1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T Y.1712TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (01/2004) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT GENERATION NETWORKS Internet protocol aspects Operation, administration and maintenance OAM functionality for A
2、TM-MPLS interworking ITU-T Recommendation Y.1712 ITU-T Y-SERIES RECOMMENDATIONS GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT GENERATION NETWORKS GLOBAL INFORMATION INFRASTRUCTURE General Y.100Y.199 Services, applications and middleware Y.200Y.299 Network aspects Y.300Y.399 I
3、nterfaces and protocols Y.400Y.499 Numbering, addressing and naming Y.500Y.599 Operation, administration and maintenance Y.600Y.699 Security Y.700Y.799 Performances Y.800Y.899 INTERNET PROTOCOL ASPECTS General Y.1000Y.1099 Services and applications Y.1100Y.1199 Architecture, access, network capabili
4、ties and resource management Y.1200Y.1299 Transport Y.1300Y.1399 Interworking Y.1400Y.1499 Quality of service and network performance Y.1500Y.1599 Signalling Y.1600Y.1699 Operation, administration and maintenance Y.1700Y.1799 Charging Y.1800Y.1899 NEXT GENERATION NETWORKS Frameworks and functional a
5、rchitecture models Y.2000Y.2099 Quality of Service and performance Y.2100Y.2199 Service aspects: Service capabilities and service architecture Y.2200Y.2249 Service aspects: Interoperability of services and networks in NGN Y.2250Y.2299 Numbering, naming and addressing Y.2300Y.2399 Network management
6、Y.2400Y.2499 Network control architectures and protocols Y.2500Y.2599 Security Y.2700Y.2799 Generalized mobility Y.2800Y.2899 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. Y.1712 (01/2004) i ITU-T Recommendation Y.1712 OAM functionality for ATM-MPLS interworking
7、Summary This Recommendation describes OAM functionality for interworking between ATM and MPLS networks; specifically, procedures for interworking ATM OAM functionality (as described in ITU-T Rec. I.610) and MPLS OAM functionality (as described in ITU-T Rec. Y.1711) for fault management, notification
8、 and alarm suppression. Source ITU-T Recommendation Y.1712 was approved on 10 January 2004 by ITU-T Study Group 13 (2001-2004) under the ITU-T Recommendation A.8 procedure. Keywords ATM, interworking, MPLS, OAM ii ITU-T Rec. Y.1712 (01/2004) FOREWORD The International Telecommunication Union (ITU) i
9、s 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 to standardizi
10、ng 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 Recommendations is covered
11、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 conciseness to indicate
12、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 is achieved when
13、 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. INTELLECTUAL PROPERTY
14、 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, whether asserted b
15、y 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 cautioned that t
16、his may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2004 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. Y.1712 (01/2004) iii CONTENT
17、S Page 1 Scope 1 2 References. 1 3 Definitions and terminology. 1 4 Abbreviations 1 5 ATM-MPLS network interworking management model (overview). 2 6 Network interworking management functional model. 2 7 Network interworking defect, availability and performance considerations 5 8 Network interworking
18、: procedures at the egress IWF 5 9 Layer network interworking management reference model. 6 9.1 Overview 6 9.2 Layer network interworking in the ITU-T Rec. G.805 context 6 10 Layer network interworking defect, availability and performance considerations 7 11 Layer network interworking procedures at
19、an IWF 7 12 Security considerations. 8 Annex A Modifications to Y.1711 codepoints . 9 A.1 Additional Y.1711 Defect Type codepoints. 9 A.2 Modification to existing Y.1711 Defect Type codepoints . 9 Appendix I ATM-MPLS network interworking fault scenarios. 9 I.1 Automatic fault detection . 10 I.2 Faul
20、t indication. 10 Appendix II Layer network interworking fault scenarios. 15 II.1 Fault detection/notification/availability 15 II.2 LSP1-ME failure (fault location 1). 16 II.3 LSP2-ME failure (fault location 2). 17 II.4 LSP1-ME and LSP2-ME failure (fault locations 1 and 2) . 17 II.5 Fault in the IWF-
