1、 International Telecommunication Union ITU-T Y.1417/Q.3151TELECOMMUNICATION 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 ATM and frame relay/MPLS control plane interworking: Client-server ITU-T Recommendation Y.1417/Q.3151 ITU-T Y-SERIES RECOMMENDATIONS GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS GLOBAL INFO
3、RMATION 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.899 INTER
4、NET 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 Operation,
5、 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: Interope
6、rability 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 of ITU-T
7、Recommendations. ITU-T Rec. Y.1417/Q.3151 (06/2007) i ITU-T Recommendation Y.1417/Q.3151 ATM and frame relay/MPLS control plane interworking: Client-server Summary ITU-T Recommendation Y.1417/Q.3151 defines the control plane and control protocol client-server interworking procedures for ATM and fram
8、e relay connections across an IP/MPLS packet-switched network using pseudo wires. Source ITU-T Recommendation Y.1417/Q.3151 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.1417/Q.3151 (06/2007) FOREWORD The International
9、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 issuing Recommendations on
10、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 topics. The approval of IT
11、U-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 expression “Administration“ is us
12、ed 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 applicability) and compliance with the
13、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 Recommendation is required of a
14、ny 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 of claimed Intellectual Prop
15、erty 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 Recommendation. However, im
16、plementers 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 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior wri
17、tten permission of ITU. ITU-T Rec. Y.1417/Q.3151 (06/2007) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 1 4 Abbreviations and acronyms 1 5 Conventions 2 6 Requirements 2 7 Architecture 3 7.1 Client-pseudo wire control plane interactions 4 8 The pseudo wire control plane 5 9 The client c
18、ontrol plane 5 9.1 Logical links . 6 9.2 Establishment of control pseudo wires. 6 10 ATM and FR to LDP signalling interworking 8 10.1 ATM and FR to LDP signalling interworking procedures. 8 10.2 The SAI and the TAI in LDP signalling. 11 Bibliography. 12 iv ITU-T Rec. Y.1417/Q.3151 (06/2007) Introduc
19、tion Many network providers are offering and delivering VC-based services across dedicated frame relay and ATM networks. Many of these same providers have embarked upon a strategy of convergence where many per-service networks and their attendant technologies and services are migrated to a single IP
20、/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 operate over this multi-service converged PSN. ATM networks employ dynamic signalling and routing protocols to expedite connection setup and
21、 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 to a PSN, service providers will expect their existing ATM operations infrastructure to work with minimal modifications. In particular,
22、 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-IETF RFC 3985 to emulate services over a PSN. Specifically, b-IETF RFC 4717 defines how to emulate ATM connections over a PSN. These
23、specifications, however, only describe the data plane behaviour. They do not define how an ATM connection setup interacts with PW setup. Other methods enabling switched connection setup across an MPLS network have been defined in b-ITU-T Y.1416 and b-ATM cs-0197. In these approaches, each connection
24、 setup or teardown in the client control plane triggers the setup or teardown of a corresponding 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 t
25、he MPLS core network IETF terminology is used (e.g., pseudo wire, PE, etc.). This Recommendation covers issues with client-server interworking. 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.1416. ITU-T Rec. Y.1417/Q.3151 (0
26、6/2007) 1 ITU-T Recommendation Y.1417/Q.3151 ATM and frame relay/MPLS control plane interworking: Client-server 1 Scope This Recommendation defines the control plane and control protocol interworking procedures for ATM and frame relay connections across an IP/MPLS packet-switched network using pseud
27、o wires. The following items are not within the scope of this Recommendation: Peer-partition interworking between ATM and frame relay control planes. Peer-partition interworking between ATM (or frame relay) and IP/MPLS control planes for setting up and managing switched connections between ATM (or f
28、rame relay) and IP/MPLS end-points. L2TPv3 pseudo wires b-IETF RFC 3931. 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 of publication, the editions indicated we
29、re 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 list of the currently valid ITU-T Recommend
30、ations 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. IETF RFC 3036 IETF RFC 3036 (2001), LDP Specification. IETF RFC 4447 IETF RFC 4447 (2006), Pseudowire Setup and Maintenance using the Lab
