1、 International Telecommunication Union ITU-T Series YTELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Supplement 4(01/2008) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS ITU-T Y.1300 series Supplement on transport requirements for T-MPLS OAM and c
2、onsiderations for the application of IETF MPLS technology ITU-T Y-series Recommendations Supplement 4 ITU-T Y-SERIES RECOMMENDATIONS GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS GLOBAL INFORMATION INFRASTRUCTURE General Y.100Y.199 Services, applications a
3、nd middleware Y.200Y.299 Network aspects Y.300Y.399 Interfaces 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 application
4、s Y.1100Y.1199 Architecture, access, network capabilities 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
5、 NEXT GENERATION NETWORKS Frameworks and functional architecture 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, n
6、aming and addressing Y.2300Y.2399 Network management 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. Y series Supplement 4 (01/2008) i Supplement 4 to
7、 ITU-T Y-series Recommendations ITU-T Y.1300 series Supplement on transport requirements for T-MPLS OAM and considerations for the application of IETF MPLS technology Summary This Supplement provides the requirements for the operation, administration and maintenance (OAM) functionality in T-MPLS lay
8、er networks. This Supplement is designed primarily to support point-to-point and point-to-multipoint T-MPLS connections. It is noted that this Supplement does not address the administration aspects of OAM. Source Supplement 4 to ITU-T Y-series Recommendations was agreed on 25 January 2008 by ITU-T S
9、tudy Group 13 (2005-2008). ii Y series Supplement 4 (01/2008) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU
10、-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 Standardization Assembly (WTSA), which meets every four y
11、ears, 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 technology which fall within ITU-Ts purview, the ne
12、cessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this publication, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this publication is voluntary. However, t
13、he publication may contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and compliance with the publication 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 a
14、re used to express requirements. The use of such words does not suggest that compliance with the publication is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this publication may involve the use of a claimed Intellec
15、tual 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 publication development process. As of the date of approval of this publication, ITU had not received notice
16、 of intellectual property, protected by patents, which may be required to implement this publication. However, 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 2008 A
17、ll rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Y series Supplement 4 (01/2008) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 2 4 Abbreviations and acronyms 2 5 Conventions 3 6 Reference networks 3 6
18、.1 Point-to-point T-MPLS connections 3 6.2 Point-to-multipoint T-MPLS connections 5 7 Motivation for OAM functionalities for T-MPLS-based networks 6 8 General requirements for T-MPLS layer OAM functions 7 9 Requirements for T-MPLS maintenance entities . 9 10 Required OAM functions . 10 10.1 Bidirect
19、ional point-to-point T-MPLS connections. 10 10.2 Unidirectional T-MPLS connections 10 11 Security aspects 11 Y series Supplement 4 (01/2008) 1 Supplement 4 to ITU-T Y-series Recommendations ITU-T Y.1300 series Supplement on transport requirements for T-MPLS OAM and considerations for the application
20、 of IETF MPLS technology 1 Scope This Supplement provides the requirements for the operation, administration and maintenance (OAM) functionality in T-MPLS layer networks from the perspective of transport networks and provides considerations for the application of IETF MPLS technology. These requirem
21、ents may be met by one or more toolsets, the definition or selection of these toolsets is outside the scope of this Supplement. This Supplement is designed to support point-to-point and point-to-multipoint T-MPLS connections. This requirements specification does not pre-judge whether a new OAM solut
22、ion is required for T-MPLS or whether an existing OAM solution could meet them. Since MPLS and T-MPLS are not necessarily disjoint networks, requirements to support the interoperability between T-MPLS OAM and OAMs and IETF MPLS technologies (e.g., MPLS, PWE3, L2VPN) need to be provided. Adding these
23、 requirements may result in some additions or modifications of the transport requirements identified in this Supplement. The requirements for IETF MPLS and OAM interoperability will follow the MPLS/GMPLS change process outlined in IETF RFC 4929. It is noted that this Supplement does not address the
24、administration aspects of OAM. 2 References 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 (2006), Characteristics of transport equipment Description methodology and generic functionality. ITU-T G.809 Recom
25、mendation ITU-T G.809 (2003), Functional architecture of connectionless layer networks. ITU-T G.7041 Recommendation ITU-T G.7041/Y.1303 (2005), Generic framing procedure (GFP). ITU-T G.7710 Recommendation ITU-T G.7710/Y.1701 (2007), Common equipment management function requirements. ITU-T G.8010 Rec
26、ommendation ITU-T G.8010/Y.1306 (2004), Architecture of Ethernet layer networks. ITU-T G.8110 Recommendation ITU-T G.8110/Y.1370 (2005), MPLS layer network architecture. ITU-T G.8110.1 Recommendation ITU-T G.8110.1/Y.1370.1 (2006), Architecture of Transport MPLS (T-MPLS) layer network. ITU-T M.3400
27、Recommendation ITU-T M.3400 (2000), TMN management functions. ITU-T Y.1541 Recommendation ITU-T Y.1541 (2006), Network performance objectives for IP-based services. ITU-T Y.1731 Recommendation ITU-T Y.1731 (2006), OAM functions and mechanisms for Ethernet based networks. 2 Y series Supplement 4 (01/
28、2008) IEEE 802.1ag IEEE 802.1ag-2007, IEEE Standard for Information technology Telecommunications and information exchange between systems Local and metropolitan area networks Virtual Bridged Local Area Networks Amendment 5: Connectivity Fault Management. IETF BCP 61 IETF Best Current Practice 61 (2
29、002), Strong Security Requirements for Internet Engineering Task Force Standard Protocols. IETF RFC 4929 IETF RFC 4929 (2007), Change Process for Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) Protocols and Procedures. 3 Definitions This Supplement uses the following terms defined
30、 elsewhere: 3.1 access point (AP): See ITU-T G.805. 3.2 anomaly: See ITU-T G.806. 3.3 client/server layer: See ITU-T G.806. 3.4 connection point (CP): See ITU-T G.805. 3.5 connection: See ITU-T G.805. 3.6 defect: See ITU-T G.806. 3.7 failure: See ITU-T G.806. 3.8 link connection: See ITU-T G.805. 3.
