1、 International Telecommunication Union ITU-T G.872TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2012) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital networks Optical transport networks Architecture of optical transport networks Recommendation ITU-T G.872 ITU-T G
2、-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 INTERNATIONAL CARRIER TELEPHONE SYSTEM
3、S 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 OPTICAL SYSTEMS CHARACTERISTICS G
4、.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 capabilities and functions G.830G.839 SDH network characteristics G.840G.849 Management of tra
5、nsport network G.850G.859 SDH radio and satellite systems integration G.860G.869 Optical transport networks G.870G.879DIGITAL 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.6
6、000G.6999 DATA OVER TRANSPORT GENERIC ASPECTS G.7000G.7999 PACKET OVER TRANSPORT ASPECTS G.8000G.8999 ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.872 (10/2012) i Recommendation ITU-T G.872 Architecture of optical transport network
7、s Summary Recommendation ITU-T G.872 describes the functional architecture of optical transport networks using the modelling methodology described in Recommendations ITU-T G.800 and ITU-T G.805. The optical transport network (OTN) functionality is described from a network level viewpoint, taking int
8、o account an optical network layered structure, client characteristic information, client/server layer associations, networking topology, and layer network functionality providing optical signal transmission, multiplexing, routing, supervision, performance assessment and network survivability. The o
9、ptical portion of the network is described in terms of spectrum management entities and maintenance entities. History Edition Recommendation Approval Study Group 1.0 ITU-T G.872 1999-02-26 13 2.0 ITU-T G.872 2001-11-29 15 2.1 ITU-T G.872 (2001) Amd. 1 2003-12-14 15 2.2 ITU-T G.872 (2001) Cor. 1 2005
10、-01-13 15 2.3 ITU-T G.872 (2001) Amd. 2 2010-07-29 15 3.0 ITU-T G.872 2012-10-29 15 ii Rec. ITU-T G.872 (10/2012) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). T
11、he 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 World Telecommunication Stand
12、ardization 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 some areas of information
13、 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 recognized operating agency. Co
14、mpliance 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 words “shall“ or some other
15、 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 attention to the possibility that the practice or impleme
16、ntation 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 Recommendation development process.
17、As of the date of approval of this Recommendation, ITU had 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 are therefore strongly urged t
18、o consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2013 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.872 (10/2012) iii Table of Contents Page 1 Scope 1 2 References. 1 3 Term
19、s and definitions . 2 3.1 Terms defined elsewhere 2 3.2 Terms defined in this Recommendation . 3 4 Abbreviations and acronyms 3 5 Conventions 5 6 Functional architecture of optical transport networks 6 7 OTN digital layers 7 7.1 Optical channel data unit (ODU) layer network . 10 7.2 Optical channel
20、transport unit (OTU) layer network . 14 7.3 Client/server associations . 15 8 OTN optical entities 17 8.1 Optical channel (OCh) layer network . 19 8.2 Optical multiplex section (OMS) . 22 8.3 Optical transmission section (OTS) 23 8.4 Media entities . 25 8.5 Client/server associations . 27 9 OTN topo
21、logy . 29 9.1 Unidirectional and bidirectional connections . 29 9.2 Point-to-multipoint media channels . 29 10 OTN management . 30 10.1 Generic requirements 30 10.2 OTN network management requirements 31 10.3 Connection supervision techniques 34 10.4 Connection supervision applications 34 11 OTN sur
22、vivability techniques . 35 11.1 Protection techniques 35 11.2 Network restoration 35 12 Subdividing of the OTN . 35 12.1 Domains using the black link approach 36 Appendix I Examples of multi-domain OTN applications . 37 Appendix II Construction of optical channel connections 39 Appendix III An examp
23、le of the use of the black link approach 40 Appendix IV Relationship between Recommendations ITU-T G.872 and ITU-T G.798 42 Rec. ITU-T G.872 (10/2012) 1 Recommendation ITU-T G.872 Architecture of optical transport networks 1 Scope This Recommendation describes the functional architecture of optical
24、transport networks using the modelling methodology described in ITU-T G.800 and ITU-T G.805. The optical transport network (OTN) functionality is described from a network level viewpoint, taking into account an optical network layered structure, client characteristic information, client/server layer
25、 associations, networking topology, and layer network functionality providing optical signal transmission, multiplexing, routing, supervision, performance assessment and network survivability. The optical portion of the network is described in terms of spectrum management entities and maintenance en
26、tities. This Recommendation is restricted to the functional description of optical transport networks that support digital signals. The support of analogue or mixed digital/analogue signals is outside the scope of this Recommendation. It is recognized that the design of optical networks is subject t
27、o limitations imposed by the accumulation of degradations introduced by the number of network elements and their network topology. However, many of these degradations and the magnitude of their effects are associated with particular technological implementations of the architecture described in this
28、 Recommendation and are therefore subject to change as technology progresses. As such, the description of these effects 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, constit
29、ute 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 therefore encouraged to investigate the possibility of applying the most recent edition of the Reco