21、NE (fault location 3). 18 II.6 Fault in the ATM ME (fault location 4) . 18 ITU-T Rec. Y.1712 (01/2004) 1 ITU-T Recommendation Y.1712 OAM functionality for ATM-MPLS interworking 1 Scope This Recommendation addresses the interworking of ATM (I.610) and MPLS (Y.1711) OAM functionality in two scenarios:
22、 The first is network interworking, whereby ATM is transported (as the client layer) by MPLS (as the server layer) as defined in ITU-T Rec. Y.1411 or similar Recommendations. The second is layer network interworking 5, whereby the traffics data-plane for a p2p path is constructed of concatenated ATM
23、 and MPLS data-plane partitions. Defect states and consequent actions resulting from interworking of payload adaptation between ATM and MPLS is for further study (an example would be MTU or sequencing problems). 2 References The following ITU-T Recommendations and other references contain provisions
24、 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 possibility
25、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 Recommendation
26、. 1 ITU-T Recommendation Y.1711 (2004), Operation and maintenance mechanism for MPLS networks. 2 ITU-T Recommendation I.610 (1999), B-ISDN operation and maintenance principles and functions. 3 ITU-T Recommendation Y.1411 (2003), ATM-MPLS network interworking Cell mode user plane interworking. 4 ITU-
27、T Recommendation I.732 (2000), Functional characteristics of ATM equipment. 5 ITU-T Recommendation G.805 (2000), Generic functional architecture of transport networks. 6 ITU-T Recommendation I.357 (2000), B-ISDN semi-permanent connection availability. 7 IETF RFC 3031 (2001), Multiprotocol Label Swit
28、ching Architecture. 3 Definitions and terminology This Recommendation uses definitions and terminology from ITU-T Recs G.805, I.610, I.732, Y.1411 and Y.1711. 4 Abbreviations This Recommendation uses the following abbreviations: AIS Alarm Indication Signal ATM Asynchronous Transfer Mode BDI Backward
29、 Defect Indication 2 ITU-T Rec. Y.1712 (01/2004) CC Continuity Check CP Connection Point CV Connectivity Verification e-t-e end-to-end FDI Forward Defect Indication LC Link Connection LMI Layer Management Interface LSH Label Switch Hop LSP Label Switch Path ME Maintenance Entity MPLS Multi-Protocol
30、Label Switching NE Network Element NS Native Service RDI Remote Defect Indication TP Transmission Path VCC Virtual Channel Connection VCLC Virtual Channel Link Connection VPC Virtual Path Connection VPLC Virtual Path Link Connection 5 ATM-MPLS network interworking management model (overview) The ATM
31、-MPLS interworking function is composed of two management planes: the ATM management plane and the MPLS management plane. This Recommendation focuses on OAM information that has to be communicated between the two network data-planes without making any attempt to specify the mechanism for interaction
32、 between the two management planes. There are two classes of maintenance entities (MEs) in the case of ATM-MPLS network interworking: ATM and MPLS MEs (for example, a VPC/VCC in case of ATM, and an LSP in case of MPLS); Network interworking MEs (NI-MEs), which refer to the portion of the ATM ME that
33、 is interworked between the IWF ATM connection points. Note that an MPLS trail here is proving a link connection in the ATM layer network. This is a G.805 client/server relationship. It is useful to note that between other ATM nodes (in either of the end partitions) there will be trails of other (fo
34、r example) L1 CO-CS technology providing the link connections between the ATM nodes. The same is expected to be true for the link connections between the MPLS nodes. These relationships are also examples of network interworking. For layer network interworking, there is only one class of ME: the ATM
35、and MPLS maintenance entities. This is a G.805 layer network interworking relationship in which both entities have common semantics and simply require translation of the trail overhead at the interworking point. The link connections in either the ATM or MPLS layer networks can be provided by CO-CS s
36、erver trails as in the previous case (and where the relationship here is networking-interworking). 6 Network interworking management functional model Figure 6-1 shows the ATM-MPLS network interworking management reference model. ITU-T Rec. Y.1712 (01/2004) 3 MPLSIWF2EndSystem 1End ATM Network 1LSP1-
