1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T I.326TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2003) SERIES I: INTEGRATED SERVICES DIGITAL NETWORK Overall network aspects and functions Reference models Functional architecture of transport networks based on ATM ITU-T Recommendation I.326 ITU-T
2、 I-SERIES RECOMMENDATIONS INTEGRATED SERVICES DIGITAL NETWORK GENERAL STRUCTURE Terminology I.110I.119 Description of ISDNs I.120I.129 General modelling methods I.130I.139 Telecommunication network and service attributes I.140I.149 General description of asynchronous transfer mode I.150I.199 SERVICE
3、 CAPABILITIES Scope I.200I.209 General aspects of services in ISDN I.210I.219 Common aspects of services in the ISDN I.220I.229 Bearer services supported by an ISDN I.230I.239 Teleservices supported by an ISDN I.240I.249 Supplementary services in ISDN I.250I.299 OVERALL NETWORK ASPECTS AND FUNCTIONS
4、 Network functional principles I.310I.319 Reference models I.320I.329 Numbering, addressing and routing I.330I.339 Connection types I.340I.349 Performance objectives I.350I.359 Protocol layer requirements I.360I.369 General network requirements and functions I.370I.399 ISDN USER-NETWORK INTERFACES A
5、pplication of I-series Recommendations to ISDN user-network interfaces I.420I.429 Layer 1 Recommendations I.430I.439 Layer 2 Recommendations I.440I.449 Layer 3 Recommendations I.450I.459 Multiplexing, rate adaption and support of existing interfaces I.460I.469 Aspects of ISDN affecting terminal requ
6、irements I.470I.499 INTERNETWORK INTERFACES I.500I.599 MAINTENANCE PRINCIPLES I.600I.699 B-ISDN EQUIPMENT ASPECTS ATM equipment I.730I.739 Transport functions I.740I.749 Management of ATM equipment I.750I.759 Multiplexing aspects I.760I.769 For further details, please refer to the list of ITU-T Reco
7、mmendations. ITU-T Rec. I.326 (03/2003) i ITU-T Recommendation I.326 Functional architecture of transport networks based on ATM Summary This Recommendation describes the functional architecture of the ATM transport assembly using the transport functional architecture defined in ITU-T Rec. G.805. The
8、 ATM transport assembly consists of the VC layer network, the VC to VP adaptation, the VP layer network and the VP to Transmission path adaptation. The features described in the I-series Recommendations that are relevant to ATM transport networks are described in this Recommendation. Annex A describ
9、es the correspondence between the terms used in ITU-T Recs I.326 and I.311. Source ITU-T Recommendation I.326 was revised by ITU-T Study Group 15 (2001-2004) and approved under the WTSA Resolution 1 procedure on 16 March 2003. ii ITU-T Rec. I.326 (03/2003) FOREWORD The International Telecommunicatio
10、n 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, operating and tariff questions and issuing Recommendations on them with a view
11、 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 ITU-T Recommendati
12、ons 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 used for concisene
13、ss 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 the Recommendation i
14、s 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 of any party. INTELL
15、ECTUAL 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 Property Rights, whe
16、ther 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, implementors are c
17、autioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 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. I.326 (03/200
18、3) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Abbreviations 2 4 Transport functional architecture of ATM networks 3 4.1 General . 3 4.2 ATM layer networks. 4 4.3 Client/server associations . 5 4.4 Connection supervision 9 4.5 Survivability techniques . 9 Annex A Correspondence of vocabulary betwe
19、en ITU-T Recs I.311 and I.326 10 A.1 ATM network layering. 10 A.2 Topological components inside a layer network 10 A.3 Transport entities and transport functions 11 A.4 Reference points . 11 Appendix I Multipoint connection 11 I.1 Multipoint connection point (MPCP). 11 I.2 Representation of multipoi
20、nt connections 11 ITU-T Rec. I.326 (03/2003) 1 ITU-T Recommendation I.326 Functional architecture of transport networks based on ATM 1 Scope This Recommendation describes the ATM network as a transport network from the viewpoint of its information transfer capability. More specifically, the function
