1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T Y.1412TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (11/2003) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT GENERATION NETWORKS Internet protocol aspects Interworking ATM-MPLS network interworking Frame mode user plane
2、interworking ITU-T Recommendation Y.1412 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 Interface
3、s 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 capabilities and
4、 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 architect
5、ure 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 Y.2400Y.
6、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.1412 (11/2003) i ITU-T Recommendation Y.1412 ATM-MPLS network interworking Frame mode user plane
7、interworking Summary This Recommendation addresses the required functions for network interworking between ATM networks and MPLS networks, specifically the user plane interworking mechanisms and procedures. One of the key aspects of network interworking is to provide network support for ATM services
8、 during the evolution of networks. Details of the interworking model and required interworking functions are described. Source ITU-T Recommendation Y.1412 was approved by ITU-T Study Group 13 (2001-2004) under the ITU-T Recommendation A.8 procedure on 6 November 2003. ii ITU-T Rec. Y.1412 (11/2003)
9、FOREWORD The International Telecommunication 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
10、issuing Recommendations on 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
11、 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 necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expres
12、sion “Administration“ is 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 applicabilit
13、y) and compliance with 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 Reco
14、mmendation is required 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 o
15、f claimed Intellectual 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
16、Recommendation. However, implementors are cautioned that this 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
17、permission of ITU. ITU-T Rec. Y.1412 (11/2003) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 2 4 Abbreviations 2 5 ATM-MPLS interworking 4 6 General requirements 4 6.1 User plane requirements. 4 6.2 Control plane aspects 5 6.3 Management plane aspects. 6 6.4 Traffic management aspects. 6
18、 7 Methods for ATM transport over MPLS 7 7.1 AAL type 5 PDU mode 7 7.2 AAL type 5 SDU mode 7 7.3 Functional group considerations for ATM-MPLS network interworking . 8 8 AAL type 5 PDU mode encapsulation . 10 8.1 Transport label 10 8.2 Interworking label 10 8.3 Common interworking indicators. 10 8.4
19、ATM-MPLS interworking specific header. 11 8.5 Payload . 11 8.6 Encapsulation . 11 8.7 AAL type 5 PDU frame fragmentation 12 8.8 Procedure at the egress IWF. 12 9 AAL type 5 SDU mode encapsulation . 13 9.1 Transport label 13 9.2 Interworking label 13 9.3 Common interworking indicators. 13 9.4 ATM-MPL
20、S interworking specific header. 14 9.5 Payload . 14 9.6 Encapsulation . 14 9.7 Procedures at the egress IWF . 15 10 OAM and RM cell treatment 16 10.1 ATM-to-MPLS direction 16 10.2 MPLS-to-ATM direction 17 11 Security considerations. 17 Appendix I Bibliography 17 iv ITU-T Rec. Y.1412 (11/2003) Introd
21、uction There is a need to focus on the functions required for network interworking between ATM networks and MPLS networks, specifically the user plane interworking mechanisms and procedures. One of the key aspects of network interworking is to provide network support for ATM services during the evol
22、ution of networks. ITU-T Rec. Y.1412 (11/2003) 1 ITU-T Recommendation Y.1412 ATM-MPLS network interworking Frame mode user plane interworking 1 Scope This Recommendation focuses on the functions required for network interworking between ATM and MPLS, specifically the user plane interworking mechanis
