1、 International Telecommunication Union ITU-T Y.1416/Q.3150TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (06/2007) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS Internet protocol aspects Interworking SERIES Q: SWITCHING AND SIGNALLING Signalling
2、 requirements and protocols for the NGN Bearer control signalling Use of virtual trunks for ATM/MPLS client/server control plane interworking ITU-T Recommendation Y.1416/Q.3150 ITU-T Y-SERIES RECOMMENDATIONS GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS GL
3、OBAL INFORMATION INFRASTRUCTURE General Y.100Y.199 Services, applications and 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.
4、899 INTERNET PROTOCOL ASPECTS General Y.1000Y.1099 Services and applications 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 O
5、peration, administration and maintenance Y.1700Y.1799 Charging Y.1800Y.1899 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:
6、 Interoperability of services and networks in NGN Y.2250Y.2299 Numbering, naming 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
7、of ITU-T Recommendations. ITU-T Rec. Y.1416/Q.3150 (06/2007) i ITU-T Recommendation Y.1416/Q.3150 Use of virtual trunks for ATM/MPLS client/server control plane interworking Summary The virtual trunk approach provides a mechanism in which pseudo wires function as trunks through which ATM switches ca
8、n transparently establish and maintain virtual channel connections (VCCs) and virtual path connections (VPCs). The virtual trunk approach decouples control plane activity in the ATM and MPLS control planes, and pseudo wire setup or teardown is requested explicitly. Source ITU-T Recommendation Y.1416
9、/Q.3150 was approved on 13 June 2007 by ITU-T Study Group 13 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. Y.1416/Q.3150 (06/2007) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU T
10、elecommunication 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 standardizing telecommunications on a worldwide basis. The World Telecommunication Standardizati
11、on 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 by the procedure laid down in WTSA Resolution 1. In some areas of information technol
12、ogy 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 both a telecommunication administration and a recognized operating agency. Compliance
13、 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 all of these mandatory provisions are met. The words “shall“ or some other obligator
14、y 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 RIGHTS ITU draws attention to the possibility that the practice or implementation of
15、 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 by ITU members or others outside of the Recommendation development process. As of the
16、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, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to cons
17、ult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2008 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.1416/Q.3150 (06/2007) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions
18、 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Recommendation. 2 4 Abbreviations and acronyms 2 5 Conventions 3 6 Requirements 3 7 Introduction to virtual trunks 3 7.1 Pseudo wire emulation and related terminology 3 7.2 Virtual trunks 4 7.3 Implementation options 6 8 Virtual trunk proced
19、ures distributed implementation 7 8.1 Definition of virtual trunks on an ATM interface 7 8.2 ME procedures 8 8.3 Simplified assignments. 9 8.4 QoS. 11 9 Virtual trunk data plane procedures integrated implementation 12 9.1 Encapsulation . 12 9.2 ATM control interface 12 9.3 QoS. 12 9.4 Usable VPIs wi
20、thin a VT 12 10 Signalling procedures between ATM switches connected through a virtual trunk 13 11 Virtual trunk setup and maintenance 13 11.1 Virtual trunk configuration. 13 12 Virtual trunk OAM . 14 12.1 Defects and consequent actions 14 Annex A Support of both virtual trunks and individual VCs on
21、 the same ATM interface 16 Appendix I VPI range as local parameter . 17 Bibliography. 18 iv ITU-T Rec. Y.1416/Q.3150 (06/2007) Introduction Many network providers are offering and delivering VC-based services across dedicated frame relay and ATM networks. Many of these same providers have embarked u
22、pon a strategy of convergence where many per-service networks and their attendant technologies and services are migrated to a single IP/MPLS packet-switched network (PSN). It is envisaged that existing network services such as frame relay and ATM and emerging new services including IP VPN will opera
23、te over this multi-service converged PSN. ATM networks employ dynamic signalling and routing protocols to expedite connection setup and recovery. PNNI is an example of one such protocol used to dynamically set up switched ATM connections across a native ATM network ATM pnni-0055. When transitioning
24、to a PSN, service providers will expect their existing ATM operations infrastructure to work with minimal modification. In particular, control protocols for routing and signalling must continue to work end-to-end. The Internet Engineering Task Force (IETF) has developed pseudo wire (PW) technology b
25、-IETF RFC 3985 to emulate services over a PSN. Specifically, IETF RFC 4717 defines how to emulate ATM connections over a PSN. These specifications, however, only describe the data plane behaviour. They do not define how an ATM connection setup interacts with PW setup. The virtual trunk approach prov
26、ides a mechanism in which pseudo wires function as trunks through which ATM switches can transparently establish and maintain virtual channel connections (VCCs) and virtual path connections (VPCs). The virtual trunk approach decouples control plane activity in the ATM and MPLS control planes, and ps
27、eudo-wire setup or teardown is requested explicitly. Other methods enabling switched connection setup across an MPLS network have been defined in b-ITU-T Y.1417 and b-ATM cs-0197. In these approaches, each connection setup or teardown in the client control plane triggers the setup or teardown of a c
28、orresponding pseudo wire. The terminology used in this Recommendation is based upon the terminology associated with the control and user plane protocols of the organization responsible for them. For example, within the MPLS core network IETF terminology is used (e.g., pseudo wire, PE). This Recommen