21、al and structural architecture of a transport network based on ATM are described using the generic definitions, symbols and abbreviations that are defined in ITU-T Rec. G.805. This Recommendation describes the functional architecture of the ATM transport network using the transport functional archit
22、ecture defined in ITU-T Rec. G.805. The ATM transport network consists of the VC layer network, the VC to VP adaptation, the VP layer network and the VP to Transmission path adaptation. The features described in the I-series Recommendations that are relevant to ATM transport networks are described i
23、n this Recommendation. Annex A describes the correspondence between the terms used in ITU-T Recs I.326 and I.311. 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
24、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 Recommendations and other references listed below. A li
25、st 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 Recommendation G.707/Y.1322 (2000), Network node interface for the synchronous digital hie
26、rarchy (SDH). ITU-T Recommendation G.709/Y.1331 (2003), Interfaces for the Optical Transport Network (OTN). ITU-T Recommendation G.804 (1998), ATM cell mapping into plesiochronous digital hierarchy (PDH). ITU-T Recommendation G.805 (2000), Generic functional architecture of transport networks. ITU-T
27、 Recommendation I.113 (1997), Vocabulary of terms for broadband aspects of ISDN. ITU-T Recommendation I.233 (1991), Frame mode bearer services. ITU-T Recommendation I.311 (1996), B-ISDN general network aspects. ITU-T Recommendation I.361 (1999), B-ISDN ATM layer specification. ITU-T Recommendation I
28、.363.1 (1996), B-ISDN ATM Adaptation Layer Specification: Type 1 AAL. ITU-T Recommendation I.363.2 (2000), B-ISDN ATM Adaptation Layer Specification: Type 2 AAL. ITU-T Recommendation I.363.3 (1996), B-ISDN ATM Adaptation Layer Specification: Type 3/4 AAL. ITU-T Recommendation I.363.5 (1996), B-ISDN
29、ATM Adaptation Layer Specification: Type 5 AAL. 2 ITU-T Rec. I.326 (03/2003) ITU-T Recommendation I.364 (1999), Support of broadband connectionless data service by the B-ISDN. ITU-T Recommendation I.432.2 (1999), B-ISDN user-network interface Physical layer specification: 155 520 kbit/s and 622 080
30、kbit/s operation. ITU-T Recommendation I.432.4 (1999), B-ISDN user-network interface Physical layer specification: 51 840 kbit/s operation. ITU-T Recommendation I.432.5 (1997), B-ISDN user-network interface Physical layer specification: 25 600 kbit/s operation. ITU-T Recommendation I.610 (1999), B-I
31、SDN operation and maintenance principles and functions. ITU-T Recommendation I.630 (1999), ATM protection switching. ITU-T Recommendation I.731 (2000), Types and general characteristics of ATM equipment. _ ITU-T Recommendation I.732 (2000), Functional characteristics of ATM equipment. 3 Abbreviation
32、s This Recommendation uses the following abbreviations: AAL ATM Adaptation Layer (see ITU-T Rec. I.363.x) AIS Alarm Indication Signal (see ITU-T Rec. I.610) AP Access Point (see ITU-T Rec. G.805) APS Automatic Protection Switching ATM Asynchronous Transfer Mode (see ITU-T Rec. I.150) BCDBS Broadband
33、 Connectionless Data Bearer Service (see ITU-T Rec. I.364) CLP Cell Loss Priority (see ITU-T Rec. I.361) CP Connection Point (see ITU-T Rec. G.805) EFCI Explicit Forward Congestion Indication (see ITU-T Rec. I.371) ET Extra Traffic F4 OAM Maintenance flow at the VP level (see ITU-T Rec. I.610) F5 OA
34、M Maintenance flow at the VC level (see ITU-T Rec. I.610) FMBS Frame Mode Bearer Service (see ITU-T Rec. I.233) GFC Generic Frame Control (see ITU-T Rec. I.361) HEC Header Error Control (see ITU-T Rec. I.432) MPCP Multipoint Connection Point (see 4.4.1.1) OAM Operation and maintenance (see ITU-T Rec
35、. I.610) OTN Optical Transport Network (see ITU-T Rec. G.872) PDH Plesiochronous Digital Hierarchy (see ITU-T Rec. G.804) PMD Physical Media Dependant Layer (see ITU-T Rec. I.432.x) SD Signal Degrade SDH Synchronous Digital Hierarchy (see ITU-T Rec. G.707) ITU-T Rec. I.326 (03/2003) 3 SF Signal Fail
