Since majority of our test applications are
based on web protocols, we are going to see how a web request works in this
post.
What happens when we type the
URL and click Enter in address bar:
Say that we are typing a URL in the address bar
“http://www.google.com/performancetesting.htm”.
This URL has three parts:
1. Protocol (http://)
2. Domain Name (www.google.com)
3. File name (“performancetesting.htm”)
- Browser communicates with Domain Name
Server (DNS) to convert the domain name (google.com) into IP address.
- Then with the IP address, it makes a
connection with web server on port 80(default port for Webserver). Ideally
this will be the ip address of a load balancer that manages a cluster of
web servers.
- Browser then sends a HTTP (GET request in
this case) asking for the content of the required file
“performancetesting” .
- If the server cannot find the requested
page, it will send an HTTP 404 error message. (404 means 'Page Not Found'
as anyone who has surfed the web will probably know).
- The web browser receives the page back and
the connection is closed.
- The browser then parses through the page
and looks for other page elements it needs to complete the web page. These
usually include images, applets, etc.
- For each element needed, the browser makes
additional connections and HTTP requests to the server for each element.
- When the browser has finished loading all
images, applets, etc. the page will be completely loaded in the browser
window.
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