23、ms and procedures for the AAL type 5 protocol data unit (PDU) and service data unit (SDU) transport modes. In particular, it specifies a list of requirements, interworking scenarios and interworking encapsulation formats and semantics for ATM-MPLS AAL type 5 PDU and SDU mode network interworking. Th
24、is Recommendation enables transport of ATM PVC or SVC connections over an MPLS network. The encapsulation allows one AAL type 5 CPCS PDU or SDU to be carried within a single MPLS label switched path (LSP). The scope includes support of AAL type 5, transport of OAM and RM cells. 2 References The foll
25、owing ITU-T Recommendations and other references contain provisions 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 Reco
26、mmendation are therefore encouraged to investigate the possibility 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
27、 give it, as a stand-alone document, the status of a Recommendation. 1 IETF RFC 3031 (2001), Multiprotocol Label Switching Architecture. 2 ITU-T Recommendation I.610 (1999), B-ISDN operation and maintenance principles and functions. 3 ITU-T Recommendation I.610 (1999)/Corrigendum 1 (2000), B-ISDN op
28、eration and maintenance principles and functions. 4 ITU-T Recommendation I.610 (1999)/Amendment 1 (2000), B-ISDN operation and maintenance principles and functions. 5 ITU-T Recommendation Y.1710 (2002), Requirements for Operation and Maintenance functionality in MPLS networks. 6 ITU-T Recommendation
29、 Y.1711 (2002), Operation and Maintenance mechanism for MPLS networks. 7 ITU-T Recommendation I.371 (2000), Traffic control and congestion control in B-ISDN. 8 ITU-T Recommendation I.371.1 (2000), Guaranteed frame rate ATM transfer capability. 9 ITU-T Recommendation I.356 (2000), B-ISDN ATM layer ce
30、ll transfer performance. 10 IETF RFC 3270 (2002), Multi-Protocol Label Switching (MPLS) Support of Differentiated Services. 11 IETF RFC 3032 (2001), MPLS Label Stack Encoding. 12 ITU-T Recommendation I.732 (2000), Functional characteristics of ATM equipment. 13 ATM Forum af-sec-0100.002 (2001), ATM
31、Security Specification Version 1.1. 2 ITU-T Rec. Y.1412 (11/2003) 14 ITU-T Recommendation I.363.5 (1996), B-ISDN ATM Adaptation Layer specification: Type 5 AAL. 15 ITU-T Recommendation Y.1411 (2003), ATM-MPLS network interworking Cell mode user plane interworking. 17 FR Forum Implementation Agreemen
32、t FRF.8.1 (2000), Frame Relay/ATM PVC service interworking implementation agreement. 18 ITU-T Recommendation I.361 (1999), B-ISDN ATM layer specification. 19 ITU-T Recommendation I.510 (1993), Definitions and general principles for ISDN interworking. 3 Definitions This Recommendation defines the fol
33、lowing terms: 3.1 interworking: The term interworking is used to express interactions between networks, between end systems, or between parts thereof, with the aim of providing a functional entity capable of supporting an end-to-end communication. The interactions required to provide a functional en
34、tity rely on functions and on the means to select these functions 19. 3.2 interworking function (IWF): These functions are referred to in the interworking definition, which include the conversion between protocols and the mapping of one protocol to another. The functionality required between network
35、s can be separated from the functionality, if any, required in end systems. The IWFs needed as a result of a service requirement for interworking are categorized as connection-dependent IWFs (i.e., those functions needed in order to interconnect two networks) or communication-dependent IWFs (i.e., t
36、hose functions in addition to connection-dependent IWFs needed in order to establish a specific end-to-end communication and which may differ from application to application) 19. The IWF includes interworking between U-plane, C-plane and M-plane functions. 3.3 ingress IWF/network element: The point
37、where the AAL type 5 PDUs or SDUs are encapsulated into an MPLS packet (ATM-to-MPLS direction). 3.4 egress IWF/network element: The point where the AAL type 5 PDUs or SDUs are de-encapsulated from an MPLS packet (MPLS-to-ATM direction). 3.5 MPLS packet payload: The MPLS packet payload is comprised o
