Computer Networking: Internet Protocols in Action

Chapter 2.1. Under the Hood of HTTP

INTRODUCTION

You are probably familiar with HTTP if only because it is the beginning of most URLs like http://www.foo.com. HTTP stands for the Hypertext Transfer Protocol and it is an application layer protocol responsible for the majority of the traffic traversing Internet backbone links.

Application layer protocols are used for communication between computer programs or applications. Typically, the client application sends request messages to a server application and the server application sends back response messages. Application layer protocols rely on the lower layers of the network protocol stack to handle the details of delivering the message over the network. In the case of HTTP, a web browser is typically the client and a web server is typically the server.

Figure 2.1.1. HTTP Request and Response

When you enter a URL in your web browser or click on a hyperlink, your web browser sends an HTTP request over the network to the web server specified in the URL. For example, if you enter the URL http://www.ethereal.com/introduction.html, your web browser will send a message to the machine www.ethereal.com requesting the file introduction.html. In this example, your web browser program is an HTTP client and the web server program running on the machine www.ethereal.com is the HTTP server.

Hypertext Transfer Protocol as its name suggests was defined ...