1、 International Telecommunication Union ITU-T G.8262/Y.1362TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 1(02/2012) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Packet over Transport aspects Quality and availability targets SERIES Y: GLOBAL INFORMATION INFRASTRUC
2、TURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS Internet protocol aspects Transport Timing characteristics of a synchronous Ethernet equipment slave clock Amendment 1 Recommendation ITU-T G.8262/Y.1362 (2010) Amendment 1 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIG
3、ITAL 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 CHARACTERISTICS OF I
4、NTERNATIONAL 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.799 DIGITAL NE
5、TWORKS 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 ASPECTS G.8000G.899
6、9 Ethernet over Transport aspects G.8000G.8099 MPLS over Transport aspects G.8100G.8199 Quality and availability targets G.8200G.8299Service Management G.8600G.8699 ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.8262/Y.1362 (2010)/Am
7、d.1 (02/2012) i Recommendation ITU-T G.8262/Y.1362 Timing characteristics of a synchronous Ethernet equipment slave clock Amendment 1 Summary Amendment 1 to Recommendation ITU-T G.8262/Y.1362 (2010) adds a new Appendix IV, “Considerations related to synchronous Ethernet over 1000BASE-T and 10GBASE-T
8、“. History Edition Recommendation Approval Study Group 1.0 ITU-T G.8262/Y.1362 2007-08-13 15 1.1 ITU-T G.8262/Y.1362 (2007) Amd. 1 2008-04-29 15 1.2 ITU-T G.8262/Y.1362 (2007) Amd.2 2010-01-13 15 2.0 ITU-T G.8262/Y.1362 2010-07-29 15 2.1 ITU-T G.8262/Y.1362 (2010) Amd. 1 2012-02-13 15 ii Rec. ITU-T
9、G.8262/Y.1362 (2010)/Amd.1 (02/2012) 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-T) is a permanent organ
10、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 years, establishes the top
11、ics 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 necessary standards are pre
12、pared 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. However, the Recommendation m
13、ay 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 equivalents are used to
14、express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual
15、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 had received notice of
16、 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/ITU-T/ipr/. ITU 2012 A
17、ll 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.8262/Y.1362 (2010)/Amd.1 (02/2012) 1 Recommendation ITU-T G.8262/Y.1362 Timing characteristics of a synchronous Ethernet equipment slave clock Amendme
18、nt 1 Add a new Appendix IV, as follows: Appendix IV Considerations related to synchronous Ethernet over 1000BASE-T and 10GBASE-T (This appendix does not form an integral part of this Recommendation) Synchronous Ethernet requires the relevant synchronization parameters of the network elements (e.g.,
19、link selected as candidate synchronization reference, priority) to be configured according to the network synchronization plan. The following discussion focuses on 1000BASE-T and 10GBASE-T, as for these interfaces the timing direction could become incompatible with the network synchronization plan d
20、ue to the configuration of the master-slave relationship as defined by IEEE 802.3. NOTE The following applies to unidirectional (from a synchronization viewpoint) interfaces. The application of similar rules to links in a ring where the timing chain might have to be reversed is for further study. Th
21、e following convention is used below: Clock master/slave: IEEE 802.3 master or slave state Sync master/slave: ITU-T G.8264 sync timing chain master or slave state In order to allow the proper setting of SyncE over 1000BASE-T and 10GBASE-T links, the Ethernet PHY could be configured either with a man
22、ual configuration or via auto-negotiation. If manual configuration is used, the operator must take care to correctly configure the clock master/slave setting of the PHY ports according to the network synchronization plan so that candidates for sync slaves are clock slaves and the sync master ports a
23、re clock masters. The use of manual configuration, if not properly done, may result in a failure condition and the consequent loss of the traffic connection to the equipment. As an example, if by mistake both ends are forced to be masters, the result is a configuration fault (see Table 40-5 1000BASE
24、-T MASTER-SLAVE configuration resolution table in IEEE 802.3). If auto-negotiation is used, the previous potential issues are prevented by the network element thus avoiding the result of a link not working. NOTE In this case, even if the PHY ports are not configured according to the network synchron
25、ization plan, the auto-negotiation may fail to get working network synchronization (with no indication of such timing discrepancy) but it will not jeopardize the possibility of getting working Ethernet traffic, and subsequent actions are possible in order to correct the PHY port setting. A possible
26、sequence of steps to be followed when auto-negotiation is used is described below. 2 Rec. ITU-T G.8262/Y.1362 (2010)/Amd.1 (02/2012) NOTE It is assumed that these synchronous Ethernet interfaces are configured in synchronous operation mode: 1. All 1000BASE-T and 10GBASE-T ports must allow auto-negot
