1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T M.2401TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (12/2003) SERIES M: TMN AND NETWORK MAINTENANCE: INTERNATIONAL TRANSMISSION SYSTEMS, TELEPHONE CIRCUITS, TELEGRAPHY, FACSIMILE AND LEASED CIRCUITS International transport network Error performance limi
2、ts and procedures for bringing-into-service and maintenance of multi-operator international paths and sections within an optical transport network ITU-T Recommendation M.2401 ITU-T M-SERIES RECOMMENDATIONS TMN AND NETWORK MAINTENANCE: INTERNATIONAL TRANSMISSION SYSTEMS, TELEPHONE CIRCUITS, TELEGRAPH
3、Y, FACSIMILE AND LEASED CIRCUITS Introduction and general principles of maintenance and maintenance organization M.10M.299 International transmission systems M.300M.559 International telephone circuits M.560M.759 Common channel signalling systems M.760M.799 International telegraph systems and photot
4、elegraph transmission M.800M.899 International leased group and supergroup links M.900M.999 International leased circuits M.1000M.1099 Mobile telecommunication systems and services M.1100M.1199 International public telephone network M.1200M.1299 International data transmission systems M.1300M.1399 D
5、esignations and information exchange M.1400M.1999 International transport network M.2000M.2999 Telecommunications management network M.3000M.3599 Integrated services digital networks M.3600M.3999 Common channel signalling systems M.4000M.4999 For further details, please refer to the list of ITU-T Re
6、commendations. ITU-T Rec. M.2401 (12/2003) i ITU-T Recommendation M.2401 Error performance limits and procedures for bringing-into-service and maintenance of multi-operator international paths and sections within an optical transport network Summary This Recommendation gives error performance object
7、ives, limits and procedures for bringing-into-service (BIS) and maintenance of multi-operator international ODUk Paths and OTUk Sections in an Optical Transport Network (OTN). Source ITU-T Recommendation M.2401 was approved by ITU-T Study Group 4 (2001-2004) under the ITU-T Recommendation A.8 proced
8、ure on 14 December 2003. Keywords Background block error, bringing-into-service, error detection code, error performance objectives, error performance parameters, forward error correction, in-service measurements, ODUk path monitoring, optical transport network, OTN maintenance, severely errored sec
9、ond. ii ITU-T Rec. M.2401 (12/2003) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical,
10、 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, in tu
11、rn, 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 IEC. NOT
12、E 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 ensure e
13、.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 does not s
14、uggest 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 Property Right. ITU takes no position concerning the e
15、vidence, 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 patents, whic
16、h may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2004 All rights reserved. No part of this publication may be reproduced, by any means wh
17、atsoever, without the prior written permission of ITU. ITU-T Rec. M.2401 (12/2003) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Terms and definitions . 1 4 Abbreviations 2 5 Transport entities in the OTN. 3 5.1 General introduction. 3 5.2 Bidirectional transport entities and uni-directional monitor
18、ing . 4 6 Performance monitoring capabilities in the OTN. 4 6.1 Optical impairments and digital error performance . 4 6.2 Monitored layer signals 5 6.3 ODUk and OTUk overhead 5 6.4 In-Service Monitoring and Out-of-Service Measurement 6 7 Error performance events and parameters 6 7.1 Severely Errored
19、 Seconds and Background Block Errors 6 7.2 FEC Corrected Errors. 7 8 Availability . 7 9 Network reference model . 7 10 Error performance objectives . 8 10.1 Error performance objectives for the HROP 8 10.2 Error performance objectives for the domains of a real path . 8 10.3 Error performance objecti
20、ves for the section . 8 11 Performance limits General considerations. 9 11.1 Relationship between performance limits and performance objectives. 9 11.2 Types of limits 9 12 Bringing-Into-Service procedures and limits 10 12.1 Calculation of the BIS limits 10 13 Performance levels and limits for maint
