The software bells and whistles for the World Wide Web (WWW) didn't actually surface until 1991. Scientists at the CERN research laboratory developed the Hypertext Markup Language (HTML) so that they could exchange information about their projects over their TCP/IP network.
HTML is the file format used to create documents that can then be read by a Web browser such as Microsoft Internet Explorer or Netscape Navigator. HTML consists of tags that are used to format a document so that it can be viewed in a Web browser. HTML offers a rich environment for creating documents that can include graphics, sound, video, and links to other HTML documents, such as other Web sites.
Hypertext Transport Protocol (HTTP) is the TCP/IP stack member that provides the connection between an HTTP client (a computer outfitted with a Web browser) and server (which would be a Web server, in this case). A Web client sends a connection-oriented request using HTTP, which uses TCP for the connection, to a particular Web server, typically using the Uniform Resource Locator (URL) for the Web server, which is the DNS name of the server. To make a long story short, the URL is the name that you type into your browser address window. DNS handles the resolution of the URL to an IP address.
The Web server holding the HTML documents or Web site requested by the Web client will respond to the client with a connectionless HTTP communication that uses UDP at the Transport layer of the OSI model. This allows the Web client to access the actual Web site.
I think just about everyone is familiar with the different Web browsers ( clients ) available. As far as Web servers go, in the Unix/Linux world, the Apache Web server is quite popular. Netscape offers the Netscape Enterprise server, which can run on Windows, Linux, and Unix operating systems. Microsoft bundles Internet Information Server with Windows Server 2003 and Windows 2000 Server.
Your choice of Web server software will depend on the NOS you run on your Web server. We will take a look at hosting a Web site in Chapter 16, "Hosting a Web Site."