1、 International Telecommunication Union ITU-T Y.1401TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (02/2008) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS Internet protocol aspects Interworking Principles of interworking Recommendation ITU-T Y.14
2、01 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 Interfaces and protocols Y.400Y.499 Numbering,
3、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 resource management Y.1200Y.1299 Tran
4、sport 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 architecture models Y.2000Y.2099 Quality of Ser
5、vice 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.2499 Network control architectures and
6、 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. Rec. ITU-T Y.1401 (02/2008) i Recommendation ITU-T Y.1401 Principles of interworking Summary Recommendation ITU-T Y.1401 provides an architectural f
7、ramework and general principles for transport stratum interworking in a next generation network (NGN) environment. It describes client/server and peer-partition interworking. Source Recommendation ITU-T Y.1401 was approved on 29 February 2008 by ITU-T Study Group 13 (2005-2008) under Recommendation
8、ITU-T A.8 procedure. Keywords CAL, client/server, interworking, peer-partition. ii Rec. ITU-T Y.1401 (02/2008) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The
9、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 standardizing telecommunications on a worldwide basis. The World Telecommunication Standard
10、ization 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 te
11、chnology 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. Compl
12、iance 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 obli
13、gatory 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 implementati
14、on 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 by ITU members or others outside of the Recommendation development process. As of
15、 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, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to
16、 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 written permission of ITU. Rec. ITU-T Y.1401 (02/2008) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 1
17、 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Recommendation. 1 4 Abbreviations and acronyms 2 5 Conventions 3 6 General aspects of interworking . 3 7 Client/server relationships (network interworking) 5 7.1 General . 5 7.2 Principles of client/server relationships 7 7.3 OAM principles of
18、 client/server relationships . 7 8 Common adaptation layer (CAL) . 7 8.1 General . 7 8.2 CAL principles . 9 8.3 CAL OAM principles. 9 9 Peer-partition interworking (service interworking) 10 9.1 General . 10 9.2 Principles of peer-partition interworking . 13 9.3 OAM principles of peer-partition inter
19、working . 13 10 Control plane interworking. 16 10.1 General . 16 10.2 Network scenarios 16 10.3 Link representation. 17 10.5 Abstract network representation. 20 10.6 Interworking with different network modes. 21 11 Security considerations. 22 Bibliography. 23 Rec. ITU-T Y.1401 (02/2008) 1 Recommenda
20、tion ITU-T Y.1401 Principles of interworking 1 Scope This Recommendation provides an architectural framework and general principles for transport stratum interworking in an NGN environment. It does not attempt to provide details for specific technology scenarios. Rather, it provides fundamental conc
21、epts and principles with illustrative examples. Specific scenarios are covered in other Recommendations. 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 public
22、ation, 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 of applying the most recent edition of the Recommendations and other references listed below. A list of the
23、 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. ITU-T G.805 Recommendation ITU-T G.805 (2000), Generic functional architecture of transport networks. ITU
24、-T G.809 Recommendation ITU-T G.809 (2003), Functional architecture of connectionless layer networks. ITU-T G.8080 Recommendation ITU-T G.8080/Y.1304 (2006), Architecture for the automatically switched optical network (ASON). ITU-T Y.1314 Recommendation ITU-T Y.1314 (2005), Virtual private network f
25、unctional decomposition. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 client/server relationship ITU-T G.805: The association between layer networks that is performed by an “adaptation“ function to allow the link connection in the cl
26、ient layer network to be supported by a trail in the server layer network. 3.1.2 logical external network-network interface (reference point) ITU-T G.8080: The E-NNI is the reference point between domains. 3.1.3 logical internal network-network interface (reference point) ITU-T G.8080: The I-NNI is
27、the reference point within a domain between routing areas and, where required, between sets of control components within routing areas. 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 interworking: The term interworking is used to express interactions
28、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. 2 Rec. ITU-T Y.1401 (02/2008) 3.2.2 interworking function (IWF): These functions are referred to in the interworking definition, which inc
29、lude the conversion between protocols and the mapping of one protocol to another. The functionality required between networks can be separated from the functionality, if any, required in end systems. 3.2.3 message: A symbol selected from a finite set of symbols. NOTE The set of symbols from which a
30、symbol can be chosen is a lexicon (or dictionary). 3.2.4 network interworking: Interworking between two similar (like) networks via an intermediary network with dissimilar characteristics. 3.2.5 open sequence (file): An open sequence is an open-ended sequence of messages, i.e., each symbol value is
