1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T G.826TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (12/2002) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital networks Quality and availability targets End-to-end error performance parameters and objectives for internationa
2、l, constant bit-rate digital paths and connections ITU-T Recommendation G.826 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 SY
3、STEMS G.200G.299 INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL 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 A
4、ND LINE TELEPHONY G.450G.499 TESTING EQUIPMENTS G.500G.599 TRANSMISSION MEDIA CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 General aspects G.800G.809 Design objectives for digital networks G.810G.819 Quality and availability targets G.820G.829 Network
5、 capabilities and functions G.830G.839 SDH network characteristics G.840G.849 Management of transport network G.850G.859 SDH radio and satellite systems integration G.860G.869 Optical transport networks G.870G.879 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 QUALITY OF SERVICE AND PERFORMANCE
6、 G.1000G.1999 TRANSMISSION MEDIA CHARACTERISTICS G.6000G.6999 DIGITAL TERMINAL EQUIPMENTS G.7000G.7999 DIGITAL NETWORKS G.8000G.8999 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. G.826 (12/2002) i ITU-T Recommendation G.826 End-to-end error performance parameters
7、 and objectives for international, constant bit-rate digital paths and connections Summary This Recommendation defines end-to-end error performance parameters and objectives for international digital paths which operate at or above the primary rate and for international digital connections which ope
8、rate below the primary rate of the digital hierarchy. The objectives given are independent of the physical network supporting the path or connection. For digital paths which operate at or above the primary rate, this Recommendation is based upon a block-based measurement concept using error detectio
9、n codes inherent to the path under test. This supports in-service measurements. For digital connections which operate below the primary rate of the digital hierarchy, this Recommendation is based upon bit error and bit error ratio measurements. This approach does not support in-service measurements.
10、 Annex A deals with the definition of availability of the path or connection. Annexes B, C and D give specific information concerning PDH, SDH and cell-based transmission paths. It is not required to apply this Recommendation to connections which operate below the primary rate using equipment design
11、ed prior to the adoption of this Recommendation in December 2002. This Recommendation deals with the performance of PDH paths, and of those SDH paths using equipment designed prior to the adoption of ITU-T Rec. G.828 in March 2000. ITU-T Rec. G.828 deals with the performance of SDH paths using equip
12、ment designed as of or after the adoption of ITU-T Rec. G.828 in March 2000. New Recommendation G.8201 deals with performance of ODUk paths of the OTN. Source ITU-T Recommendation G.826 was revised by ITU-T Study Group 13 (2001-2004) and approved under the WTSA Resolution 1 procedure on 14 December
13、2002. Keywords Background block error, background block error ratio, bit error, bit error ratio, block-based concept, digital connection, digital path, error detection codes, error performance objectives, error performance parameters, errored second, in-service measurements, severely errored second.
14、 ii ITU-T Rec. G.826 (12/2002) 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, oper
15、ating 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 turn, p
16、roduce 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. NOTE In
17、this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may invol
18、ve 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 Recommendation development process. As of the date of approval of this Recom
19、mendation, ITU had not received notice of intellectual property, protected by patents, which 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. I
20、TU 2003 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. G.826 (12/2002) iii CONTENTS Page 1 Scope 1 1.1 Application of this Recommendation. 1 1.2 Transport network layers 2 1.2.1 PDH and SDH transpor
21、t networks . 2 1.2.2 ATM connections . 2 1.3 Allocation of end-to-end performance . 3 2 References. 3 3 Abbreviations 4 4 Terms and definitions . 6 4.5 Error performance events for paths 6 4.6 Error performance events for connections . 7 4.7 Error performance parameters 7 5 The measurement of the bl
22、ock 7 5.1 In-service monitoring of blocks 7 5.2 Out-of-service measurements of blocks . 8 6 Performance assessment . 8 6.1 Implications for error performance measuring devices 8 6.2 Performance monitoring at the near end and far end of a path 8 7 Error performance objectives . 8 7.1 End-to-end objec
23、tives. 8 7.2 Apportionment of end-to-end objectives 10 7.2.1 Allocation to the national portion of the end-to-end path or connection . 10 7.2.2 Allocation to the international portion of the end-to-end path or connection. 11 Annex A Criteria for entry and exit for the unavailable state. 11 A.1 Crite
24、ria for a single direction 11 A.2 Criterion for a bidirectional path or connection . 12 A.3 Criterion for a unidirectional path or connection . 12 A.4 Consequences on error performance measurements 12 Annex B Relationship between PDH path performance monitoring and the block-based parameters. 13 B.1
25、 General . 13 B.1.1 Block size for monitoring PDH paths 13 B.1.2 Anomalies. 13 B.1.3 Defects 13 iv ITU-T Rec. G.826 (12/2002) Page B.2 Types of paths. 14 B.3 Estimation of the performance parameters. 14 B.4 In-service monitoring capabilities and criteria for declaration of the performance parameters
26、 . 15 B.5 Estimation of performance events at the far end of a path. 16 B.6 Differences between this Recommendation and ITU-T Rec. M.2100 concerning path performance . 16 B.6.1 General . 16 B.6.2 Allocation methodology . 16 Annex C Relationship between SDH path performance monitoring and the block-b
27、ased parameters. 17 C.1 General . 17 C.1.1 Converting BIP measurements into errored blocks 17 C.1.2 Block size for monitoring SDH paths 17 C.1.3 Anomalies. 17 C.1.4 Defects 17 C.1.5 Measurement of performance events using aggregate parity error counts. 18 C.2 Estimation of the performance parameters
