1、 International Telecommunication Union ITU-T Y.1223TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (07/2008) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS Internet protocol aspects Architecture, access, network capabilities and resource managemen
2、t Interworking guidelines for transporting assured IP flows Recommendation ITU-T Y.1223 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
3、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 applications Y.1100Y.1199
4、 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 NEXT GENERATI
5、ON 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, naming and addr
6、essing 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. Rec. ITU-T Y.1223 (07/2008) i Recommendation ITU-T Y.1223 Inter
7、working guidelines for transporting assured IP flows Summary In order to transport IP flows with assured end-to-end quality and reliability in a multi-provider environment, coordinated decisions must be made regarding the admission, policing, and assignment of resources to particular offered flows.
8、To do this, a uniform way of characterizing such IP flows is needed, and some shared decision rules for handling them. Recommendation ITU-T Y.1223 defines a set of IP flow specifications that could offer a basis for such cooperation. Source Recommendation ITU-T Y.1223 was approved on 14 July 2008 by
9、 ITU-T Study Group 12 (2005-2008) under Recommendation ITU-T A.8 procedure. Keywords IP, IP flows, IP priority, IP QoS, IP traffic, Pspec, QoS, Qspec, Tspec. ii Rec. ITU-T Y.1223 (07/2008) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field
10、of telecommunications, information and communication technologies (ICTs). 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 them with a view to standardizing
11、 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 ITU-T Recommendations is covered by
12、 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 used for conciseness to indicate bo
13、th 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 Recommendation is achieved when a
14、ll 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 any party. INTELLECTUAL PROPERTY R
15、IGHTS 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 Property Rights, whether asserted by
16、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, implementers are cautioned that thi
17、s 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 2009 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-
18、T Y.1223 (07/2008) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 1 4 Abbreviations and acronyms 2 5 Conventions 2 6 Interworking guidelines for transporting assured IP flows. 2 6.1 IP flow specifications . 3 6.2 Using IP flow specifications in network planning and operation. 6 6.3 Furthe
19、r study items. 9 Annex A Definition of IP flow parameters using the continuous-state token bucket algorithm. 10 Bibliography. 11 iv Rec. ITU-T Y.1223 (07/2008) Introduction A major challenge facing network providers in transporting IP flows with assured quality and reliability levels is the fact tha
20、t several independently-operated networks, using different QoS control and resource management technologies, will typically share the responsibility for providing the end-to-end services. This Recommendation addresses this challenge by extracting, from existing standards, a set of flow specification
21、s that network operators need to share in making coordinated admission, policing, and resource assignment decisions for offered IP flows. This Recommendation also suggests a set of basic decision rules that cooperating network providers could follow, in interpreting and acting on such shared informa
22、tion, to ensure that the end-to-end quality and reliability requirements of admitted flows are consistently met. Recommendation ITU-T Y.1540 provides the parameters and definitions for IP QoS; Recommendation ITU-T Y.1541 gives a set of end-to-end IP QoS classes with numerical objectives for these pa
23、rameters; and Recommendation ITU-T Y.1542 provides a framework of approaches for achieving end-to-end IP QoS. This Recommendation is the logical next step in this sequence a uniform way of dealing with IP flows, so that multiple providers have a basis for coordinating to deliver end-to-end IP QoS wi
24、th assured quality and reliability. Rec. ITU-T Y.1223 (07/2008) 1 Recommendation ITU-T Y.1223 Interworking guidelines for transporting assured IP flows 1 Scope This Recommendation provides a set of specifications for characterizing IP flows requiring assured quality and reliability levels, and ident
25、ifies possible decision rules for interpreting and processing that information to ensure that the requested quality and reliability requirements of admitted flows are consistently met. Extracted from existing standards, a set of flow specifications is provided that network operators need to share in
26、 making coordinated admission, policing, and resource assignment decisions for offered IP flows. A set of basic decision rules are suggested that cooperating network providers could follow, in interpreting and acting on such shared information, to ensure that the end-to-end quality and reliability r
27、equirements of admitted flows are consistently met. This Recommendation makes no assumptions about how the shared information is exchanged among cooperating network providers. The focus here is on the semantics and processing of the shared information, rather than on how it is exchanged. 2 Reference
28、s 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 were valid. All Recommendations and other references are subject to revision; users of
29、 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 Recommendations is regularly published. The reference to a document within this Recommendatio
30、n does not give it, as a stand-alone document, the status of a Recommendation. ITU-T Y.1221 Recommendation ITU-T Y.1221 (2002), Traffic control and congestion control in IP-based networks. ITU-T Y.1540 Recommendation ITU-T Y.1540 (2007), Internet protocol data communication service IP packet transfe