31、el Distribution Protocol (LDP). ATM pnni-0055 ATM Forum af-pnni-0055.002 (2002), Private Network-Network Interface Specification Version 1.1. 3 Definitions None. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: AINI ATM Inter-Network Interface ATM Async
32、hronous Transfer Mode BGP Border Gateway Protocol DSS2 Digital Subscriber Signalling System No. 2 IGP Interior Gateway Protocol IP Internet Protocol LDP Label Distribution Protocol LER Label Edge Router 2 ITU-T Rec. Y.1417/Q.3151 (06/2007) LSP Label Switched Path MP-BGP Multi-Protocol BGP MPLS Multi
33、-Protocol Label Switching NNI Network Node Interface PNNI Private Network-Network Interface PSN Packet Switched Network PW Pseudo Wire PWE3 Pseudo wire Emulation Edge-to-Edge group RSVP-TE Resource Reservation Protocol Traffic Engineering UNI User Network Interface VC Virtual Connection VCI Virtual
34、Connection Identifier VPI Virtual Path Identifier VPN Virtual Private Network 5 Conventions None. 6 Requirements The requirements for the client-server control plane interworking functions include: The architecture should allow and support a wide range of ATM and frame relay control plane protocols,
35、 including intra-network 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 dime
36、nsions, to allow it to be used effectively 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 curren
37、t client networks. 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
38、required to support 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 a
39、voided if at all possible. Support multiple ATM services classes efficiently. ITU-T Rec. Y.1417/Q.3151 (06/2007) 3 7 Architecture Figure 1 depicts the high-level architecture. Client networks operating a native client (routing and signalling) control plane attached to label edge routers (LER) that a
40、re part of an IP/MPLS PSN. The LERs operate an IP/MPLS control plane (e.g., IGP/BGP, LDP, PWE3, RSVP-TE, etc.) to set up and manage label switched paths (LSP) across the network. The LERs also operate one or more instances of a co-located client control plane or may interface to a client control pla
41、ne running on a separate physical or logical device. Client network control plane messages used to dynamically route, set up, manage and tear down client network point-to-point connections (e.g., PNNI) are processed by client network devices and the client control plane instance physically or logica
42、lly affiliated with the corresponding LER. Receipt of client control plane messages by an LER will dynamically trigger the corresponding IP/MPLS server network control plane functions necessary to carry encapsulated client network payloads contained in pseudo wires across the IP/MPLS PSN from one cl
43、ient network device to another. The high-level design principles behind this solution are: Separation of client and pseudo wire (IP/MPLS) control planes. Some interaction may take place between the control planes but that interaction should be constrained and should allow each to be essentially unaw
44、are of the technical details of the other. (The mechanism and interface for interaction, known as the pseudo wire service interface, are not issues for standardization.) Optional use of aggregation functionality at the edge of the client network, enables separation of client control and pseudo wire
45、control in different devices. Use of IETF defined PW control mechanisms as the PW control plane in all scenarios except those with a null PW control plane. Other PW control plane mechanisms are not precluded. b-ITU-T Q.2920 has previously defined techniques that enable switched connection setup acro
46、ss an MPLS network. The client networks are ATM and the client control plane is DSS2. Extensions are defined for DSS2 to signal PW labels between the MPLS edge devices. The client and PW control functions are collapsed into a single protocol. The solution defined in this Recommendation opts for a di
47、fferent approach by decoupling the client and PW control planes so as to lessen the dependencies of one on the other. Each is allowed to operate and evolve separately from the other. It also enables different client control planes (e.g., frame relay) to employ the same PW control plane. Conversely d
48、ifferent PW control planes depending on the PSN type (i.e., MPLS or IP) may be used to support client networks. The architecture allows two scenarios: one in which both control planes run on the same physical internetworking element at the edge of the MPLS network; the other allowing for separation
49、of client control and pseudo wire control in different physical (or possibly logical) devices. 4 ITU-T Rec. Y.1417/Q.3151 (06/2007) Figure 1 High-level architecture A packet-switched network (PSN) provides MPLS infrastructure to support pseudo wires. A label edge router (LER) provides an interworking function (IWF) that connects the PSN and a segment of the client network. In the user plane, the LER interworks each client virtual connection, including virtual connections for control and management, with
