ITU-T G 1000-2001 Communications Quality of Service A Framework and Definitions Series G Transmission Systems and Media Digital Systems and Networks Quality of Service and Performa.pdf

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1、INTERNATIONAL TELECOMMU N KATION U NION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU SERIES G: TRANSMISSION SYSTEMS AND DIGITAL SYSTEMS AND NETWORKS GA000 Quality of service and performance (1 1/2001) MEDIA, Communications quality of service: A framework and definitions ITU-T Recommendation

2、 G. 1 O00 INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU GA000 (1 1/2001) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Quality of service and performance Communications quality of service: A framework and definitions ITU-T Recomm

3、endation G. 1 O00 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER- TRANSMISSION SYSTEMS INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SY

4、STEMS ON METALLIC LINES GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE METALLIC LINES SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY TESTING EQUIPMENTS TRANSMISSION MEDIA CHARACTERISTICS DIGITAL TERMINAL EQUIPMENTS DIG

5、ITAL NETWORKS DIGITAL SECTIONS AND DIGITAL LINE SYSTEM QUALITY OF SERVICE AND PERFORMANCE TRANSMISSION MEDIA CHARACTERISCTICS DIGITAL TERMINAL EQUIPMENTS G. 100-4.199 G.200-G.299 G.300-G.399 G.400-G.449 G.450-G.499 G.500-G.599 G.600-G.699 G.800-G.899 G.1000-G.1999 G.6000-G.6999 G.7000-G.7999 G.700-G

6、.799 G.900-G.999 For further details, please refer to the list of ITU-T Recommendations. ITU-T Recommendation G.lOOO Communications quality of service: A framework and definitions Summary This Recommendation gives a fiamework and definitions for communications quality of service so as to establish a

7、 uniform approach to quality of service across the ITU-T and eliminate the confusion resulting fi-om different frameworks and inconsistent definitions. Improved consistency regarding quality of service is needed throughout the communications industry, especially in IP-related areas within and outsid

8、e the ITU. This Recommendation provides a practical “top-down“ path from a general quality definition (IS0 8402) to a QoS definition (ITU-T Rec. E.800) to network performance (ITU-T Rec. 1.350, and Y.1540) to a functional breakdown of all components of service quality (the QoS definition matrix of E

9、TSI ETR 003). Additionally presented are four viewpoints of QoS that make the definitions and framework meaningful for everyone: users, vendors, network operators, service providers, etc. This overall approach is believed to be highly useful because it encourages a consistent and uniform mapping bet

10、ween the top-down, framework definitions of QoS and the bottom-up, operational measures on network elements. Advantages of using this approach is that it not only helps identify QoS-related problems, but it also facilitates quantifying the problem from multiple views; the customers (e.g. surveys and

11、 subjective tests) and the service providers (network measurements). This helps assure that resolving the problem in one domain (e.g. the provider) also resolves it in the other (e.g. the customer). Source ITU-T Recommendation G. 1 O00 was prepared by ITU-T Study Group 12 (200 1-2004) and approved u

12、nder the WTSA Resolution 1 procedure on 29 November 2001. ITU-T Rec. G.lOOO (11/2001) i FOREWORD The International 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

13、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 Standardization Assembly (WTSA), which meets every four years, establishes the top

14、ics 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 technology which fall within ITU-Ts purview, the necessary standards are pre

15、pared on a collaborative basis with IS0 and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the pr

16、actice 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 ITU members or others outside of the Recommendation deve

17、lopment 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, implementors are cautioned that this may not represent the latest information and are there

18、fore strongly urged to consult the TSB patent database. O ITU 2002 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. 11 ITU-T Rec. G.1000 (11/2001) CONTENTS Page 1 2 3 4 5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 6 Scope . Re

19、ferences Definitions Abbreviations and Acronyms . Communications Quality of Service: A framework and approach . An elaboration on definitions for Quality and Quality of Service A framework for the quality of communications services Matrix for the determination of communications QoS criteria . Relati

20、onship between QoS and Network performance . Four viewpoints of QoS 5.5.1 5.5.2 5.5.3 5.5.4 Relationship between the four viewpoints of QoS . Customers requirements of QoS . QoS offered by the service provider QoS achieved or delivered by the service provider . QoS perceived by the customer . The Ch

21、allenge of IP-related QoS Conclusion Appendix I . Bibliography 1 1 1 2 2 2 2 3 4 6 7 . ITU-T Rec . G.1000 (11/2001) 111 ITU-T Recommendation G.1000 Communications quality of service: A framework and definitions 1 Scope This Recommendation addresses the need for a consistent approach to QoS, with a g

22、oal of setting a well-defined and relevant (e.g. customer-affecting) approach that can be readily used to plan and deploy networks, and to monitor service quality. Improved consistency regarding QoS is needed throughout the communications industry, especially in IP-related areas. While there is an u

23、rgent need in the industry for more consistency and uniformity in QoS as it applies to IP-related networks and services, the QoS framework and approach presented here can be applied to all communications services, such as mobile, wireline, multimedia, etc. 2 References The following ITU-T Recommenda

24、tions 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 this Recommendation are theref

25、ore 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 published regularly. NOTE-The reference to a document within this Recommendation does not give it, as a s

26、tand-alone document, the status of a Recommendation. - ETSI ETR 003 ed.2 (1994), Network Aspects (NA); General Aspects of Quality of Service (QoS) and Network Performance (NP). IS0 8402: 1994, Quality management and quality assurance - Vocabulary. IS0 9000:2000, Quality management systems - Fundamen

27、tals and vocabulary. ITU-T Recommendation E.800 (1 994), Terms and de3nitions related to quality of service and network performance including dependability. ITU-T Recommendation G. 1 O 1 O (2001), End-user multimedia QoS categories. ITU-T Recommendation 1.350 (1993), General aspects of quality of se

