ITU-T G 1031-2014 QoE factors in web-browsing (Study Group 12)《网页浏览体验质量因素》.pdf

1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T G.1031 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (02/2014) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Multimedia Quality of Service and performance Generic and user-related aspects QoE fact

2、ors in web-browsing Recommendation ITU-T G.1031 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS G.200G.299 INDIVIDUAL CH

3、ARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES G.300G.399 GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES G.400G.449 COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY G.450G.499 T

4、RANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED ASPECTS G.1000G.1999 TRANSMISSION MEDIA CHARA

5、CTERISTICS G.6000G.6999 DATA OVER TRANSPORT GENERIC ASPECTS G.7000G.7999 PACKET OVER TRANSPORT ASPECTS G.8000G.8999 ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.1031 (02/2014) i Recommendation ITU-T G.1031 QoE factors in web-browsi

6、ng Summary Recommendation ITU-T G.1031 describes the framework for an opinion model for web-browsing quality of experience (QoE). User perceived quality for web-browsing is dependent on various influence factors (IF) that are related to user, context and system. This Recommendation addresses the lat

7、ter two influence factors (context and system) and provides an overview of them. At the perceptual level, it defines the relevant events that the user perceives while accessing a web page and contrasts them with the events taking place at the application level and at the network level. History Editi

8、on Recommendation Approval Study Group Unique ID* 1.0 ITU-T G.1031 2014-02-13 12 11.1002/1000/12123 Keywords Modeling, page-view cycle, perceptual events, web-browsing session, web-QoE. _ * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, fol

9、lowed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T G.1031 (02/2014) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technolo

10、gies (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 telecommunications on a worldwide basis. The World Telecommu

11、nication 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 the procedure laid down in WTSA Resolution 1. In some areas

12、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 both a telecommunication administration and a recognized operat

13、ing 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 all of these mandatory provisions are met. The words “shall“

14、 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 RIGHTSITU draws attention to the possibility that the practi

15、ce 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 developm

16、ent 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 this may not represent the latest information and are therefore

17、 strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2014 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 G.1031 (02/2014) iii Table of Contents Page 1 Scope . 1 2

18、References . 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Recommendation . 1 4 Abbreviations and acronyms 1 5 Conventions 2 6 Factors influencing web-QoE . 2 6.1 Context influence factors 2 6.2 System influence factors . 3 7 Perceptual dimension 4 8 Use cases of a web-Qo

19、E opinion model . 4 Bibliography. 6 Rec. ITU-T G.1031 (02/2014) 1 Recommendation ITU-T G.1031 QoE factors in web-browsing 1 Scope This Recommendation describes the framework for an opinion model for web-browsing QoE. This Recommendation aims to provide: guidance in the development of an opinion mode

20、l an overview of key influence factors (IF) a starting point for performance assessment and KPI definitions. This Recommendation introduces a taxonomy of influence factors and related model parameters, as well as a definition of QoE relevant perceptual events. 2 References This Recommendation does n

21、ot use any normative references. 3 Definitions 3.1 Terms defined elsewhere None. 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 element: Visual content of a webpage, which is displayed to the user on the rendered webpage, e.g., text, pictures, widgets

22、, videos, etc. 3.2.2 first element: A character or a picture for example. 3.2.3 object: A HTTP object that is used for processing and rendering the webpage and is referenced by the page mark-up or script. An object however is not necessarily visible on the fully rendered page (see the definition for

23、 element). 3.2.4 visible portion: The part of the requested web page that is visible to the user. 3.2.5 web-browsing session: A web-browsing session is an interactive information exchange between a user and one or more websites over a limited period of time, mediated via a web-browsing application.

24、The starting point of such a session is the first page request initiated by the user, which is followed by a number of requestresponse interactions between the user and the webhost(s), resulting in a series of page views b-Egger1. A web session is typically terminated when the user exits the browsin

25、g application or stops the browsing activity for a certain period of time. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: CPU Central Processing Unit HTML Hyper Text Mark-up Language IF Influence Factor OS Operating System 2 Rec. ITU-T G.1031 (02/2014

26、) PLT Page Load Time QoE Quality of Experience RTT Round Trip Time 5 Conventions This Recommendation uses the following notation: t0: The moment in time when the user requests a new web page (typically by clicking or pressing enter “Enter“ after having typed the URL of the web page in the browsers a

27、ddress bar). tSBr: The moment in time when a change in the status bar happens (usually a progress bar becomes visible at this moment). tSgB: The moment in time when the previously viewed web page vanishes and the content of the requested page has not yet started to render. tPrs: The moment in time w

28、hen the first element of the requested page appears on the screen, independent of the type of element. tPPLT: The moment in time when from the point of view of the user the page is sufficiently rendered such that he can access the information he is looking for. tVSrc: The moment of time when the vis

29、ible portion of the web page (as determined by screen or browser windows size) is fully rendered1. tIHRs: The moment in time when the initial HTTP request is sent by the browser. tBHPr: The moment in time when the first HTML element is received (see b-W3schools). tHp: The moment in time when the HTM