36、 SNC Subnetwork connection (see ITU-T Rec. G.805) STM Synchronous Transfer Mode (see ITU-T Rec. I.113) TCP Termination Connection Point (see ITU-T Rec. G.805) TP Trail in the transmission path server layer network (see 4.3.2) TPT Transmission path trail termination (see “Trail Termination“ in ITU-T
37、Rec. G.805) TSD Trail Signal Degrade TSF Trail Signal Fail VC Virtual Channel (see ITU-T Rec. I.113) VCC Virtual Channel Connection (see ITU-T Rec. I.311) VCI Virtual Channel Identifier (see ITU-T Rec. I.113) VCLC Virtual Channel Link Connection (see “Link connection“ in ITU-T Rec. G.805) VCNC Virtu
38、al Channel Network Connection (see “Network Connection“ in ITU-T Rec. G.805) VCSC Virtual Channel Subnetwork Connection (see “Subnetwork Connection“ in ITU-T Rec. G.805) VCT Virtual Channel Trail Termination (see “Trail Termination“ in ITU-T Rec. G.805) VP Virtual Path (see ITU-T Rec. I.113) VPC Vir
39、tual Path Connection (see ITU-T Rec. I.311) VPG Virtual Path Group (see 4.6.1) VPI Virtual Path Identifier (see ITU-T Rec. I.113) VPLC Virtual Path Link Connection (see “Link connection“ in ITU-T Rec. G.805) VPNC Virtual Path Network Connection (see “Network Connection“ in ITU-T Rec. G.805) VPSC Vir
40、tual Path Subnetwork Connection (see “Subnetwork Connection“ in ITU-T Rec. G.805) VPT Virtual Path Trail Termination (see “Trail Termination“ in ITU-T Rec. G.805) 4 Transport functional architecture of ATM networks 4.1 General The functional architecture of ATM transport networks is described using
41、the generic rules defined in ITU-T Rec. G.805. The specific aspects regarding the characteristic information, client/server associations, the topology, the connection supervision and multipoint capabilities of ATM transport networks are provided in this Recommendation. This Recommendation uses the t
42、erminology and functional architecture and diagrammatic conventions defined in ITU-T Rec. G.805. In an ATM network two levels of multiplexing are used to provide routing flexibility for ATM cell streams. An ATM cell is 53 octets long consisting of a 5-octet header and a 48-octet information field. T
43、he VCI and VPI fields in the cell header are used to perform two levels of multiplexing. This is analogous to the use of time-slots and hierarchical multiplexing in STM networks. 4 ITU-T Rec. I.326 (03/2003) 4.2 ATM layer networks Two layer networks are defined in the ATM transport network architect
44、ure: Virtual Channel (VC) Layer Network; Virtual Path (VP) Layer Network. 4.2.1 Virtual channel layer network The VC layer network provides the transport of adapted information through a VC trail between access points. The adapted information is a non-continuous flow of 48 octets plus one bit (used
45、by the client adaptation process) of client data. The VC layer network characteristic information is a non-continuous of flow of adapted information and F5 OAM information (see ITU-T Rec. I.610). The VC layer network contains the following transport processing functions and transport entities (see F
46、igure 1): VC trail; VC trail termination source (VCT source): generates F5 end-to-end OAM cells; VC trail termination sink (VCT sink): terminates F5 end-to-end OAM cells; VC network connection (VCNC); VC link connection (VCLC); VC subnetwork connection (VCSC). I.326_F01VCTsourceVCTsinkVC trailVCNCAP
47、TCPVCSCCP CP CP CP CPVCLC VCSC VCLC VCSC VCLCAPTCPFigure 1/I.326 VC layer network example 4.2.1.1 VC trail termination The VC trail termination source accepts adapted information at its input, inserts F5 end-to-end OAM cells and presents the characteristic information of the VC layer network at its
48、output. The VC trail termination source can be used without binding its input to an adaptation function, e.g., for testing purposes. The VC trail termination sink accepts the characteristic information of the VC layer network at its input, removes the F5 end-to-end OAM cells and presents the adapted
49、 information at its output. The VC trail termination (VCT) consists of a co-located VC trail termination source and sink pair. 4.2.2 Virtual path layer network The VP layer network provides the transport of adapted information through a VP trail between access points. The adapted information is a non-continuous flow of VC layer network characteristic information plus the VCI and EFCI (Explicit Forward Congestion Indication) header fields. The VP layer network characteristic information is a non