28、rvice and network performance in digital networks, including ISDN. ITU-T Recommendation Y. 1540 (1 999), Internet protocol data communication service - IP packet transfer and availability performance parameters. - - - - - - 3 Definitions This Recommendation defines the following terms: 3.1 implied n

29、eeds (IS0 8402). 3.2 degree of satisfaction of a user of the service (ITU-T Rec. E.800). 3.3 applications of customershsers of a service, which may be expressed non-technically. quality: the totality of characteristics of an entity that bear on its ability to satisfy stated and quality of service (Q

30、oS): the collective effect of service performances, which determine the QoS requirements of userkustomer: a statement of the level of quality required by the ITU-T Rec. G.lOOO (11/2001) 1 3.4 to the customer by the service provider. 3.5 achieved and delivered to the customer. 3.6 believe they have e

31、xperienced. QoS offered/planned by provider: a statement of the level of quality expected to be offered QoS delivered/achieved by provider: a statement of the level of the actual quality QoS perceived by user/customer: is a statement expressing the level of quality that customers 4 Abbreviations and

32、 Acronyms ETSI FITCE IETF IP IS0 ITU-T NI NP QOS SLA 5 5.1 This Recommendation uses the following abbreviations: European Telecommunications Standards Institute Federation of Telecommunications Engineers of the European Community (Fdration des ingnieurs et experts des tlcommunications de la Communau

33、t Europenne) Internet Engineering Task Force Internet Protocol International Organization for Standardization International Telecommunication Union - Telecommunication Standardization Sector Network Interface Network Performance Quality of Service Service Level Agreement Communications Quality of Se

34、rvice: A framework and approach An elaboration on definitions for Quality and Quality of Service The term quality of service (QoS) is extensively used today, not just in the telecommunications world in which it has its roots, but increasingly regarding broadband, wireless and multimedia services tha

35、t are IP-based. Networks and systems are gradually being designed in consideration of end-to-end performance required by user applications; however, the term QoS is usually not well- defined, is used loosely, or worst of all, misused. In looking for candidate definitions of quality and QoS, IS0 8402

36、 provides a general definition of quality itself, whereas ITU-T Rec. E.800 provides a definition of QoS: As noted, a definition of general quality is provided in IS0 8402 as “the totality of characteristics of an entity that bear on its ability to satis - - QoS achieved or delivered; - For any frame

37、work of QoS to be truly useful and practical enough to be used across the industry, it must be meaningful from these four viewpoints, which are illustrated in Figure 2 and defined thereafter. While Figure 2 shows the “top down“ relationship of these viewpoints, it does not indicate how, for example,

38、 QoS actually gets implemented by the service provider. This requires many detailed methods done in a more “bottom up“ operation that is not addressed in this Recommendation. (The point of this Recommendation is that a single QoS definition and framework can support all of the viewpoints of Figure 2

39、.) Service providers offerings of QoS (or plannedtargeted QoS); Customer survey ratings of QoS. CUSTOMER SERVICE PROVIDER T1213040-OZ Figure 2/G.1000 - The four viewpoints of QoS 4 ITU-T Rec. G.lOOO (11/2001) 5.5.1 Customers requirements of QoS QoS requirements by the customer state the level of qua

40、lity required of a particular service, which may be expressed in non-technical language. The customer is not concerned with how a particular service is provided, or with any aspects of the networks internal design, but only with the resulting end-to-end service quality. From the customers point of v

41、iew, quality of service is expressed by parameters, which: - - - - - focus on user-perceived effects, rather than their causes within the network; do not depend, in their definition, on assumptions about the internal design of the network; take into account all aspects of the service from the custom

42、ers point of view; may be assured to a user by the service providers, sometimes in contractual terms; are described in network-independent terms and create a common language understandable by both the user and the service provider. Of special interest is ITU-T Rec. G.lO1O on the QoS requirements of

43、end users for all their applications. This Recommendation explicitly addresses the “customer requirement“ viewpoint, which can be used by the service provider to plan the network service level. 5.5.2 QoS offered by the service provider is a statement of the level of quality expected to be offered to

44、 the customer by the service provider. The level of quality is expressed by values assigned to QoS parameters. The principal use of this form of QoS is for planning and for Service Level Agreements. Each service would have its own set of QoS parameters (as in the QoS Classes of ITU-T Rec. Y.1540 for

45、 IP service offers). The service provider may express the offered QoS in non-technical terms for the benefit of customers, and in technical terms for use within the business. QoS offered by the service provider can be used in planning documents, to specify measurement systems and also can be used to

46、 form the basis of the SLAs. For example, a service provider may state, for the benefit of customers, that the availability of basic telephony service is planned to be 99.95% in a year with not more than a 15-minute break at any one occasion, and not more than 3 breaks over the year. QoS offered by

47、the service provider 5.5.3 QoS achieved by the service provider is a statement of the level of quality actually achieved and delivered to the customer. This is expressed by values assigned to parameters, which should be the same as specified for the offered QoS so that the two can be compared to det

48、ermine what was actually achieved to assess the level of performance achieved. These performance figures are summarised for specified periods of time, e.g. for the previous month. For example, the service provider may state that the achieved availability for the previous quarter was 99.95% with five

49、 breaks of service of which one lasted 65 minutes. The QoS achieved or delivered is used by the industry, sometimes by regulators, for publication in the interests of customers. QoS achieved or delivered by the service provider 5.5.4 QoS perceived by the users or customers is a statement expressing the level of quality experienced they believe they have experienced. The Perceived QoS is expressed, usually in terms of degrees of satisfaction and not in technical terms. Perceived QoS is assessed by customer surveys and from customers own comments on levels of service. Per