30、L page is processed by the browser (can only be observed at application level). tTPLT_1: The moment of time when all objects of the page are downloaded from the server at the browsers device. tTPLT_2: The moment of time when the page is completely rendered and displayed by the browser. 6 Factors inf

31、luencing web-QoE Typically, QoE influence factors (IFs) are grouped according to the following three main categories: User influence factors Context influence factors System influence factors User influence factors are outside of the scope of this Recommendation. Context influence factors are discus

32、sed in clause 6.1. System influence factors are discussed in clause 6.2. 6.1 Context influence factors The context in which a web page is accessed can have a critical influence on the user behaviour and his QoE. The range of context influence factors spans: Location: Cafeteria, office, home _ 1 It s

33、hould be noted that there can be further rendering activity outside of the visible screen area. Rec. ITU-T G.1031 (02/2014) 3 Interactivity: High level interactivity vs. low level interactivity Task type: business, entertainment, etc. Task urgency: urgent vs. casual (without time constraints). 6.2 S

34、ystem influence factors The range of system influence factors spans the following content, network and client related IFs: Server-related influence factors (see clause 6.2.1) Content-related influence factors (see clause 6.2.2) Delivery network influence factors (see clause 6.2.3) Client influence f

35、actors (see clause 6.2.4) In order to better understand the position of these IFs in the delivery chain, a typical Web-QoE delivery chain is depicted in Figure 1. G . 1 0 3 1 (1 4 )_ F 0 1P er ce i v ed q u al i t yU s erD ev i ceA cc es s n et w o rk C o re n et w o rk In t er n etP ro d u ce d q u

36、 al i t yS er v er + co n t en tFigure 1 Delivery chain for a typical webpage 6.2.1 Server-related influence factors Response time (determined by CPU, OS, memory, software, etc.) Capacity of the link(s) connecting the server(s) and the Internet. 6.2.2 Content-related influence factors These factors

37、go beyond the established notion of content as used in QoE. This is because in Web QoE, content is typically constituted by a mix of different element types such as text, pictures, audio files and videos. In addition, the HTML mark-up of the webpage (and related scripts) strongly determines the actu

38、al loading behaviour of the page according to its internal structure and the utilized objects such as: Number of objects Type of objects Size of objects Order of objects Number of elements Type of elements Size of elements Element appearance on the screen (determined by the order of the objects as w

39、ell as by the rendering strategy of the browser, see b-Strohmeier). 6.2.3 Delivery network influence factors Network contribution to transaction time (see b-ITU-T G.1040) Available capacity (see b-ITU-T Y.1540) Caching along the delivery network: The caching elements lower perceived server response

40、time as they shorten client-to-server requests and therefore lower the RTT. 4 Rec. ITU-T G.1031 (02/2014) 6.2.4 Client influence factors Resource (webpage) loading procedure Processing power and other processes demanding processing power Browser implementation TCP/IP stack and configuration Operatin

41、g system. All of these IFs impact the user perceived performance of the web page display when requested by the user. 7 Perceptual dimension When the end user requests a page by means of entering a dedicated web address or clicking on a link on an already loaded web page, the download of content from

42、 a web server is initiated. This requested content (typically a base HTML page that references additional elements like images and scripts) is progressively fetched and rendered by the browser. During this process the user encounters several observable events as depicted in Figure 2. Figure 2 Percep

43、tual events in a web page view cycle from the end-user point of view Note that in this figure the application and network timeline (in blue) displays related technical events at the application or network levels. Note also that in this figure the distance between the perceptual events is shown as be

44、ing equal, but this is not necessarily the case in real-world browser implementations. This description differentiates between perceived page load time (PLT) tPPLT and technical page load time tTPLT_1 (or tTPLT_2 depending on the actual measurement procedure). This differentiation is important since

45、 ultimately, for the user QoE, only the perceived PLT tPPLT matters. This distinguishes this description from related work described in Annex A of b-ITU-T G.1030, where only the technical PLT tTPLT is used as a basis for QoE estimation. This difference is essential, since tPPLT can be considerably s

46、horter than tTPLT and depends on several technical and non-technical influence factors such as user task, web page design, number of elements, etc. This is shown in b- Egger2 where the presented empirical data from subjective tests quantifies the differences between these two points in time. NOTE In

47、 a regular web-browsing session the end user encounters several sets of such page view event sequences. 8 Use cases of a web-QoE opinion model A perceptual opinion model for Web-QoE can be used in the following use cases: Network dimensioning, including: Network planning Rec. ITU-T G.1031 (02/2014)

48、5 Traffic management solutions design and optimization Online/offline measurement of Web-QoE based on network and application logs or probes Performance testing (of elements in the delivery chain). 6 Rec. ITU-T G.1031 (02/2014) Bibliography b-ITU-T G.1030 Recommendation ITU-T G.1030 (2014), Estimati

49、ng end-to-end performance in IP networks for data applications. b-ITU-T G.1040 Recommendation ITU-T G.1040 (2006), Network contribution to transaction time. b-ITU-T Y.1540 Recommendation ITU-T Y.1540 (2011), Internet protocol data communication service IP packet transfer and availability performance parameters. b-Egger1 Egger, et al., “Waiting times in quality of experience for web based services,“ In Proc.