1、 International Telecommunication Union ITU-T Y.1541TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (12/2011) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS Internet protocol aspects Quality of service and network performance Network performance ob
2、jectives for IP-based services Recommendation ITU-T Y.1541 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.
3、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 Architecture, access, networ
4、k capabilities and resource management Y.1200Y.1299 Transport Y.1300Y.1399 Interworking Y.1400Y.1499 Quality of service and network performance Y.1500Y.1599Signalling Y.1600Y.1699 Operation, administration and maintenance Y.1700Y.1799 Charging Y.1800Y.1899 IPTV over NGN Y.1900Y.1999 NEXT GENERATION
5、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 address
6、ing Y.2300Y.2399 Network management Y.2400Y.2499 Network control architectures and protocols Y.2500Y.2599 Smart ubiquitous networks Y.2600Y.2699 Security Y.2700Y.2799 Generalized mobility Y.2800Y.2899 Carrier grade open environment Y.2900Y.2999 Future networks Y.3000Y.3099 For further details, pleas
7、e refer to the list of ITU-T Recommendations. Rec. ITU-T Y.1541 (12/2011) i Recommendation ITU-T Y.1541 Network performance objectives for IP-based services Summary This Recommendation defines classes of network quality of service (QoS) with objectives for Internet Protocol network performance param
8、eters. Two of the classes contain provisional performance objectives. These classes are intended to be the basis for agreements among network providers, and between end users and their network providers. Appendix I provides information about how asynchronous transfer mode (ATM) might support IP laye
9、r performance. Appendix II discusses alternatives for defining IP delay variation. Appendix III presents the hypothetical reference paths (HRP) against which the ITU-T Y.1541 QoS objectives were tested for feasibility. Appendix IV gives example computations of packet delay variation. Appendix V disc
10、usses issues that must be considered whenever IP measurements are made. Appendix VI describes the relationship between this Recommendation and the IETF-defined mechanisms for managing QoS. Appendix VII gives estimates of speech transmission quality for the hypothetical reference paths of Appendix II
11、I. Appendix VIII discusses digital television transport on IP networks. Appendix IX estimates transmission control protocol (TCP) file transfer performance on paths conforming to ITU-T Y.1541 objectives. Appendix X gives example calculations for combining delay variation measurements from multiple s
12、ections to estimate user network interface to user network interface (UNI-UNI) performance, and Appendix XI estimates the packet loss requirement for digital circuit emulation. History Edition Recommendation Approval Study Group 1.0 ITU-T Y.1541 2002-05-07 13 1.1 ITU-T Y.1541 App.X 2002-11-08 13 1.2
13、 ITU-T Y.1541 (2002) Amd. 1 2003-08-01 13 1.3 ITU-T Y.1541 (2002) Amd. 2 2004-02-12 13 2.0 ITU-T Y.1541 2006-02-22 12 2.1 ITU-T Y.1541 (2006) Amd. 1 2006-06-13 12 2.2 ITU-T Y.1541 (2006) Amd. 2 2007-01-25 12 2.3 ITU-T Y.1541 (2006) Amd. 3 2008-05-30 12 3.0 ITU-T Y.1541 2011-12-14 12 ii Rec. ITU-T Y.
14、1541 (12/2011) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is respo
15、nsible 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 Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the I
16、TU-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 technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborati
17、ve 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 with this Recommendation is voluntary. However, the Recommendation may contain certain man
18、datory 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 obligatory language such as “must“ and the negative equivalents are used to express requirements.
19、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 this Recommendation may involve the use of a claimed Intellectual Property Right. ITU ta
20、kes 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 date of approval of this Recommendation, ITU had received notice of intellectual property
21、, 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 consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2012 All rights reserved. No
22、 part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T Y.1541 (12/2011) iii Table of Contents Page 1 Introduction and Scope . 1 1.1 Introduction 1 1.2 Scope 2 2 References 3 3 Abbreviations, acronyms and conventions . 3 3.1 Abbre
23、viations and acronyms 3 3.2 Conventions 5 4 Transfer capacity, capacity agreements, and the applicability of QoS classes 6 5 Network performance objectives 6 5.1 General discussion of QoS . 7 5.2 Reference path for UNI to UNI QoS 7 5.3 Network QoS classes 8 6 Availability objectives 14 7 Achievement
24、 of the performance objectives 14 8 Concatenating network sections and their QoS values. 14 8.1 Introduction 14 8.2 Composing UNI-UNI values 15 8.3 Impairment accumulation procedures 16 9 Security . 17 Appendix I ATM network QoS support of IP QoS 18 Appendix II IP delay variation parameter definitio
25、n considerations 19 Appendix III Example hypothetical reference paths for validating the IP performance objectives 21 III.1 Number IP nodes in the HRP . 21 III.2 Example computations to support end-end class 0 and class 1 delay 23 III.3 Example end-end class 1 delay computation . 24 III.4 Example co
26、mputations to support end-end class 4 delay . 25 III.5 Loading within the HRP . 26 III.6 Geostationary satellites within the HRP. 26 Appendix IV Example calculations of IP packet delay variation . 27 IV.1 Contributors to IP packet delay variation . 27 IV.2 Models and calculation procedures to establ
27、ish an upper bound to the IPDV. 27 IV.3 Calculation examples . 29 Appendix V Material relevant to IP performance measurement methods 32 Appendix VI Applicability of the Y.1221 transfer capabilities and IETF differentiated services to IP QoS classes 33 iv Rec. ITU-T Y.1541 (12/2011) Page Appendix VII
28、 Effects of network QoS on end-to-end speech transmission performance as perceived by the user 34 VII.1 Example VoIP calculations with ITU-T Y.1541 class 0 network performance 34 VII.2 Example VoIP calculations with ITU-T Y.1541 class 1 network performance 35 VII.3 Speech quality calculations for IT