31、9 subnetwork connection (SNC): See ITU-T G.805. 3.10 termination connection point (TCP): See ITU-T G.806. 3.11 trail termination function (TT): See ITU-T G.806. 3.12 trail: See ITU-T G.805. 4 Abbreviations and acronyms This Supplement uses the following abbreviations and acronyms: AP Access Point AI
32、S Alarm Indication Signal CC Continuity and Connectivity Check CP Connection Point CSF Client Signal Fail ETY Ethernet Physical layer network FCAPS Fault, Configuration, Accounting, Performance and Security FP Flow point GMPLS Generalized Multi-Protocol Label Switching L2VPN Layer 2 Virtual Private
33、Network LC Link Connection Y series Supplement 4 (01/2008) 3 MCC Maintenance Communication Channel ME Maintenance Entity MEP Maintenance Entity Point MIP Maintenance Intermediate Point MPLS Multi-Protocol Label Switching OAM Operation, Administration and Maintenance PW Pseudo Wire PWE3 Pseudo-Wire E
34、mulation Edge-to-Edge SLA Service Level Agreement TCP Termination Connection Point TFP Termination Flow Point TM Transport Multi-Protocol Label Switching layer network T-MPLS Transport Multi-Protocol Label Switching UNI User Network Interface 5 Conventions None. 6 Reference networks This Supplement
35、specifies the requirements for OAM functions that are applied to point-to-point and point-to-multipoint T-MPLS connections. 6.1 Point-to-point T-MPLS connections Figure 1 provides a layered network perspective of a point-to-point connection according to the architecture defined in ITU-T G.8110.1. In
36、 this example, network elements A and E, which are placed in customer premises, can be associated with a client-layer CP, TCP, FP or TFP. Between the network elements B and D, which are placed at the edges of the providers network, the client-layer link connection or link flow is transported by a T-
37、MPLS network connection. This example is aligned with the different PW functional models described in Appendix I of ITU-T G.8110.1. Note that T-MPLS link connections are supported by different server layer technologies, S and Z. S and Z could be any server layer (including also the case of a T-MPLS
38、server layer network instance). Also note that although ETY is used for the server layer from A to B and from D to E in this example, it does not preclude the use of other server layers for these portions. This flexibility applies to all the examples in this Supplement. 4 Y series Supplement 4 (01/2
39、008) Figure 1 Example of point-to-point T-MPLS connection reference model Figure 2 shows the functional model of the hand-off portion between two providers. A and B denote the network elements placed at the boundary. It should be noted that the server layer between the hand-off points could be any s
40、erver layer, although ETY is used in this example. Figure 2 Example of hand-off point reference model The view of the reference models in terms of layer networks and the relationships can be simplified by considering only the connections present in the T-MPLS layer network (single layer network view
41、). This is illustrated in Figure 3. Y series Supplement 4 (01/2008) 5 Figure 3 Example of point-to-point connection reference models in the T-MPLS layer network (different server layer technologies) 6.2 Point-to-multipoint T-MPLS connections Figure 4 provides a layered network perspective of a point
42、-to-multipoint connection according to the architecture defined in ITU-T G.8110.1. This single layer network view can be used to describe the point-to-multipoint. A unidirectional point-to-multipoint network connection broadcasts the traffic from the root T-MPLS TCP to the leaf T-MPLS TCPs as illust
43、rated in Figure 4. Figure 4 Point-to-multipoint T-MPLS connection A unidirectional point-to-multipoint subnetwork connection broadcasts the traffic from the root T-MPLS CP to the leaf T-MPLS CPs as illustrated in Figure 5. The broadcast function provided by the point-to-multipoint subnetwork connect
44、ion is limited to the subnetwork in which it exists. It may form part of a broadcast function within a larger (containing) subnetwork or network connection. 6 Y series Supplement 4 (01/2008) Figure 5 Point-to-multipoint T-MPLS subnetwork connection 7 Motivation for OAM functionalities for T-MPLS-bas
45、ed networks It is recognized that OAM functionality is important in transport networks for ease of network operation, for verifying network performance, and to reduce operational complexity. OAM functionality is especially important for networks that are required to deliver (and hence be measurable
46、against) network performance and availability objectives. In order to offer a reliable service over a T-MPLS layer network that can support the requirements of a service level agreement (SLA), it is necessary that the T-MPLS layer network has OAM capabilities. The major motivations for T-MPLS OAM ar
47、e discussed further below. 1) A T-MPLS layer network makes use of the connection-oriented mode of the MPLS forwarding plane. The MPLS label stacking capability as described in ITU-T G.8110 allows the creation of multiple T-MPLS sublayers. Each of these is provided with the same OAM functions. It sho
48、uld be noted that OAM functions can be deployed on a per layer network instance and hierarchical basis. Detection of faults in a T-MPLS sublayer must not rely upon detection in other sublayers or layer networks, above or below. 2) Operators need the ability to determine T-MPLS availability and netwo
49、rk performance, noting that network performance metrics are only meaningful when the connection is in the available state. In addition, the OAM helps to reduce operating complexity by allowing efficient and automatic detection, handling and diagnosis of defects. For further information see clauses 7 and 10 of ITU-T G.7710. 3) Provide services that support FCAPS functionality, as described in ITU-T M.3400, that are utilized to improve operational availabi