27、iation. 2. Auto-negotiation is initiated: In the case of 1000BASE-T, all ports shall be configured with Bit 9.12 = 0 (auto-negotiation not forced). If a port is involved in the network synchronization plan, the port that should act as sync master must be configured with Bit 9.10 = 1 (Table 40-3 in I
28、EEE 802.3) and the port that should act as sync slave must be configured with Bit 9.10 = 0. If details on the network synchronization plan are not available, ports should be configured with Bit 9.10 = 1. The configuration is done as per Table 40-5 in IEEE 802.3 (“The device with the higher SEED valu
29、e is configured as MASTER, otherwise SLAVE“). When details on the network synchronization plan are made available, having ports with Bit 9.10 = 1 as the preferred default state allows the modification of Bit 9.10 on the sync slave side only, usually in the downstream data path (see item 4 below). NO
30、TE Having ports with bit 9.10 = 0 as the preferred default state requiring the modification of the Bit 9.10 on the sync master side only, would give a similar result. This Recommendation suggests a default configuration for easier interoperability. In the case of 10GBASE-T, all ports shall be config
31、ured with Bit U11= 0 (see Table 55-11 in IEEE 802.3). If a port is involved in the network synchronization plan, the port that should act as sync master must be configured with Bit U13 = 1 (multiport device, see Table 55-11 in IEEE 802.3) and the port that should act as sync slave must be configured
32、 with Bit U13 = 0 (single port device, see Table 55-11 in IEEE 802.3). If details on the network synchronization plan are not available, ports should be configured with Bit U13 = 1. When details on the network synchronization plan are made available, having ports with bit U13 =1 as the preferred def
33、ault state allows the modification of the Bit U13 on the sync slave side only, usually in the downstream data path (see item 4 below). NOTE Having ports with bit U13 = 0 as the preferred default state requiring the modification of the Bit U13 on the sync master side only, would give a similar result
34、. This Recommendation suggests a default configuration for easier interoperability. 3. The configuration of the network synchronization parameters in the node according to the network synchronization plan should be done and checked after the clock master/slave of the 1000BASE-T or 10GBASE-T ports ha
35、s been completed. At this point, the links in the nodes that are clock slave can be configured as sync candidate (if the network synchronization plan requires it). 4. If the network synchronization plan is available only after the clock master/slave procedure has been completed, and if a 1000BASE-T
36、or 10GBASE-T port is not the clock slave, but should be the sync slave candidate according to the network synchronization plan (“sync slave“), this port shall initiate a change clock direction (as part of the sync candidate configuration) by means of the tools defined in Table 40-3 (1000BASE-T) and
37、Table 55-11 (10GBASE-T) of IEEE 802.3. In particular, In the case of 1000BASE-T, for this port, Bit 9.10 = 0 In the case of 10GBASE-T for this port, Bit U13 = 0. NOTE 1 Any change in parameters for 802.3 auto-negotiation would force a reset of the interface, leading to link failure for a certain amo
38、unt of time (variable up to a few seconds). NOTE 2 When these steps are not properly followed (e.g., some of the nodes have been manually configured), a specific alarm might be required in order to notify the operator to take necessary actions. ITU-T Y-SERIES RECOMMENDATIONS GLOBAL INFORMATION INFRA
39、STRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS 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
40、 and maintenance Y.600Y.699 Security Y.700Y.799 Performances Y.800Y.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.1399Interworking Y.1400Y.1499 Quality of ser
41、vice and network performance Y.1500Y.1599 Signalling Y.1600Y.1699 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.219
42、9 Service aspects: Service capabilities and service architecture Y.2200Y.2249 Service aspects: Interoperability of services and networks in NGN Y.2250Y.2299 Numbering, naming and addressing Y.2300Y.2399 Network management Y.2400Y.2499 Network control architectures and protocols Y.2500Y.2599 Smart ub
43、iquitous networks Y.2600Y.2699 Security Y.2700Y.2799 Generalized mobility Y.2800Y.2899 Carrier grade open environment Y.2900Y.2999 Future networks Y.3000Y.3099 For further details, please refer to the list of ITU-T Recommendations. Printed in Switzerland Geneva, 2012 SERIES OF ITU-T RECOMMENDATIONS
44、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 Transmission systems and media, digital systems and networks Series H Au
45、diovisual 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 Construction, installation and protection of cables and other elements
46、of outside plant Series M Telecommunication management, including TMN and network maintenance Series N Maintenance: international sound programme and television transmission circuits Series O Specifications of measuring equipment Series P Terminals and subjective and objective assessment methods Ser
47、ies Q Switching and signalling Series R Telegraph transmission Series S Telegraph services terminal equipment Series T Terminals for telematic services Series U Telegraph 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 Series Z Languages and general software aspects for telecommunication systems
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