1、 International Telecommunication Union ITU-T G.8251TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (09/2010) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Packet over Transport aspects Quality and availability targets The control of jitter and wander within the optical trans
2、port network (OTN) Recommendation ITU-T G.8251 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 CHA
3、RACTERISTICS 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 AND LINE TELEPHONY G.450G.499 TR
4、ANSMISSION MEDIA AND 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 CHARAC
5、TERISTICS G.6000G.6999 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 Quality and availability targets G.8200G.8299Service Management G.8600G.8699 ACCESS NETWORKS G.9000
6、G.9999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.8251 (09/2010) i Recommendation ITU-T G.8251 The control of jitter and wander within the optical transport network (OTN) Summary Recommendation ITU-T G.8251 specifies the maximum network limits of jitter and
7、wander that shall not be exceeded and the minimum equipment tolerance to jitter and wander that shall be provided at any relevant interfaces which are based on the optical transport network (OTN). The requirements for the jitter and wander characteristics that are specified in this Recommendation mu
8、st be adhered to in order to ensure interoperability of equipment produced by different manufacturers and a satisfactory network performance. History Edition Recommendation Approval Study Group 1.0 ITU-T G.8251 2001-11-29 15 1.1 ITU-T G.8251 (2001) Cor. 1 2002-06-13 15 1.2 ITU-T G.8251 (2001) Amend.
9、 1 2002-06-13 15 1.3 ITU-T G.8251 (2001) Cor. 2 2008-05-22 15 1.4 ITU-T G.8251 (2001) Amend.2 2010-01-13 15 2.0 ITU-T G.8251 2010-09-22 15 ii Rec. ITU-T G.8251 (09/2010) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunicatio
10、ns, information and communication 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
11、 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, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid
12、 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 this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunicat
13、ion administration and a recognized 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 manda
14、tory 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 suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws a
15、ttention 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 evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or ot
16、hers 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, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represe
17、nt the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2011 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.8251 (09/2010
18、) iii Table of Contents Page 1 Scope 1 2 References. 2 3 Definitions 3 4 Abbreviations and acronyms 3 5 Network limits for the maximum output jitter and wander at an OTUk interface . 5 5.1 Network limits for jitter 5 5.2 Network limits for wander 6 6 Jitter and wander tolerance of network interfaces
19、 6 6.1 Jitter and wander tolerance of OTN interfaces . 6 6.2 Jitter and wander tolerance of client interfaces 11 Annex A Specification of the ODUk clock (ODC) 13 A.1 Scope 13 A.2 Applications 17 A.3 Frequency accuracy 17 A.4 Pull-in and pull-out ranges . 17 A.5 Noise generation . 18 A.6 Noise tolera
20、nce . 22 A.7 Jitter transfer . 22 A.8 Transient response 24 Appendix I Relationship between network interface jitter requirements and input jitter tolerance 26 I.1 Network interface jitter requirements . 26 I.2 Input jitter tolerance of network equipment . 27 Appendix II Effect of OTN on the distrib
21、ution of synchronization via STM-N and synchronous Ethernet clients 29 II.1 Introduction 29 II.2 Provisional synchronization reference chain 29 II.3 Synchronization network limit . 30 II.4 Variable channel memory . 31 II.5 Maximum buffer hysteresis 31 Appendix III Hypothetical reference model (HRM)
22、for 3R regenerator jitter accumulation . 33 Appendix IV 3R regenerator jitter accumulation analyses . 34 IV.1 Introduction 34 IV.2 Model 1 . 34 IV.3 Model 2 . 55 IV.4 Jitter generation of regenerators using parallel serial conversion 56 iv Rec. ITU-T G.8251 (09/2010) Page Appendix V Additional backg
23、round on demapper (ODCp) phase error and demapper wideband jitter generation requirements 58 V.1 Introduction 58 V.2 Demapper phase error . 58 V.3 Demapper wideband jitter generation due to gaps produced by fixed overhead in OTUk frame 60 Appendix VI OTN atomic functions . 63 VI.1 Introduction 63 Ap
24、pendix VII Hypothetical reference models (HRMs) for CBRx (SDH and synchronous Ethernet client) and ODUj/i payload jitter and short-term wander accumulation . 65 VII.1 Introduction 65 VII.2 OTN hypothetical reference models . 65 VII.3 Impact of the insertion of OTN islands in the ITU-T G.803 synchron
25、ization reference chain . 67 Appendix VIII CBRx and ODUj/i payload jitter and short-term wander accumulation analyses . 70 VIII.1 Introduction 70 VIII.2 Simulation model 70 VIII.3 Jitter and short-term wander simulation results 77 Bibliography. 113 Rec. ITU-T G.8251 (09/2010) v Introduction In an op
26、tical transport network (OTN), jitter and wander accumulate on transmission paths according to the jitter and wander generation and transfer characteristics of each respective equipment interconnected. This equipment may be, for example, 3R regenerators, client mappers, and client demappers/desynchr
27、onizers. An excessive amount of jitter and wander can adversely affect both digital (e.g., by generation of bit errors, frame slips and other abnormalities) and analogue baseband signals (e.g., by unwanted phase modulation of the transmitted signal). The consequences of such impairment will, in gene
28、ral, depend on the particular service that is being carried and the terminating or adaptation equipment involved. It is therefore necessary to set limits on the maximum magnitude of jitter and wander, and the corresponding minimum jitter and wander tolerance at network interfaces, in order to guaran
