Chapter 6

How Intranet Web Servers and Browsers Work


Without the World Wide Web, there would probably be very few intranets. There are many forces driving corporations to set up an intranet, but the main one is the dominating presence of the World Wide Web. The Web has made it possible for companies to better communicate vital information among employees, departments, and divisions; to better communicate with customers; and to make it easy for those within a company to get at the vast resources often locked up in corporate databases and information centers.

The Web makes it easy to publish information because each Web page allows people to incorporate text, graphics, sound, animation, and other multimedia elements. In essence, each page is an interactive multimedia publication. This means that a company can easily publish simple documents such as personnel handbooks or expense reports. They can also create sophisticated pages that let people do more than just read a corporate annual report, and also let them see videos of the company in action or listen to speeches by corporate officers. The page at the top (or entrance to a site) is called a home page.

The Web is also a powerful intranet tool because of the way it can link corporate home pages to one another. Hypertext links any home page to any other home page, and to graphics, binary files, multimedia files, and any Internet or intranet resource. To jump to one home page from another, you merely click on a link on a home page, and you'll automatically be sent there. It is easy to create documents that allow employees to find specific company information and related material quickly.

The Web uses client/server architecture to work. To access the Web, a client uses a Web browser program. Clients are available for all common types of computers, including PCs, Macintoshes, and UNIX workstations. Popular browsers include Netscape and Microsoft's Internet Explorer. The client/server model works well for an intranet, since it allows many different kinds of clients on different computers to be run, and yet the same corporate resources can be made available to all clients from the same servers. The operating system of a server need not be the same as the operating system of a browser. Popular operating systems for servers include UNIX and Windows NT.

Corporations often standardize on a particular browser such as Netscape or Internet Explorer, so that everyone on an intranet will use the same kind of browser. This is done because the language of the Web-the Hypertext Markup Language-has not been truly standardized. Additionally, each browser has slightly different capabilities, so pages designed for one browser may not display very well in another browser.

Home pages on an intranet (and the Internet) are built using a page markup language called HTML (Hypertext Markup Language). This specialized language contains commands that tell browsers how to display text, graphics, and multimedia files. It also contains commands for linking the home page to other home pages, and to other Internet resources. HTML is a constantly evolving language, and with each new generation it gets additional capabilities. While there are HTML standards, there are also variations on the language, so those who build intranets have to be careful to use HTML commands that their company's standard intranet browser will easily understand.

It's the browser's job to contact Web servers, receive HTML pages, and then interpret and display those pages. Web locations on an intranet are specified by URLs-uniform resource locators. You type in the URL in your browser, or click on a link in order to navigate to a particular Web page. The packets making up the request are sent to an intranet router, which checks the destination address, and then routes the request to the proper server.

When you type in the URL, the Web browser looks at the URL and then determines which server to contact, which directory to ask for, and what specific document in that directory is the one that you want. It then uses HTTP (Hypertext Transfer Protocol) to contact the Web server and request the document that you're interested in. HTTP is an application level protocol.

The Web server receives requests from browsers using HTTP. Its job is simple: to deliver the page or other object to the browser, using HTTP. It receives the request and sends the requested information back to the Web browser. After it sends the information, the connection is closed. In this way, the intranet's resources can be used most efficiently, since whenever the server isn't sending or receiving data, it's available.

Increasingly, the Web is becoming a true multimedia environment. It allows for animation, video, and other forms of interactivity. It does this in a variety of ways. One way is by using a programming language called Java, which allows intranet programmers to create interactive applications delivered over the Web. Java applets require that Web browsers be able to read the language. Popular browsers like Netscape Navigator are able to do that.

Another way that the Web is becoming a multimedia environment is by the use of an increased amount of sound files. Web browsers by themselves often won't be able to play these kinds of files. Sometimes, home pages contain links to files that the Web browser can't play or display, such as sound and animation files. In that case, you'll need a helper application. You configure your Web browser to use the helper application whenever it comes across a sound or animation file that the browser itself can't run or play. A special kind of helper application is known as a plug-in. Plug-ins allow the sound, animation, or video to play right inside the Web browser. You don't need the browser to run a separate program, as you need to with helper applications.

