5. Compute the time it takes from when the user clicks on a hot link in their br

Question

5. Compute the time it takes from when the user clicks on a hot link in their browser to the time the web page appears. a. Assume the following i. All DNS caches are full, and so no DNS lookup is necessary ii. The URL of the base page is http://www.cnn.com/. The base page fits in one packet iii. The base page contains two objects, each object is stored on a different server. iv. The URL to the first object is http://pics.cnn.com/logo.jpeg. v. The URL to the second object is http://www.google.com/pic.jpeg vi. Each object fits into one packet. vii. The RTT to cnn.com servers is RTTc viii. The RTT to google.com servers is RTTg ix. All links are very high data rate, so transmission time can be ignored. b. Draw a timing diagram that shows the web transaction. On the diagram, provide details about the transport layer packets and application layer packets (if any). c. Compute the time from when the user clicks on the hot link until the base-file is receiver d. Assume that parallel connections are used to download the objects. What is the time to download the objects? e. What is the time to download the complete web page? f. Would the time to get the web page change if persistent HTTP was used? (Feel free to use power point or some drawing app. Either paste your diagram here or zip this doc and your ppt file together)

Explanation / Answer

HTTP with Non-Persistent Connections

Let’s walk through the steps of transferring a web page from server to client for the case of non-persistent connections. Let’s suppose the page consists of a base HTML file and 10 JPEG images, and that all 11 of these objects reside on the same server. Further suppose the URL for the HTML file is.

As the browser receives the web page, it displays the page to the user. Two different browsers interpret (that is, display to the user) a web page in somewhat different ways. HTTP has nothing to do with how a Web page is interpreted by a client. The HTTP specifications ([RFC 1945] and [RFC 2616]) define only the communication protocol between the client HTTP program and the server HTTP program.

HTTP persistent connection, also called HTTP keep-alive, or HTTP connection reuse, is the idea of using a single TCP connection to send and receive multiple HTTP requests/responses, as opposed to opening a new connection for every single request/response pair. The newer HTTP/2 protocol uses the same idea and takes it further to allow multiple concurrent requests/responses to be multiplexed over a single connection.

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