1、 International Telecommunication Union ITU-T G.800TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (02/2012) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital networks General aspects Unified functional architecture of transport networks Recommendation ITU-T G.800 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.809Design 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 tran
5、sport 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 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.800 (02/2012) i Recommendation ITU-T G.800 Unified functional architecture of transp
7、ort networks Summary Recommendation ITU-T G.800 describes a unified functional architecture for transport networks that use connection-oriented circuit switching (CO-CS), connection-oriented packet switching (CO-PS), and connectionless packet-switching (CL-PS) in a technology-independent way. Histor
8、y Edition Recommendation Approval Study Group 1.0 ITU-T G.800 2007-09-06 15 1.1 ITU-T G.800 (2007) Amd. 1 2009-03-09 15 1.2 ITU-T G.800 (2007) Amd. 2 2010-09-06 15 2.0 ITU-T G.800 2012-02-13 15 ii Rec. ITU-T G.800 (02/2012) FOREWORD The International Telecommunication Union (ITU) is the United Natio
9、ns specialized agency in the field of telecommunications, 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 o
10、n 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, produce Recommendations on these topics. The approval of
11、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 this Recommendation, the expression “Administration“ is
12、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.g., interoperability or applicability) and compliance with
13、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 suggest that compliance with the Recommendation is required
14、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 evidence, validity or applicability of claimed Intellectual
15、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, which may be required to implement this Recommendation. However
16、, 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 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior
17、 written permission of ITU. Rec. ITU-T G.800 (02/2012) iii Table of Contents Page 1 Scope 1 2 References. 1 3 Definitions 1 3.1 Terms imported from ITU-T G.805 . 2 3.2 Terms defined in this Recommendation . 4 4 Abbreviations and acronyms 5 5 Conventions 6 6 Functional architecture of transport netwo
18、rks 8 6.1 Topological components 9 6.2 Derived network constructs for topological viewpoints . 10 6.3 Transport entities and their properties 13 6.4 Transport information entities 16 6.5 Transport processing functions . 17 6.6 Reference points . 20 6.7 Topology . 20 6.8 Layer relationships . 23 6.9
19、Transport over composite links 26 7 Transparency and impairments . 27 7.1 Inter-layer information dependency. 28 8 Sublayers 29 8.1 Channel forwarding 29 8.2 Destination forwarding . 31 9 Transport network availability enhancement techniques . 33 9.1 Differentiated connection protection 33 9.2 Compo
20、site link protection 34 Annex A Fundamental concepts used in Recommendation ITU-T G.800 . 36 A.1 Axioms of the unified architecture . 36 A.2 Information . 36 A.3 Encoding and labelling . 38 A.4 Identity and identifiers 40 Annex B Definition and properties of a system 42 B.1 Introduction 42 B.2 Infor
21、mation systems . 44 B.3 Basic transfer function and telecommunications network 45 Annex C Communication . 49 C.1 Service configuration 49 C.2 Forwarding modes of a transport entity 50 iv Rec. ITU-T G.800 (02/2012) Page C.3 Monitoring of a transport entity . 50 Annex D Transport entity roles . 51 D.1
22、 Overview of transport entity roles 51 D.2 Roles of the transport entity within an operational domain . 51 D.3 Roles of the transport entity across multiple operational domains . 52 Appendix I Use of identifiers 53 I.1 Use of identifiers 53 Appendix II Relationships between architectural entities .
23、55 Appendix III Complexity and scalability of systems 56 III.1 Independence of subsystems 57 III.2 Independence within a lifecycle and between lifecycles 57 III.3 Transparency of telecommunications network services . 58 Appendix IV Access points in architecture and equipment Recommendations . 60 App
24、endix V Examples of roles of the transport entity 62 V.1 Examples of roles of the transport entity (TE) within an operational domain 62 V.2 Roles of TEs that span multiple operational domains . 63 Bibliography. 65 Rec. ITU-T G.800 (02/2012) 1 Recommendation ITU-T G.800 Unified functional architectur
25、e of transport networks 1 Scope A telecommunication network is a complex network which can be described in a number of different ways depending on the particular purpose of the description. This Recommendation describes the network as a transport network from the viewpoint of the information transfe
26、r capability. This Recommendation provides a set of constructs (definitions and diagrammatic symbols) and the semantics that can be used to describe such a viewpoint. A transport network transfers user information from a sender at one location to a receiver at another location. A transport network c
27、an also transfer various kinds of network control information such as signalling, and operations and maintenance information for the control functional group. This Recommendation describes the functional architecture of transport networks in a technology-independent way. The generic functional archi
28、tecture of transport networks provides the basis for a harmonized set of functional architecture Recommendations for specific layer network technologies, including those that use connection-oriented circuit switching (commonly referred to as CO-CS) or connection-oriented packet switching (commonly r
29、eferred to as CO-PS), and connectionless packet switching (commonly referred to as CL-PS), and a corresponding set of Recommendations for management, performance analysis, and equipment specifications. This Recommendation provides the definition of the architectural constructs that are required to d
