Web Page Design: How it Works 01

Now it's time to put this all together.

If you popup this schematic as you read along, we'll go through the things that occur when you browse a web page.

  1. Let's suppose you want to see a web page "http://www.iwantit.com/home.html". First you dial up your local ISP and connect to the Internet. Your ISP will give you a temporary IP address to use on your PPP connection from its pool of available addresses. For the time you are connected, your computer is a host on the Internet and can use all the Internet resources and protocols.
  2. You start up your browser and type in the URL: http://www.iwantit.com/home.html. The browser needs to find the IP address for www.iwantit.com so it asks the DNS server in its configuration for the IP address.
  3. When it gets the IP address, it asks that host for the file "/home.html" via the HTTP protocol.
  4. The host www.iwantit.com finds that page, determines its MIME type and sends the file back to the browser in an HTTP response packet with error codes and data. Then it logs the connection event.
  5. The browser parses the HTML and finds the other resources needed for the page, such as images and embedded applications. The browser will cache the file locally in case you view it again and log the history event.
  6. The browser sends additional HTTP requests for each of the page resources, perhaps in several parallel connections, while it is rendering the web page for you. These also get cached and logged locally.
  7. As data is returned from Internet hosts in HTTP responses, the browser reads the MIME types and decides what to do with the data. Images get rendered, other data gets sent to appropriate plug-ins and helper applications. Errors are handled by the browser and displayed for you in appropriate way (bad image icons, "404 Not Found", "No DNS entry found", etc.).
  8. If all goes well, you are browsing that web page and its resources!

This is the end of this section.

Go to Contents Copyright 1999 by Jim Hurley. All rights reserved.