38、f the common interworking indicators, the ATM-MPLS interworking specific header and the payload. The length of the MPLS packet payload is expressed in number of octets. 4 Abbreviations This Recommendation uses the following abbreviations. AAL ATM Adaptation Layer AINI ATM Inter-Network Interface ATC
39、 ATM Transfer Capability ATM Asynchronous Transfer Mode ATM-F ATM Forum AUU ATM User-to-User indication CES Circuit Emulation Service CLP Cell Loss Priority ITU-T Rec. Y.1412 (11/2003) 3 CPCS Common Part Convergence Sub-layer CPCS-UU CPCS User-to-User indication CPI Common Part Indicator CRC Cyclic
40、Redundancy Check DSS2 Digital Subscriber Signalling System No. 2 E-LSP EXP-inferred-PSC LSP EFCI Explicit Forward Congestion Indication EXP Experimental Bit FIFO First-In First-Out ILMI Integrated Local Management Interface IP Internet Protocol ISH Interworking Specific Header IWF InterWorking Funct
41、ion L-LSP Label-only-inferred-PSC LSP LSP Label Switched Path LSR Label Switching Router MPLS Multi-Protocol Label Switching MTU Maximum Transport Unit OAM Operation and Maintenance PDU Protocol Data Unit PHB Per Hop Behaviour PM Performance Monitoring PNNI Private Network-to-Network Interface PSC P
42、HB Scheduling Class PTI Payload Type Identifier PVC Permanent Virtual Circuit QoS Quality of Service RFC Request For Comments RM Resource Management S-bit Stack bit SAP Service Access Point SDU Service Data Unit SPVC Soft PVC SVC Switched Virtual Circuit TTL Time To Live UNI User-Network Interface U
43、U User-to-User 4 ITU-T Rec. Y.1412 (11/2003) VC Virtual Channel VCC Virtual Channel Connection VCI Virtual Channel Identifier VP Virtual Path VPC Virtual Path Connection VPI Virtual Path Identifier 5 ATM-MPLS interworking The multi-protocol label switching (MPLS) technology 1 allows services to be s
44、upported over a single networking infrastructure. Services in this context are traditional data services such as ATM, Frame Relay, IP and circuit emulation services (CES). Figure 5.1 provides the reference network architecture for ATM-MPLS network interworking where ATM network(s) are interconnected
45、 through an MPLS network. For the ATM-to-MPLS direction, an AAL type 5 PDU, AAL type 5 PDU fragment or an AAL type 5 SDU are encapsulated in an MPLS packet by the interworking function. For the MPLS-to-ATM direction, reconstruction of the ATM cells is performed. Y.1412_F5.1LSPMPLSATMATMIWFATMIWFLSRA
46、TMATM network MPLS network ATM networkMPLS MPLSEnd system 1End system 2Figure 5.1/Y.1412 Reference network architecture for ATM-MPLS network interworking 6 General requirements 6.1 User plane requirements For transparent transfer of ATM-related information in the transfer (user) plane, the following
47、 are required: a) The ability to multiplex multiple ATM VCCs into a transport LSP. b) Support for the traffic contracts and the QoS commitments made to the ATM connections. c) The ability to transparently carry all OAM cells, including the support for proper operation of OAM PM cells. d) Transport o
48、f resource management (RM) cells. e) Transport of cell loss priority (CLP) indication and explicit forward congestion indication (EFCI) information from AAL type 5 frame. f) Maintaining frame sequence integrity for AAL type 5 PDU, AAL type 5 PDU fragment or AAL type 5 SDU. g) Support of ATM point-to
49、-point and ATM point-to-multipoint connections. h) Support of bidirectional ATM point-to-point connections with symmetric or asymmetric bandwidth. ITU-T Rec. Y.1412 (11/2003) 5 i) Support for transparent transport of ATM signalling protocols (e.g., DSS2, B-ISUP, ATM-F UNI, ATM-F PNNI, ATM-F AINI), ATM routing protocols (e.g., ATM-F PNNI) and ATM management protocols (e.g., ATM Forum ILMI), which control the ATM connections across the MPLS network. j) Support of a mechanism to associate the two transport LSPs,