21、enance 11 13.1 Calculation of limits for maintenance 11 ITU-T Rec. M.2401 (12/2003) 1 ITU-T Recommendation M.2401 Error performance limits and procedures for bringing-into-service and maintenance of multi-operator international paths and sections within an optical transport network 1 Scope This Reco
22、mmendation gives error performance objectives, limits and procedures for bringing-into-service (BIS) and maintenance of multi-operator international ODUk paths and OTUk sections in an Optical Transport Network (OTN). Note that possible consequences for the BIS and maintenance following from the use
23、of an OTN as a server network for analog client signals is outside the scope of this Recommendation. 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 publicatio
24、n, the editions indicated were valid. All Recommendations and other references are subject to 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 cur
25、rently 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 status of a Recommendation. ITU-T Recommendation G.709/Y.1331 (2003), Interfaces for the Optical Transport Network (OTN). ITU-T Recommend
26、ation G.798 (2002), Characteristics of optical transport network hierarchy equipment functional blocks. ITU-T Recommendation G.874 (2001), Management aspects of the optical transport network element. ITU-T Recommendation G.7710/Y.1701 (2001), Common equipment management function requirements. ITU-T
27、Recommendation G.8201 (2003), Error performance parameters and objectives for multi-operator international paths within the Optical Transport Network (OTN). ITU-T Recommendation M.20 (1992), Maintenance philosophy for telecommunication networks. ITU-T Recommendation M.60 (1993), Maintenance terminol
28、ogy and definitions. ITU-T Recommendation M.2110 (2002), Bringing into service international multi-operator paths, sections and transmission systems. ITU-T Recommendation M.2120 (2002), International multi-operator paths, sections and transmission systems fault detection and localization procedures.
29、 3 Terms and definitions General terms and definitions related to maintenance are provided in ITU-T Recs M.20 and M.60. Terms and definitions related to OTN performance assessment are given in ITU-T Rec. G.8201. 2 ITU-T Rec. M.2401 (12/2003) 4 Abbreviations This Recommendation uses the following abb
30、reviations: 3R Reamplification, Reshaping and Retiming APO Allocated Performance Objective BBE Background Block Error BBER Background Block Error Ratio BDI Backward Defect Indication BEI Backward Error Indication BIP Bit Interleaved Parity BIS Bringing-Into-Service BISPO Bringing-Into-Service Perfor
31、mance Objective BOD Backbone Operator Domain DPL Degraded Performance Level DXC Digital Crossconnect EDC Error Detection Code EMF Equipment Management Function ES Errored Second ESR Errored Second Ratio FCE FEC Corrected Errors FEC Forward Error Correction HROP Hypothetical Reference Optical Path IO
32、D Inter-Operator Domain ISM In-Service Monitoring LOD Local Operator Domain LT Line Terminal OCADM Optical Add/Drop Multiplexer OCh Optical Channel OCXC Optical Crossconnect OD Operator Domains ODUk Optical Data Unit k, where k = 1, 2, 3 OG Operator Gateway OH Overhead OMS Optical Multiplex Section
33、OPUk Optical Payload Unit k, where k = 1, 2, 3 OS Optical Section OSM Out-of-Service Measurement OTN Optical Transport Network ITU-T Rec. M.2401 (12/2003) 3 OTUk Optical Transport Unit k, where k = 1, 2, 3 PO Performance Objective PRBS Pseudo-Random Binary Sequence ROD Regional Operator Domain SES S
34、everely Errored Second SESR Severely Errored Second Ratio SLA Service Level Agreement STM Synchronous Transport Module TP Test Period UPL Unacceptable Performance Level 5 Transport entities in the OTN 5.1 General introduction Figure 1 provides a simplified view of the OTN information structure hiera
35、rchy. The client signal, together with associated overhead, is mapped into the payload area of an Optical Payload Unit k (OPUk). The OPUk, together with its overhead, is mapped into the payload area of an Optical Data Unit k (ODUk). The ODUk, together with its overhead, is mapped into the payload ar
36、ea of an Optical Transport Unit k (OTUk). The OTUk is transported over the optical carrier network by inserting it in an Optical Channel (OCh). This picture does not show the various layers of the optical carrier network as their details are not relevant for the purpose of this Recommendation. M.240
