIES OF ITU-T RECOMMENDATIONS Series A Organization of the work of ITU-T Series D General tariff principles Series E Overall network operation, telephone service, service operation and human factors Series F Non-telephone telecommunication services Series G Tr
44、ansmission systems and media, digital systems and networks Series H Audiovisual and multimedia systems Series I Integrated services digital network Series J Cable networks and transmission of television, sound programme and other multimedia signals Series K Protection against interference Series L E
45、nvironment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant Series M Telecommunication management, including TMN and network maintenance Series N Maintenance: international sound programme and television tra
46、nsmission circuits Series O Specifications of measuring equipment Series P Terminals and subjective and objective assessment methods Series Q Switching and signalling Series R Telegraph transmission Series S Telegraph services terminal equipment Series T Terminals for telematic services Series U Tel
47、egraph switching Series V Data communication over the telephone network Series X Data networks, open system communications and security Series Y Global information infrastructure, Internet protocol aspects and next-generation networks, Internet of Things and smart cities Series Z Languages and general software aspects for telecommunication systems
