Characterizing Home Pages 1

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1 Characterizing Home Pages 1 Xubin He and Qing Yang Dept. of Electrical and Computer Engineering University of Rhode Island Kingston, RI 881, USA Abstract Home pages are very important for any successful web sites because they give users the first look. A good home page attracts more hits, which means more chances for e-business. This paper investigates the home pages of 95 popular web sites given by PC Magazine. We present a broad range of statistics pertaining to these pages, including: page size, embedded object type and size distributions, dynamic references and ad banners, response time, etc. We also examine how a browser downloads the home page and the embedded objects referenced by the page. Our measurements show that the mean size of the home page is 3KB, 83 of the home pages make use of Java scripts, and 8 of them at least have a reference to dynamic objects such as asp, CGI, Servlet or JSP. Only of the home pages have more than embedded objects, and 89 of the embedded objects are image files. The average response time is less than seconds for 9 home pages, while it takes up to seconds to transfer some dynamic ad banners and web cached image files. Key Words WWW, characterization, dynamic object, home page 1. Introduction With the phenomenal growth and popularity of the Internet. To the success of web sites, it is becoming necessary and important to understand the web behavior. Much research has been sparked to measure and evaluate the web, such as web performance evaluation and improvement [1,3,7,8,9], workload characterizations [,6], web capacity measurement [3,,,15,16], user studies [5,13], etc. Arlitt and Williamson [] present a workload characterization study of web servers based on six different web server access logs. Bray [] measures the whole web and gives some statistics on web size, connectivity, richness and distribution of URL links. Manley and Seltzer [] quantify the web based on server log analysis of sites. These research focus on either the web servers or the web as a whole. There is no published research characterizing individual home pages, which are the pages typically encountered first at a World Wide Web site. A home page usually contains links to the other pages of the site or to other sites. Home pages are very important for any successful web sites because they give users the first look. A good home page attracts more hits, which means more chances for e-business. Various home pages have different styles. We suspect that the home page should have some features different from other pages of a web site. This paper investigates the home pages of the 95 popular web sites given by PC Magazine [1]. We present a broad range of statistics pertaining to these pages, including: page size, embedded objects type and size distributions, dynamic objects and ad banners, and response times. 1 This research is supported in part by National Science Foundation under Grants CCR and MIP97137

2 We try to answer the following questions about the home pages: What is the average size of home pages? How many objects (files) are transferred from the server to display a home page on a browser? What data formats are the embedded objects in a home page? How long does it take for a browser to download a home page and its embedded objects? How often does a home page use dynamic features such as asp, CGI, Servlet or JSP? To answer the above questions, we have conducted an extensive investigation of the home pages from 95 realistic web sites. Our measurement results show that the mean size of the home pages is 3KB, 83 of the home pages make use of Java scripts, and 8 of them at least have a reference to dynamic objects such as asp, CGI, Servlet or JSP. Only of the home pages have more than embedded objects, and 89 of the embedded objects are image files. The average response time is less than seconds for 9 home pages while it takes up to seconds to transfer some dynamically generated ad banners and web cached image files. The rest of this paper is organized as follows. Section describes the tool and methodology we used to perform our study. Section 3 discusses the measurement results and we present our concluding remarks in Section.. Tool and Methodology We examined the top web sites given by PC Magazine in April. We found that 5 out of these sites were already out of business. Our following measurements are based on the home pages from the remaining 95 sites. These 95 sites cover categories, including career, instant messaging, computing, family, education, finance, lifestyle, portals, search engine, online shopping, e-business, web development, etc. Our investigation focuses on the home pages and their embedded objects. A home page is the central document (typically HMTL page) of a site, and the embedded objects are the files (mainly image files and style sheets) that are downloaded along with the home page in order to display the home page on the browser. We used WebPerf [1] monitor to perform the data collection. WebPerf is a tool for measuring response time of specified URLs from multiple locations on the Internet. We use the WebPerf s URL breakdown function. According to this function, when we provide a URL, the WebPerf will show what is actually being downloaded, how long it takes to download and sizes of the individual objects. We use WebPerf on the home page URLs of the above sites and collect the data such as objects size, type and time to download. Before each measurement, we cleared the browser cache settings. After collecting the data, we analyzed a variety of properties of the home pages based on the data. 3. Measurement Results After investigating and examining the 95 web sites, we analyzed a variety of properties of these home pages. In this paper we present results on the following: Home Page Document Size, Embedded Objects, Dynamic References and Response Times. Document Size Among the 95 sites, the minimum home page size is.kb; the maximum size is 77KB; the mean size is 3KB and the standard deviation is Figure 1 presents different views of the size distribution.

3 HTML size distribution HTML size distribution Size (KB) 7 7 <1k 1k-k k-k k-k k+ (a) Snapshot of each site (b) Percentage statistic Figure 1: Distribution of home page sizes. Figure 1a covers one snapshot of the tested home pages. Figure 1b shows that all tested home pages are less than KB, and 68 of them fall between KB and KB. Embedded Objects The above document size does not include the size of embedded objects, which are transferred from the server along with the home page. Embedded objects are referenced by the home page documents by <SRC= > tag, and one exception is the external style sheet object (.css), which is referenced by <link HREF= > tag. Embedded objects are different from the inlinks [,16], which are referenced by <a HREF= > tag ~5 6~ 11~15 16~ 1~5 6~ 31~35 36~ 1~5 6~ + Figure : Distribution of embedded object counts. 9 7 gif htm jpg js css other Figure 3: Distribution of embedded object types. Figure shows that all home pages contain at least one embedded object reference. Only of them contain more than objects. Figure 3 shows the data format distribution of the embedded objects by their extensions. Not surprisingly, GIF images are the most popular representing about 83. of the total embedded objects. HTML and JPEG files are about 6 and 5 respectively. JavaScript and style sheet represent around 5 together. All other formats are below 1. From Figure 3, we found that 5 data formats covered 99 of the embedded objects. That means when we visit a home page of a site, on average, about 9 of the downloaded objects are image files (GIF or JPEG). Although JavaScript and style sheet together represent