30、mmendations 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 stand-alone document, the status of a Recommendation. ITU-T G.694.1 Recommendation ITU-T G694.1 (20
31、12), Spectral grids for WDM applications: DWDM frequency grid. ITU-T G.698.1 Recommendation ITU-T G.698.1 (2009), Multichannel DWDM applications with single-channel optical interfaces. ITU-T G.698.2 Recommendation ITU-T G.698.2 (2009), Amplified multichannel dense wavelength division multiplexing ap
32、plications with single channel optical interfaces. ITU-T G.707 Recommendation ITU-T G.707/Y.1322 (2007), Network node interface for the synchronous digital hierarchy (SDH). ITU-T G.709 Recommendation ITU-T G.709/Y.1331 (2012), Interfaces for the optical transport network (OTN). ITU-T G.798 Recommend
33、ation ITU-T G.798 (2010), Characteristics of optical transport network hierarchy equipment functional blocks. ITU-T G.800 Recommendation ITU-T G.800 (2012), Unified functional architecture of transport networks. 2 Rec. ITU-T G.872 (10/2012) ITU-T G.805 Recommendation ITU-T G.805 (2000), Generic func
34、tional architecture of transport networks. ITU-T G.870 Recommendation ITU-T G.870/Y.1352 (2012), Terms and definitions for optical transport networks (OTN). ITU-T G.873.1 Recommendation ITU-T G.873.1 (2011), Optical Transport Network (OTN): Linear protection. ITU-T G.873.2 Recommendation ITU-T G.873
35、.2 (2012), ODUk shared ring protection. ITU-T G.7712 Recommendation ITU-T G.7712/Y.1703 (2010), Architecture and specification of data communication network. ITU-T G.8080 Recommendation ITU-T G.8080/Y.1304 (2012), Architecture for the automatically switched optical network. 3 Terms and definitions 3
36、.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 adaptation management ITU-T G.870: The set of processes for managing client layer network adaptation to/from the server layer network. 3.1.2 administrative domain ITU-T G.805: For the purposes of this Re
37、commendation an administrative domain represents the extent of resources which belong to a single player such as a network operator, a service provider or an end-user. Administrative domains of different players do not overlap amongst themselves. 3.1.3 central frequency ITU-T G.870: The nominal1mid-
38、point of the optical frequency range over which the digital information of a particular OCh-P is modulated. 3.1.4 connection supervision ITU-T G.805: The process of monitoring the integrity of a “connection“ or “tandem connection“ which is part of a “trail“. 3.1.5 connectivity supervision ITU-T G.87
39、0: The set of processes for monitoring the integrity of the routing of the connection between source and sink trail terminations. 3.1.6 continuity supervision ITU-T G.870: The set of processes for monitoring the integrity of the continuity of a trail. 3.1.7 effective frequency slot ITU-T G.870: The
40、effective frequency slot of a media channel is that part of the frequency slots of the filters along the media channel that is common to all of the filters frequency slots. It is described by its nominal central frequency and its slot width. 3.1.8 frequency slot ITU-T G.694.1: The frequency range al
41、located to a slot and unavailable to other slots within a flexible grid. A frequency slot is defined by its nominal central frequency and its slot width. Within this Recommendation a fixed grid device is described in terms of the frequency slots it would have associated with it, if it were a flexibl
42、e grid device. 3.1.9 inter-domain interface (IrDI) ITU-T G.870: A physical interface that represents the boundary between the administrative domains of different network operators. The characteristics are defined in ITU-T G.709. _ 1Nominal means the intended mid-point of the range. The actual mid-po
43、int may be slightly offset by impairments such as long term drift. Rec. ITU-T G.872 (10/2012) 3 3.1.10 intra-domain interface (IaDI) ITU-T G.870: A physical interface within the domain of a single network operator. The characteristics are defined in ITU-T G.709. 3.1.11 maintenance indication ITU-T G
44、.870: The set of processes for indicating defects in a connection which is part of a trail in downstream and upstream directions. 3.1.12 management communications ITU-T G.870: The set of processes providing communications for management purposes. 3.1.13 media element ITU-T G.870: A media element dir
45、ects the optical signal or affects the properties of an optical signal, it does not modify the properties of the information that has been modulated to produce the optical signal. 3.1.14 network media channel ITU-T G.870: A media channel that supports a single OCh-P network connection. 3.1.15 optica
46、l channel data unit (ODUk) ITU-T G.870: The ODUk is an information structure consisting of the information payload (OPUk) and ODUk-related overhead. See ITU-T G.709 for the current valid values of k. 3.1.16 optical channel payload unit (OPUk) ITU-T G.870: The OPUk is the information structure used t
47、o adapt client information for transport over an optical channel. It comprises client information together with any overhead needed to perform rate adaptation between the client signal rate and the OPUk payload rate, and other OPUk overheads supporting the client signal transport. See ITU-T G.709 fo
48、r the current valid values of k. 3.1.17 optical channel transport unit (OTUkV) ITU-T G.870: The OTUk is the information structure used for transport of an ODUk over an OCh trail. See ITU-T G.709 for the current valid values of k. 3.1.18 optical supervisory channel (OSC) ITU-T G.870: The OSC supports
49、 the transfer of the non-associated overhead information for the OCh trail, OMS_ME and the OTS_ME. 3.1.19 optical transport hierarchy (OTH) ITU-T G.870: The OTH is a hierarchical set of digital transport layers, standardized for the transport of suitably adapted payloads within the OTN. 3.1.20 optical transport network (OTN) ITU-T G.870: An optical transport network (OTN) is composed of a set of optical network elements connected by opt