37、MEATM MEAT M1 -M ENetwork interworking MEMPLSAT MIWF1AT MLSP1-srcLSP2-sinkATM1-src/sinkLSP2-MECore MPLS networkEndSystem 2End ATM Network 2LSP1-LSP2-srcsinkATM2-src/sinkAT M2 -M EFigure 6-1/Y.1712 ATM-MPLS network interworking management reference model The key components of the model are: ATM ME: t
38、he ATM VCC or VPC transported between the ATM layer network trail termination points. End Systems 1 and 2: the ATM layer trail partitions that have a trail termination point at the end system and a connection point at the IWF. IWF1, IWF2: interworking functions that use procedures defined in ITU-T R
39、ec. Y.1411 to encapsulate/decapsulate ATM for transport over MPLS. LSP1-ME, LSP2-ME: the pair of unidirectional interworking LSPs that together provide bidirectional server layer transport for the ATM client link connection between IWF1 and IWF2. Network interworking ME: the portion of the ATM ME th
40、at exists between the ATM connection points at IWF1 and IWF2. ATM1-ME, ATM2-ME: elements of the ATM ME that are exclusive of the network interworking ME. The ATM layer trail partitions that have a trail termination point at the end system and a connection point at the IWF. This model assumes that th
41、e ATM ME is most usefully partitioned into a minimum of three ATM OAM segments. One or more ATM OAM segments exist between end system 1 and the IWF1 CP. One OAM segment is delineated by the connection points (CPs) co-located with IWF1 and IWF2. One or more ATM OAM segments exist between the IWF2 CP
42、and end system 2. This model may be mapped onto the I.610 reference model. In the network-interworking case, the MPLS MEs are interposed as a new level between the F3 and F4 OAM levels as illustrated in Figure 6-2. As such, the strict Fx OAM flow numbering relationships should not be taken too liter
43、ally. The only issue that is relevant is that a link connection in a given client layer network is provided by a trail in a server layer network, and that the OAM flows in each client/server layer network are independent. The VPLC/VCLC transported by the LSP1/2-MEs corresponds to the network interwo
44、rking ME. 4 ITU-T Rec. Y.1712 (01/2004) Virtual path network connection VCLCVCLCVCLCVPLCVPLCVPLCLabel switched path LSHLSHLSH(as per Figure 3/I.610)IWFIWFLSP2-MEVirtual channel network connectionF4 Virtualpath levelInterworking LSPTransport LSP(shown asbidirectional for simplicity)F3 Transmissionpat
45、h level.LSP1-MEF5 VirtualchannellevelPhysicallayerMPLSlayerATMlayer(IWF-ME)Figure 6-2/Y.1712 OAM hierarchy: I.610 view It is also possible to illustrate the network interworking scenario using G.805 as in Figure 6-3: ATM client layerLCMPLS server layerTrailFigure 6-3/Y.1712 Network interworking of A
46、TM over MPLS: G.805 context ITU-T Rec. Y.1712 (01/2004) 5 7 Network interworking defect, availability and performance considerations Network interworking of client/server OAM fault management relationships are possible when the server layer trail termination has knowledge of the client layer mainten
47、ance entities such that suitable entry to and exit from fault notification states can be performed. Based on ITU-T Recs I.610 and Y.1711, this is possible for Y.1411 3 one-to-one mode or for N-to-one mode when the egress IWF has knowledge of the client VPCs and VCCs transported by the interworking L
48、SP. The MPLS network in this scenario is invisible to the ATM end-user, as indeed it should be in any client/server layer network relationship. Therefore, the availability and performance of the IWF is perceived based on the availability of the end-end ATM trail (i.e., compliance to ITU-T Recs I.610
49、 and I.357). However, the end-to-end ATM trail availability and performance is dependent on the availability and performance of the MPLS network and is inherited from the constituent lower layers via ATM-MPLS interworking mechanisms. The same is true with respect to QoS metric collection. Since any MPLS layer (or lower CO-CS layer) defects will appear as ATM layer defects, it is vital to be able to suppress alarms and perform fault notification in all the layer networks above the one in which the defect ori