30、escribe a transport network. The theoretical material that was used as the basis for these definitions is provided in Annex A (concepts), Annex B (properties of systems), and Annex C (properties of communications). 2 References The following ITU-T Recommendations and other references contain provisi
31、ons 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 therefore encouraged to investigate the possibili
32、ty 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 stand-alone document, the status of a Recommendat
33、ion. ITU-T G.805 Recommendation ITU-T G.805 (2000), Generic functional architecture of transport networks. ITU-T G.806 Recommendation ITU-T G.806 (2012), Characteristics of transport equipment Description methodology and generic functionality. ITU-T G.8080 Recommendation ITU-T G.8080/Y.1304 (2006),
34、Architecture for the automatically switched optical network. ITU-T X.200 Recommendation ITU-T X.200 (1994), Information technology Open Systems Interconnection Basic Reference Model: The basic model. 3 Definitions This Recommendation uses the following terms defined elsewhere: 2 Rec. ITU-T G.800 (02
35、/2012) 3.1 Terms imported from ITU-T G.805 This Recommendation uses the following terms defined in ITU-T G.805. The definitions are given here for the readers convenience. 3.1.1 access group: A group of co-located “trail termination“ functions that are connected to the same “subnetwork“ or “link“. 3
36、.1.2 access point (AP): A “reference point“ that consists of the pair of co-located “unidirectional access“ points, and therefore represents the binding between the trail termination and adaptation functions. 3.1.3 adaptation: A “transport processing function“ that consists of a co-located adaptatio
37、n source and sink pair. 3.1.4 adaptation sink: A “transport processing function“ which presents the client layer network characteristic information at its output by processing the information presented at its input by the server layer network trail. 3.1.5 adaptation source: A “transport processing f
38、unction“ which accepts client layer network characteristic information at its input and processes it to allow transfer over a trail (in the server layer network). 3.1.6 adapted information (AI): A signal which is transferred on “trails“. The specific formats will be defined in the technology specifi
39、c Recommendations. 3.1.7 architectural component: Any item used in this Recommendation to generically describe transport network functionality. 3.1.8 binding: A direct relationship between a “transport processing function“ or “transport entity“ and another “transport processing function“ or “transpo
40、rt entity“ which represents the static connectivity that cannot be directly modified by management action. 3.1.9 characteristic information (CI): A signal with a specific format, which is transferred on “network connections“. The specific formats will be defined in the technology specific Recommenda
41、tions. 3.1.10 client/server relationship: The association between layer networks that is performed by an “adaptation“ function to allow the link connection in the client layer network to be supported by a trail in the server layer network. 3.1.11 connection: A “transport entity“ which consists of an
42、 associated pair of “unidirectional connections“ capable of simultaneously transferring information in opposite directions between their respective inputs and outputs. 3.1.12 connection point (CP): A “reference point“ that consists of a pair of co-located “unidirectional connection points“ and there
43、fore represents the binding of two paired bidirectional “connections“. 3.1.13 layer network: A “topological component“ that represents the complete set of access groups of the same type which may be associated for the purpose of transferring information. 3.1.14 link: A “topological component“ which
44、describes a fixed relationship between a “subnetwork“ or “access group“ and another “subnetwork“ or “access group“. 3.1.15 matrix: It represents the limit to the recursive partitioning of a subnetwork. 3.1.16 matrix connection: A “transport entity“ that transfers information across a matrix, it is f
45、ormed by the association of “ports“ on the boundary of the matrix. 3.1.17 network: All of the entities (such as equipment, plant, facilities) which together provide communication services. Rec. ITU-T G.800 (02/2012) 3 3.1.18 network connection: A transport entity formed by a series of contiguous “li
46、nk connections“ and/or “subnetwork connections“ between “termination connection points“. 3.1.19 port: It consists of a pair of unidirectional ports. 3.1.20 reference point: An architectural component, which is formed by the binding between inputs and outputs of transport processing functions and/or
47、transport entities. 3.1.21 sublayer: A set of additional transport processing functions and reference points encapsulated within a layer network. It is created by decomposition of transport processing functions or reference points. 3.1.22 subnetwork: A topological component used to effect routing of
48、 a specific characteristic information. 3.1.23 subnetwork connection: A “transport entity“ that transfers information across a subnetwork, it is formed by the association of “ports“ on the boundary of the subnetwork. 3.1.24 topological component: An architectural component, used to describe the tran
49、sport network in terms of the topological relationships between sets of points within the same layer network. 3.1.25 trail: A “transport entity“ which consists of an associated pair of “unidirectional trails“ capable of simultaneously transferring information in opposite directions between their respective inputs and outputs. 3.1.26 trail termination: A “transport processing function“ that consists of a co-located trail termination source and sink pair. 3.1.27 trail termination sink: A “transport pro