29、tee a proper quality of the transmitted signals and a proper design of the equipment. These network limits are independent of the particular service that is being carried. Rec. ITU-T G.8251 (09/2010) 1 Recommendation ITU-T G.8251 The control of jitter and wander within the optical transport network
30、(OTN) 1 Scope The scope of this Recommendation is to define the parameters and the relevant limits that satisfactorily control the amount of jitter and wander present at the OTN network-node interface (NNI). OTN network interfaces, to which this Recommendation is applicable, are defined in terms of
31、bit rates and frame structures in ITU-T G.709; the relevant equipment characteristics are described in ITU-T G.798 and the optical characteristics in ITU-T G.959.1 or ITU-T G.693. Additional information regarding the architecture of the OTN is found in ITU-T G.872. The network limits given in clause
32、 5, OTN interface tolerance specifications given in clause 6.1, and OTN equipment interface specifications given in Annex A apply at or refer to the OTUk interface. The relevant bit rates for these specifications are the OTUk bit rates. Note that some of the other requirements in this Recommendation
33、, e.g., the demapper clock (ODCp), asynchronous mapper clock (ODCa), and bit-synchronous mapper clock (ODCb) requirements in Annex A, apply to other interfaces and other bit rates (i.e., the demapper resides in the sink adaptation function between the ODUkP and CBR, ODUj/i or ODUkP/ODUj_A client, wh
34、ile the asynchronous and bit-synchronous mapper clocks reside in the source adaptation function between the ODUkP and client). In this Recommendation the term clock, when used in ODU clock (ODC), refers to a frequency source. Note that this Recommendation contains requirements for both non-OTN CBRx
35、clients mapped into ODUk and ODUj/i clients multiplexed into ODUk (k j). The OTN physical layer is not required to transport network synchronization. More precisely, neither the ODUk nor any layers below it are required to transport synchronization. Network synchronization distribution is a function
36、 of the client layer, e.g., SDH. ITU-T G.825 specifies the jitter and wander requirements for SDH clients, and any SDH signal (which must meet ITU-T G.825) is suitable for providing synchronization (see ITU-T G.803). SDH clients must meet ITU-T G.825 requirements for both asynchronous and bit-synchr
37、onous mappings. ITU-T G.8261 specifies the jitter and wander requirements of synchronous Ethernet for providing synchronization (see Annex D of ITU-T G.8261). Synchronous Ethernet clients must meet ITU-T G.8261 requirements for both GMP and bit-synchronous mappings. Jitter and wander requirements fo
38、r SDH networks are specified in ITU-T G.825. Jitter and wander requirements for PDH and synchronization networks are specified in ITU-T G.823, for networks based on the first level bit rate of 2048 kbit/s, and in ITU-T G.824 for networks based on the first-level bit rate of 1544 kbit/s. The jitter a
39、nd wander control philosophy is based on the need: to recommend a maximum network limit that should not be exceeded at any relevant OTN NNI; to recommend a consistent framework for the specification of individual digital equipment (i.e., jitter and wander transfer, tolerance and generation requireme
40、nts); to provide sufficient information and guidelines for organizations to measure and study jitter and wander accumulation in any network configuration. 2 Rec. ITU-T G.8251 (09/2010) Note that there may exist hybrid network element (NE) types that contain SDH, Ethernet, and/or OTN atomic functions
41、. For such hybrid NEs, it may not be possible to access the respective ports to make measurements to verify compliance with the requirements in this Recommendation. Measurements to verify compliance for hybrid NE types is outside the scope of this Recommendation. 2 References The following ITU-T Rec
42、ommendations 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 Recommendation are
43、therefore encouraged to investigate 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
44、stand-alone document, the status of a Recommendation. ITU-T G.693 Recommendation ITU-T G.693 (2006), Optical interfaces for intra-office systems. ITU-T G.707 Recommendation ITU-T G.707/Y.1322 (2000), Network node interface for the synchronous digital hierarchy (SDH). ITU-T G.709 Recommendation ITU-T
45、 G.709/Y.1331 (2009), Interfaces for the optical transport network (OTN), including its Amendment 1 (2010). ITU-T G.783 Recommendation ITU-T G.783 (2006), Characteristics of synchronous digital hierarchy (SDH) equipment functional blocks, including its amendments. ITU-T G.798 Recommendation ITU-T G.
46、798 (2010), Characteristics of optical transport network hierarchy equipment functional blocks. ITU-T G.803 Recommendation ITU-T G.803 (2000), Architecture of transport networks based on the synchronous digital hierarchy (SDH). ITU-T G.810 Recommendation ITU-T G.810 (1996), Definitions and terminolo
47、gy for synchronization networks. ITU-T G.811 Recommendation ITU-T G.811 (1997), Timing characteristics of primary reference clocks. ITU-T G.813 Recommendation ITU-T G.813 (2003), Timing characteristics of SDH equipment slave clocks (SEC). ITU-T G.823 Recommendation ITU-T G.823 (2000), The control of
48、 jitter and wander within digital networks which are based on the 2048 kbit/s hierarchy. ITU-T G.824 Recommendation ITU-T G.824 (2000), The control of jitter and wander within digital networks which are based on the 1544 kbit/s hierarchy. ITU-T G.825 Recommendation ITU-T G.825 (2000), The control of
49、 jitter and wander within digital networks which are based on the synchronous digital hierarchy (SDH), including its Amendment 1 (2008). ITU-T G.872 Recommendation ITU-T G.872 (2001), Architecture of optical transport networks. Rec. ITU-T G.8251 (09/2010) 3 ITU-T G.959.1 Recommendation ITU-T G.959.1 (2009), Optical transport network physical layer interfaces. ITU-T G.8261 Recommendation ITU-T G.8261/Y.1361 (2008), Timing and synchronization aspect
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