The Web is important for intranets because, increasingly, it is a way to allow people within corporations to be able to mine the rich amounts of data found in corporate databases. Before intranets and the Web, it was often difficult to give many people access to this information. The relative ease of publishing and creating forms with HTML makes it easier to give people access to this information. Often, some kind of link needs to be forged between the Web and a corporate database that allows someone on the intranet Web to query a database that doesn't understand HTML. One way to do this is to use the Common Gateway Interface (CGI). With CGI programs or scripts, an intranet programmer can allow someone from the Web to search a database, and then have the information sent back to that person in an HTML page that's easy to read and understand. The data can be sent back with new HTML links that would lead the user to other data, allowing for expanded interactivity with the information.

In some ways, intranet Web servers work the same as their Internet counterparts. Both receive requests specified by the HTTP request from Web browsers, and both send back the resulting pages using the TCP/IP protocol as the actual delivery mechanism. But there are some major differences as well. Inside an intranet, Web pages can be delivered at higher speeds than pages delivered over the Internet. That's because corporations can build high-speed intranets that aren't bedeviled by the traffic problems, bad connections, and low-bandwidth connections common on the Internet. So when someone inside an intranet requests a Web page, that page can be delivered from the server to the browser at a much higher speed-which is significant, considering that many pages are rich with graphics, sounds, and other multimedia files, which can take a long time to deliver over the Internet.

Intranet Web servers can also find ways to deliver information from the Internet to intranet users at high speeds. An intranet Web server can cache pages in memory that intranet users commonly request. It is important to realize, however, that pages from the cache are not updated, so technically, the data contained in them may have changed-with serious consequences if the item being retrieved is a stock quote or an inventory figure.

A company with an intranet may want to publish some of its information on the intranet, or allow people on the intranet to buy goods and services through it. In this case, the company will not only have their normal private intranet servers-they'll also have public Internet servers as well. Public information that anyone can see will be on the Internet servers. However, the company will still have intranet servers behind a corporate firewall, protecting vital corporate data from Internet access.

How Intranet Webs Work

The heart of any intranet is the World Wide Web. In many instances a large part of the reason that an intranet was created in the first place is that the Web makes it easy to publish company-wide information and forms by using the Hyptertext Markup Language (HTML). The Web allows for the creation of multimedia home pages, which are composed of text, graphics, and multimedia contents such as sound and video. Hypertext links let you jump from any place on the Web to any other place on the Web, which means that you can jump either to places inside an intranet or outside on the greater Internet from a home page.

  1. Intranet Webs are based on client/server architecture. Client software-a Web browser-runs on a local computer, and server software runs on a Web intranet host. Client software is available for PCs, Macintoshes, and UNIX workstations. Server software runs on UNIX, Windows NT, and a variety of other operating systems. The client software and server software need not run on the same operating system. To use an intranet Web, first launch your Web browser. If you're directly connected to your intranet, the TCP/IP software you need to run the browser will already be installed on your computer.
  2. When browsers are launched, they will visit a certain location by default. On an intranet, that location may be a departmental Web page or a company-wide Web page. To visit a different location, type in the intranet location you want to visit, or click on a link to the location. The name for any Web location is the URL (uniform resource locator). Your Web browser sends the URL request using HTTP (Hypertext Transfer Protocol), which defines the way in which the Web browser and the Web server communicate with one another.
  3. If the request is for a page found on the intranet, routers send the request to that intranet Web page. A very high-speed connection may be available, since intranets can be built using high-speed wires, and all traffic inside the intranet can be conducted over those wires. Internet connection can be much slower because of the amount of traffic on the Internet, and because there may be a variety of low-speed connections that the request from the intranet will have to traverse. The packets that make up the request are individually routed at the network level of the OSI model to an intranet router, which in turn sends the request to the Web server.
  4. The Web server receives the request using HTTP. The request is for a specific document. It sends the home page, document, or object back to the Web browser client. The information now is displayed on the computer screen in the Web browser. After the object is sent to the Web browser, the HTTP connection is closed to make more efficient use of network resources.
  5. URLs contain several parts. The first part-the "http://"- details what Internet protocol to use. The "" segment varies in length and identifies the Web server to be contacted. The final part identifies a specific directory on the server, and a home page, document, or other Internet or intranet object.