28、. 19 C.3 Estimation of performance events at the far end of a path. 19 Annex D Relationship between cell-based network performance monitoring and the block-based parameters 19 D.1 General . 19 D.1.1 Block size for monitoring cell-based paths 19 D.1.2 Anomalies. 20 D.1.3 Defects 20 D.2 Types of paths
29、. 21 D.3 Estimation of the performance parameters. 21 D.4 Estimation of performance events at the far end of the path 21 Appendix I Flow chart illustrating for digital paths the recognition of anomalies, defects, errored blocks, ES and SES. 22 Appendix II Bit errors and block errors, merits and limi
30、tations . 23 Appendix III Applicability of this Recommendation to non-public networks . 24 ITU-T Rec. G.826 (12/2002) 1 ITU-T Recommendation G.826 End-to-end error performance parameters and objectives for international, constant bit-rate digital paths and connections 1 Scope This Recommendation spe
31、cifies end-to-end error performance events, parameters and objectives for: 1) digital paths operating at bit rates at or above the primary rate; and 2) N 64 kbit/s circuit-switched digital connection (1 N 24 or 31 respectively). This Recommendation also specifies allocations of the end-to-end perfor
32、mance objectives. 1.1 Application of this Recommendation This Recommendation is applicable to international, constant bit-rate digital paths which operate at or above the primary rate and to international N 64 kbit/s (1 N 24 or 31 respectively) digital connections. NOTE It is not required to apply t
33、his Recommendation to connections which operate below the primary rate using equipment designed prior to the adoption of this Recommendation in December 2002. Performance events and objectives for connections using equipment designed prior to this date are given in ITU-T Rec. G.821 14. The constant
34、bit-rate digital paths may be based on a Plesiochronous Digital Hierarchy, Synchronous Digital Hierarchy or some other transport network such as cell-based. This Recommendation is generic in that it defines the parameters and objectives for the paths and connections independent of the physical trans
35、port network. Compliance with the path performance specification of this Recommendation will, in most cases, also ensure that a client 64 kbit/s connection will meet its requirements. Therefore, this Recommendation and ITU-T Rec. G.828 24 are currently the only Recommendations required for designing
36、 the error performance of digital paths at or above the primary rate1. In accordance with the definition of a digital path, path end points may be located at users premises. Paths are used to support services such as circuit switched, packet switched and leased circuit services. The quality of such
37、services, as well as the performance of the network elements belonging to the service layer, is outside of the scope of this Recommendation. The performance objectives are applicable to a single direction of the path or connection. The values apply end-to-end over a 27 500 km Hypothetical Reference
38、Path or Connection (see Figure 3), which may include optical fibre, digital radio relay, metallic cable and satellite transmission systems. The performance of multiplex and cross-connect functions employing ATM techniques is not included in these values. The parameter definitions for digital paths w
39、hich operate at or above the primary rate are block-based, making in-service measurement convenient. In some cases, the network fabric is not able to provide the basic events necessary to directly obtain the performance parameters. In these cases, compliance with this Recommendation can be assessed
40、using out-of-service measurements or estimated by measures compatible with this Recommendation, such as those specified in _ 1This Recommendation deals with the performance of PDH paths, and of those SDH paths using equipment designed prior to the adoption of ITU-T Rec. G.828 in March 2000. ITU-T Re
41、c. G.828 deals with the performance of SDH paths using equipment designed as of or after the adoption of ITU-T Rec. G.828 in March 2000. New ITU-T Rec. G.8201 deals with the performance of ODUk paths of the OTN. 2 ITU-T Rec. G.826 (12/2002) Annexes B, C and D. The parameter definitions for digital c
42、onnections which operate below the primary rate of the digital hierarchy are not block-based; rather, they are based upon bit error and bit-error ratio measurements. 1.2 Transport network layers For paths, this Recommendation specifies the error performance in a given transport network layer. Two ca
43、ses have to be considered: 1.2.1 PDH and SDH transport networks Figure 1 gives the intended scope where ATM does not form part of the end-to-end path. It should be noted that end-to-end performance monitoring is only possible if the monitored blocks together with the accompanying overhead are transm
44、itted transparently to the path end points. G.826_F01Application of this RecommendationNetwork fabric, e.g., PDH, SDHABNOTE A and B are path end points located at physical interfaces, e.g. in accordance with ITU-T Rec. G.703 1.Figure 1/G.826 Application of this Recommendation for a non-ATM end-to-en
45、d transmission path 1.2.2 ATM connections Where the path forms the physical part of an ATM connection (see Figure 2), the overall end-to-end performance of the ATM connection is defined by ITU-T Rec. I.356 16. In this case, this Recommendation can be applied with an appropriate allocation to the per
46、formance between the path end points where the physical layer of the ATM protocol reference model (see ITU-T Rec. I.321 15) is terminated by ATM cross-connects or switches. ATM transmission paths in the physical layer correspond to a stream of cells mapped either into a cell-based format or into SDH
47、 or PDH-based frame structures. G.826_F02Under studyITU-T Rec. I.356AALATMPLATMPL PLAALATMPLG.826 allocated G.826 allocatedAAL ATM Adaptation LayerATM ATM LayerPL Physical LayerFigure 2/G.826 Architectural relationship between this Recommendation G.826 and ITU-T Rec. I.356 16 ITU-T Rec. G.826 (12/20
48、02) 3 1.3 Allocation of end-to-end performance Allocations of end-to-end performance of CBR paths and connections are derived using the rules laid out in 7.2 which are length- and complexity-based. Detailed allocations of G.826 performance to the individual components (lines, sections, multiplexers
49、and cross-connects, etc.) are outside the scope of this Recommendation, but when such allocations are performed, the national and international allocations as given in 7.2 shall be achieved. 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 publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this