31、selected from a finite set of possible values for the symbol. The order of messages in the open sequence carries (implicit) information. An open sequence communication preserves the order of the messages. 3.2.6 peer-partition interworking: In peer-partition interworking, a client networks characteri
32、stic information (CI) is transferred transparently over a concatenation of peered server layer networks. 3.2.7 plane: A category that identifies a collection of related objects, e.g., objects that execute similar or complementary functions; or peer objects that interact to use or to provide services
33、 in a class that reflects authority, capability, or time period. 3.2.8 service interworking: Interworking between two dissimilar (unlike) networks directly without the benefit of an intermediary network. 3.2.9 service level agreement (SLA): A negotiated agreement between an end user and the service
34、provider. Its significance varies depending on the service offerings. The SLA may include a number of attributes such as, but not limited to, traffic contract, availability, performance, encryption, authentication, pricing and billing mechanism, etc. 3.2.10 service plane: The service plane comprises
35、: a) service presentation functionality being presented to the end user; b) service implementation aspects with which the end user interacts, e.g., service invocation, control service level agreement function. NOTE Items a) and b) use the totality of the transfer capabilities including control and m
36、anagement functionalities. 3.2.11 timed sequence (stream): A timed sequence is an open-ended sequence of messages where the timing of each message relative to another is significant. The sequence and the relative time of each symbol carries (implicit) information. A timed sequence communication pres
37、erves both the order of the messages and the timing between each message. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: AP Access Point AS Autonomous System ASON Automatically Switched Optical Network ATM Asynchronous Transfer Mode BDI Backward Defec
38、t Indication CAL Common Adaptation Layer CC Continuity Check Rec. ITU-T Y.1401 (02/2008) 3 CI Characteristic Information cl-ps connectionless packet-switched co connection-oriented co-cs connection-oriented circuit-switched co-ps connection-oriented packet-switched CoS Class of Service CV Connectivi
39、ty Verification E-NNI External Network-Network Interface (as per ITU-T G.8080) FDI Forward Defect Indication I-NNI Internal Network-Network Interface (as per ITU-T G.8080) IWF Interworking Function IWP Interworking Path MPLS MultiProtocol Label Switching NGN Next Generation Network OAM Operations, A
40、dministration and Maintenance PCI Protocol Control Information PNNI Private Network Node Interface QoS Quality of Service SAP Service Access Point SLA Service Level Agreement SLS Service Level Specification TCP Termination Connection Point 5 Conventions This Recommendation uses no specific conventio
41、ns. 6 General aspects of interworking The objective of interworking is to provide some end-to-end communications entity across a single server layer network or across a concatenation of (peered) server layer networks, which may consist of different networking technologies. Throughout this Recommenda
42、tion, an individual server layer network, within such a concatenation of server layer networks, is referred to as a server layer partition. The end-to-end communications entity may be a common higher layer network but may be a common application adaptation function. Fundamentally, there are two inte
43、rworking relationships, “client/server“ and “peer-partition“. They are sometimes known as “network“ and “service“ interworking. More complex interworking relationships can be derived from these two fundamental ones. Client/server interworking describes and defines the way that end-to-end user traffi
44、c is transferred over a single server layer technology. 4 Rec. ITU-T Y.1401 (02/2008) Peer-partition interworking describes and defines the way that end-to-end user traffic is transferred over a concatenation of discrete server layer technology partitions that may belong to different networking mode
45、s. Interworking can take place between any two contiguous layer networks, regardless of their position in the total layer network stack. For example, there is interworking between transmission-media dependent technologies at the lowest level of the total stack and between the application signalling
46、at the highest. Combinations of layer networks in these two interworking relationships can produce complex networks. Therefore, it is important to address interworking from the perspective of the end-to-end user traffic (the client layer) and not just from the perspective of the server layer(s). It
47、is clear that in order to achieve this aim, a client/server relationship must be formed between each of the server layer(s) and their common client layer (i.e., the end-to-end user traffic). The performance experienced by a client entity is dependant on the server layer partitions that it traverses
48、and the performance experienced will ultimately depend on the networking technology and the networking mode that each server layer partition belongs to. More generally because a link connection in layer network N is supported by a trail in layer network N 1, and this is a recursive relationship to t
49、he physical transmission media, the performance impairments experienced by layer network N are a sum (which is not necessarily linear) of the performance impairments inherited from all of the lower layer server networks (down to the physical transmission media) that support layer network N. A given layer network can be defined in terms of the specific semantics and syntax of its user plane traffic units (including user plane OAM functions) and its control plane functions. Provided that the same functional semantics exists in two laye