29、dation covers issues with virtual trunks. It is one of a set of documents addressing control plane interworking of MPLS with ATM and frame relay. See also b-ITU-T Y.1417. ITU-T Rec. Y.1416/Q.3150 (06/2007) 1 ITU-T Recommendation Y.1416/Q.3150 Use of virtual trunks for ATM/MPLS client/server control
30、plane interworking 1 Scope This Recommendation defines virtual trunks, their mapping to pseudo wires, and the way ATM switches establish connections through them. The virtual trunk approach provides a mechanism in which pseudo wires function as trunks through which ATM switches can transparently est
31、ablish and maintain virtual channel connections (VCCs) and virtual path connections (VPCs). This approach has two objectives: Minimize the amount of interactions between the ATM control plane and the MPLS control plane. Enable a distributed interworking approach in which ATM control plane and PW con
32、trol plane may be on different interworking devices. This enables separation of the MPLS network routing domains and the ATM routing domains. The following items are not within the scope of this Recommendation: Peer-partition interworking between ATM and frame relay control planes. Peer-partition in
33、terworking between ATM (or frame relay) and IP/MPLS control planes for setting up and managing switched connections between ATM (or frame relay) and IP/MPLS end-points. L2TPv3 pseudo wires b-IETF RFC 3931. Signalling to establish virtual trunks. 2 References The following ITU-T Recommendations and o
34、ther 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 Recommendation are therefore encourag
35、ed 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 give it, as a stand-alone docume
36、nt, the status of a Recommendation. ATM cs-0125 ATM Forum af-cs-0125.001 (2002), ATM Inter-Network Interface (AINI) Specification Version 1.1. ATM pnni-0055 ATM Forum af-pnni-0055.002 (2002), Private Network-Network Interface Specification Version 1.1. ATM tm-0121 ATM Forum af-tm-0121.000 (1999), Tr
37、affic Management 4.1. IETF RFC 4447 IETF RFC 4447 (2006), Pseudowire Setup and Maintenance using the Label Distribution Protocol (LDP). IETF RFC 4717 IETF RFC 4717 (2006), Encapsulation Methods for Transport of Asynchronous Transfer Mode (ATM) over MPLS Networks. 3 Definitions 3.1 Terms defined else
38、where None. 2 ITU-T Rec. Y.1416/Q.3150 (06/2007) 3.2 Terms defined in this Recommendation This Recommendation defines the following term: 3.2.1 virtual trunk: A virtual trunk is a logical connection between two client networks. 4 Abbreviations and acronyms This Recommendation uses the following abbr
39、eviations and acronyms: AC Attachment Circuit AINI ATM Inter-Network Interface ATM Asynchronous Transfer Mode BFD Bidirectional Forwarding Detection CCA Client Connection Aggregation IP Internet Protocol L2E Layer 2 Edge LDP Label Distribution Protocol LER Label Edge Router LSP Label Switched Path M
40、E MPLS Edge MPLS Multi-Protocol Label Switching NNI Network Node Interface OAM Operations, Administration and Management PE Provider Edge PNNI Private Network-Network Interface PSN Packet Switched Network PW Pseudo Wire PWE Pseudo Wire Emulation PWE3 Pseudo Wire Emulation Edge-to-Edge (an IETF worki
41、ng group) RSVP-TE Resource Reservation Protocol Traffic Engineering RVPI Relative VPI UNI User Network Interface VC Virtual Connection VCC Virtual Channel Connection VCI Virtual Connection Identifier VP Virtual Path VPC Virtual Path Connection VPI Virtual Path Identifier VPN Virtual Private Network
42、ITU-T Rec. Y.1416/Q.3150 (06/2007) 3 VT Virtual Trunk VTid Virtual Trunk Identifier 5 Conventions None. 6 Requirements The requirements for the use of virtual trunks consist of: The architecture should allow and support a wide range of ATM and frame relay control plane protocols, including intra-net
43、work and inter-network (NNI) protocols such as PNNI, AINI, IISP, X.76, etc., and UNI protocols such as ATM Forum UNI 3.1 and 4.0, Q.2931, and X.36. Support for these protocols should not be reduced to subsets of functionality. This approach needs to be scalable in a number of dimensions, to allow it
44、 to be effectively used in service provider networks, to support signalling rates commonly found in todays ATM networks, and to allow network growth and expansion. These dimensions include: Performance: This approach should not reduce the signalling capabilities required in current client networks.
45、Network resources: This approach must make effective use of network resources. This architecture should allow to the greatest extent possible the reuse of existing specifications and implementations. In particular: Minimal changes to current ATM and frame relay networks should be required to support
46、 the architecture. Existing IETF mechanisms should be used whenever possible. The use of MPLS network resilience mechanisms is encouraged to allow ATM and FR VCs to survive switch or link outages within the MPLS network if at all possible. ATM and FR-layer VC clearing should be avoided if at all pos
47、sible. Support multiple ATM services classes efficiently. Establishment of virtual trunks by provisioning or signalling. 7 Introduction to virtual trunks This clause introduces virtual trunks. It illustrates the control planes that play a role in the virtual trunk architecture. Finally, it provides
48、reference models for two implementation options. 7.1 Pseudo wire emulation and related terminology In the pseudo wire architecture (b-IETF RFC 3985), provider edge (PE) nodes encapsulate traffic received over an attachment circuit (AC) into a pseudo wire (PW) for transport over a packet-switched net
49、work (PSN). PEs aggregate one or more PWs into a PSN Tunnel. In this architecture, the client protocol is the protocol that is emulated over the PW. A control plane is the combination of routing and signalling protocols that switches use to determine how to forward traffic. In the case of a connection-oriented protocol like ATM, the control plane is used to set up, maintain and tear down connections. The client control plane is the control plane used to manage the client protocol. 4 ITU-T R
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