31、r and availability performance parameters. ITU-T Y.1541 Recommendation ITU-T Y.1541 (2006), Network performance objectives for IP-based services. ITU-T Y.1542 Recommendation ITU-T Y.1542 (2006), Framework for achieving end-to-end IP performance objectives. ITU-T Y.2111 Recommendation ITU-T Y.2111 (2
32、006), Resource and admission control functions in Next Generation Networks. ITU-T Y.2171 Recommendation ITU-T Y.2171 (2006), Admission control priority levels in Next Generation Networks. ITU-T Y.2172 Recommendation ITU-T Y.2172 (2007), Service restoration priority levels in Next Generation Networks
33、. 3 Definitions This Recommendation defines the following terms: 3.1 Qspec: A set of QoS-related IP flow parameters (extracted from existing standards). 3.2 Pspec: A set of Priority-related IP flow parameters (extracted from existing standards). 2 Rec. ITU-T Y.1223 (07/2008) 3.3 Tspec: A set of Traf
34、fic-related IP flow parameters (extracted from existing standards). 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: AS Autonomous System ASBR Autonomous System Border Router DiffServ Differentiated Services EXP bits Experimental bits (used to support D
35、iffServ) in the MPLS header FIFO First In, First Out IP Internet Protocol IPDV IP Packet Delay Variation IPLR IP Packet Loss Ratio IPTD IP Packet Transfer Delay ISP Internet Service Provider MPLS MultiProtocol Label Switching OAM Operations, Administration and Maintenance QoS Quality of Service SLA
36、Service Level Agreement VoIP Voice over Internet Protocol VPN Virtual Private Network 5 Conventions There are no conventions specific to this Recommendation. 6 Interworking guidelines for transporting assured IP flows End-to-end, IP-based service delivery is typically shared by several independently
37、-operated networks, often using different QoS control and resource management technologies. Previous studies b-T1A1/2003-133 and b-PRQC have identified the general elements of a standards-based approach to this problem, and a number of standards (e.g., ITU-T Y.1221, ITU-T Y.1541, ITU-T Y.2111 and b-
38、IETF RFC 4804) have addressed particular solution elements. The next step is to produce a set of standards-based flow specifications that network operators need to share in making coordinated admission, policing, and resource assignment decisions for offered IP flows. Also needed is a set of basic d
39、ecision rules that cooperating network providers could follow, in interpreting and acting on shared information, to ensure that end-to-end quality and reliability requirements of admitted flows are consistently met. No assumptions are made here regarding how the shared information is exchanged among
40、 cooperating network providers. At one extreme of complexity (and flexibility), the information could be explicitly encoded in signalling messages and communicated among providers on a per-flow basis, e.g., using procedures like those defined in b-ITU-T Q-Sup.51 or ITU-T Y.2111. At the other extreme
41、, the shared information could be captured in static network management databases derived from inter-provider service level agreements (SLAs) or known network attributes, and no explicit signalling of IP flow specifications might be needed. In intermediate situations, the shared information could be
42、 communicated indirectly through other signalled information (e.g., Rec. ITU-T Y.1223 (07/2008) 3 Ethernet traffic types, DiffServ code points, MPLS EXP bits). In some cases, the shared information could be inferred from routing information, VPN addresses, service classes, or topological cues, such
43、as the ingress or egress port at which a particular flow appears. The focus here is on the semantics and processing of the shared information, rather than how on it is exchanged. To simplify the problem, we focus on the general interworking model shown in Figure 1. The figure depicts two independent
44、ly-operated networks (Ni and Nj), which represent separate domains or autonomous systems (ASs) connected to each other (and potentially, to other networks or to user equipment) by a number of links between autonomous system border routers (ASBRs). Ni and Nj are independently administered and are vie
45、wed as separate entities from a modelling point of view. They may be comprised internally of multiple ASs. In general, the two networks will have different internal topologies, point-to-point transmission capacities, and point-to-point QoS characteristics. Their instantaneous offered and carried tra
46、ffic levels will also differ. They may use different internal transport technologies, signalling protocols, and routing protocols. Their internal admission control, policing, and resource assignment policies and mechanisms may also differ. Despite these differences, the network operators will need t
47、o find ways to cooperate based on certain shared information, in transporting IP flows. Their mutual goal is to accept and successfully transport a high proportion of offered IP flows, requiring a wide range of assured quality and reliability levels, under widely varying network conditions including
48、, inter alia, variable offered and carried traffic levels, variable network topologies and routing states, and variable impairment levels on particular transmission paths. Figure 1 General interworking model This rest of this clause addresses the information about offered IP flows (and the ability o
49、f a network to support them) to be shared among concatenated networks (e.g., Ni, Nj) so that networks cooperate successfully in transporting IP flows with assured quality and reliability levels. 6.1 IP flow specifications It is suggested that IP flows requiring assured quality and reliability levels can be described, from a technical (non-administrative) point of view, in terms of three types of IP flow specifications: a traffic specification (Tspec), a priority specification (Pspec), and a quality specification (Qspec).