37、1_F01Client signalPayloadOPUkODUkOTUkOptical carrier networkOHOHOH FEC OCh Payload unit OCh Data unit k OCh Transport unit kFigure 1/M.2401 OTN signal structure The ODUk and OTUk overhead (OH) bytes contain information used to check and to control the behaviour of the transport network. For the purp
38、ose of error performance monitoring, the Path Monitoring bytes in the ODUk OH and the Section Monitoring bytes in the OTUk OH are relevant: they contain amongst others Bit Interleaved Parity (BIP), Backward Error Indication (BEI) and Backward Defect Indication (BDI) information. Note that the OPUk O
39、H bytes do not contain error performance monitoring-related information. 4 ITU-T Rec. M.2401 (12/2003) The Forward Error Correction (FEC) bytes, which are part of the OTUk, serve the purpose of improving the error performance of the payload (in this case the ODUk together with its OH) under given op
40、tical transport conditions. Figure 2 shows how these transport entities may be used in an example OTN. In this example, the client signal transported between the terminating Digital Crossconnects (DXCs) is an STM-N. This STM-N is carried on the concatenation of an SDH section (OSn) and the end-to-en
41、d connection in the OTN, the ODUk. The ODUk is carried on a concatenation of OTUks, each delimited by a 3R regeneration point. Each OTUk is associated with an optical wavelength by means of the OCh. A number of OChs are multiplexed into an Optical Multiplex Section n (OMSn), which spans the distance
42、 between the line-terminating equipment: LTs, OCADMs, OCXCs. LTM.2401_F02OSnOTM-0OTM-nOTSnOTUkRSTM-NOptical Section Layer, level nOptical Transport Module 0Optical Transport Module nOptical Transport Section nOptical Transport Unit kRepeaterSynchronous Transport Module N3RDXCOCADMOchOCXCODUkOMSnOPS0
43、Reamplification, Reshaping and RetimingDigital CrossconnectOptical Add/Drop MultiplexerOptical ChannelOptical CrossconnectOptical Data Unit kOptical Multiplex Section nOptical Physical Section 0STM-NODUkOCh, OTUkOCh, OTUk OCh, OTUkOTSn OTSn OTSn OTSn OTSn OSnOPS0OMSn OMSn OMSnDXC 3R 3R3R3RRR OCADMOC
44、XCDXCClientClientOTM-0OTM-nSTM-NL TFigure 2/M.2401 Usage of transport entities in the OTN 5.2 Bidirectional transport entities and unidirectional monitoring ITU-T Rec. G.709/Y.1331 defines the ODUk and the OTUk as bidirectional transport entities. ITU-T Rec. G.8201 defines error performance objectiv
45、es for bidirectional ODUks. However, for the purposes of BIS and maintenance, both directions are treated as independent entities and all objectives set forth in this Recommendation shall be met by each direction independently of the condition of the other direction. Clause 8 provides further clarif
46、ication on this issue. 6 Performance monitoring capabilities in the OTN 6.1 Optical impairments and digital error performance While traversing an optical fibre or an optically transparent network element, an optical signal is subject to a number of physical phenomena which impair the quality of the
47、signal. Typical examples are attenuation, polarization mode dispersion, chromatic dispersion, four-wave mixing and various scattering phenomena. This Recommendation does not elaborate on the details of these phenomena and the mechanisms through which they might affect the quality of the transport se
48、rvices provided by the optical signal. From the perspective of a client, it is sufficient to recognize that such impact may exist. The way in which this impact may be perceived, detected and quantified depends on the nature of the client signal. As the scope of this Recommendation is limited to digi
49、tal ITU-T Rec. M.2401 (12/2003) 5 client signals as standardized in ITU-T Rec. G.709/Y.1331, it uses the digital error performance of the ODUk and OTUk layer signals as a means to assess the quality of the transport services provided by an OTN. 6.2 Monitored layer signals This Recommendation sets objectives and limits for the path (ODUk) and the section (OTUk). The rationale is: The ODUk is the end-to-end connection in the OTN. Monitoring is needed because its performance is the performance of the OTN as perceived by the client. The OTUk is the