29、U-T Y.1541 hypothetical reference paths 35 Appendix VIII Effects of IP network performance on digital television transmission QoS 38 VIII.1 Introduction 38 VIII.2 Hypothetical reference endpoint (HRE) for high-bandwidth video signals . 38 VIII.3 Service profiles and end-to-end packet performance req
30、uirements . 38 VIII.4 Forward error correction (FEC)/Interleaving to improve UNI-UNI performance 40 VIII.5 Laboratory assessment of forward error correction (FEC)/Interleaving effectiveness . 41 VIII.6 Additional performance parameters . 41 VIII.7 Further analysis with advanced FEC schemes . 41 VIII
31、.8 Analysis of retransmission schemes . 42 VIII.9 Recovery from errors and losses due to protection switching schemes . 42 Appendix IX Effects of network QoS on end-to-end data transmission performance using TCP . 43 IX.1 Introduction 43 IX.2 Model of TCP performance 43 IX.3 TCP hypothetical referen
32、ce endpoint (HRE) . 44 IX.4 Observations . 44 IX.5 Summary of TCP capacity estimates . 46 Appendix X An example showing how to calculate IPDV across multiple sections . 47 X.1 Calculation of delay variation 47 X.2 Mathematical background 49 X.3 Special cases . 50 X.4 Estimating skewness from quantil
33、es 51 Appendix XI Digital circuit (ISDN) emulation requirements on IP-based networks . 52 XI.1 Introduction 52 XI.2 Packetization and transport assumptions 52 XI.3 Range of packet loss requirements . 52 XI.4 Effect of forward error correction 53 Bibliography 55 Rec. ITU-T Y.1541 (12/2011) 1 Recommen
34、dation ITU-T Y.1541 Network performance objectives for IP-based services 1 Introduction and Scope 1.1 Introduction Customers require network performance levels that, when combined with their hosts, terminals, and other devices, satisfactorily support their applications. The adoption of IP-based netw
35、ork services IETF RFC 791 has not changed this fact, except that networks must be constrained in terms of packet transfer performance parameters (as defined in ITU-T Y.1540). Traditional application performance requirements are well-understood, but several key contributors are often beyond the netwo
36、rk service providers control (e.g., home networks, LAN, application gateways, terminals, hosts, and other customer devices). We note that objectives on the performance of customer equipment are available, such as ITU-T P.1010 for VoIP terminals and gateways, and combining these objectives with speci
37、fic network performance levels (as appendices of this Recommendation illustrate), a view of application performance can be directly related to network performance. In response, service providers have agreed on network performance levels that they will work together to meet, and have codified the num
38、erical objectives in this Recommendation. Agreement on levels of network performance is highly beneficial, because it constrains a critical and often dominating factor in application performance ITU-T I.350. The objectives are organized in sets called network quality of service (QoS) classes (in Tab
39、le 1) that can be matched with well-designed customer equipment to satisfactorily support various applications (as indicated in Table 2). Classes with provisional objectives are found in Table 3. The number of classes has been deliberately kept small to simplify the engineering of paths traversing m
40、ultiple operators networks, so the objectives in each class must satisfy the needs of multiple applications. Readers of this Recommendation should plan for at least eight classes when considering protocol fields and values, since future expansion of the classes is possible. The objective values resu
41、lt from analysis of key applications such as conversational telephony, multimedia conferencing, reliable data exchange using TCP, and digital television, in concert with network feasibility analysis. The appendices provide significant, detailed testimony as to how the objectives in the network QoS c
42、lasses can be used to determine the end-to-end (application) quality provided. Another factor in the development of objective values has been network feasibility. When paths span wide geographical distances, very long propagation times will prevent low delay objectives from being met, thus additiona
43、l classes are required to address these cases. It is important to clarify how designers of new applications should make use of the ITU-T Y.1541 classes. Designers should consider the packet performance objectives as representative of well-managed IP-based networks and include mitigations for these i
44、mpairment levels in their designs. Only after application requirements have been carefully rationalized and a range of impairment mitigations have been examined, should new QoS classes be considered to address unmet requirements. The network QoS classes form an important link in the chain of develop
45、ments required to assure end-to-end performance. They are part of the lexicon for QoS negotiation among users and networks, especially when signalling protocols communicate QoS requests on a dynamic basis. 2 Rec. ITU-T Y.1541 (12/2011) Verification that the service meets network objectives is anothe
46、r key area of customer interest. This has been addressed here through recommended evaluation intervals, packet payload sizes, and other aspects useful to measurement designers. In addition, the UNI-UNI objectives are directly verifiable by users, in contrast with objectives that apply to non-user in
47、terfaces or utilize information unknown to customers, such as route distance. 1.2 Scope This Recommendation specifies network (UNI-UNI) IP performance values for each of the performance parameters defined in ITU-T Y.1540. The specific performance values vary, depending on the network QoS class. This
48、 Recommendation defines eight network QoS classes, two of which are provisional. This Recommendation applies to international IP network paths (UNI-UNI). The network QoS classes defined here are intended to be the basis of agreements between end-users and network service providers, and between servi
49、ce providers. The classes should continue to be used when static agreements give way to dynamic requests supported by QoS specification protocols. The QoS classes defined here support an extremely wide range of applications, including the following: conversational telephony, multimedia conferencing, digital video, and interactive data transfer. Designers of new user applications should first consider using the existing QoS classes, and possibly include technologies to mitigate packet transfer