4 Size (KB) <1k 1k-k k-k k-k k+ (a) (b) Figure : Distribution of embedded object sizes. only 5 of the traffic, further investigation shows that 37 and 83 of all the tested home pages use external style sheet and java script, respectively. Figure and Table 1 present different views of the embedded object size distribution. Figure a gives a snapshot of total size of the embedded objects referenced by each home page. The maximum size of all the embedded objects referenced by a single home page is about 19KB. Figure b shows that 5 home pages contain embedded objects with total size between KB and KB. Only 6 home pages contain objects with total size more than KB. We give the size statistics of all the embedded objects in Table 1. Dynamic References Many techniques are used to generate dynamic pages, such as active server page (ASP), Java server page (JSP), common gateway interface (CGI), Servlet (the server side Applet of Java language), PHP (a server-side, cross-platform, HTML embedded scripting language). Table lists how often the techniques are used in the home pages. Our results show that 8 of the home pages contain at least one reference to start a dynamic object. Where ASP and CGI are the most popular, each at about 7. Servlet and JSP are used at 18 and 16 respectively, and PHP is only used by 3 of the tested home pages, because PHP is a new language compared to others. Table 1: Embedded object size statistics. Type htm jpg gif js css Other Total Min Size Max Size 78k 36k 3k 8k 1.8k 5.76k 78k Median 1k 3.65k.61k.3k 3.7k.8k 1.1k Mean 19.3k 5.5k 1.5k 3.75k 3.68k 1.77k.98k Table : Dynamic references. ASP CGI Servlet JSP PHP Total dynamic references Number of home pages of total

5 Response time Average Overall 1 Time (Seconds) # of objects Figure 5: Time to download the home pages and their embedded objects. Some home pages contain more than one of the above techniques. Further investigation shows that 7 of the home pages contain at least one dynamically generated ad banner. Response Times Our next measurement tries to estimate how a browser downloads a home page and its embedded objects. We define the overall response time of a home page as the time it takes to download the home page itself and all the embedded objects referenced by the home page. The average response time of a home page is defined as the average time it takes to download all the objects referenced by that home page. The overall and average response times for each home page are plotted in Figure 5. We observed that 9 of the average response times were less than seconds. The overall response times vary greatly from one home page to another, from.8 seconds to more than seconds. Figure 5 also shows that there is a big difference between the average response time and overall response time for many home pages, which suggests that some objects could be the bottleneck to be downloaded. To take a insight look, we illustrates the average response times by object types in Figure 6, where ad means dynamically generated ad banners, and p-gif stands for the images downloaded from the web proxy. We called these images web cached images. Figure 6 shows that the home page itself and the referenced style sheet and java script objects can be downloaded within 1.5 seconds on average, while it takes more than 3 seconds to download the dynamically generated ad banners and web cached images on average. time (seconds) css js htm gif jpg ad p-gif Figure 6: Average response time (by object types). To further investigate how the time is spent on downloading the individual objects, we split up the time into parts [1]: Connect Time: the time it takes to actually open up a connection to a web site;

6 DNS Time: the time it takes to resolve the machine name to an IP address; First Byte: the time it takes to start getting a response back from the server after it has received the HTTP request; Transfer: the time it takes to transfer the entire object; p-gif ad jpg gif htm js css Timing components Connect DNS First Byte Transfer 1 3 Time Line (seconds) Figure 7: Timing components. The results are shown in Figure 7. The html files have the shortest connect time while longest DNS time. The reason for the shortest connect time is that we cannot start downloading any embedded objects before the home page itself. We are using HTTP 1.1 protocol which supports persistent connections [11]. Once the connection is established and the machine name to IP address is resolved, the DNS resolution is unnecessary when downloading the embedded objects. That s why the HTML files have the longest DNS time while there are almost no DNS time to download other embedded objects such as css, js, gif files. One exception is for the web cached images. When downloading web cached images, the DNS time is still obvious because these files are downloaded from the proxy server other than the original server. It takes some time to resolve the proxy machine name to an IP address. From Figure 7, we also observed that the embedded objects (such as css and js files) could be received earlier than the original home pages (HTML). This can be explained as follows. A normal web browser actually starts ~ connections to request components of the page, as the browser is receiving parts of the home page it can start requesting the embedded objects as it sees them [1].. Conclusions This paper investigates the home pages of 95 popular web sites. Based on the quantitative analysis, we present a broad range of statistics pertaining to these pages. Our measurements show that the home page has some features different from other pages of a web site. The mean size of home pages is 3KB. More than of them exploit Java scripts and dynamic objects such as ASP, CGI, Servlet JSP and PHP. Only of the home pages have more than embedded objects, and 89 of these objects are image files. We hope our observations are helpful to the home page design and web development. Acknowledgments The authors would like to thank the anonymous reviewers for their constructive comments on the draft, which have led to a much better presentation of this paper. This research is supported in part by National Science Foundation under Grants CCR and MIP Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. References [1] M. Almeida, V. Almeida, and D. J. Yates, Measuring the Behavior of a World-Wide

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