Using a World-Wide Network (the Internet)
- Using a World-Wide Network (the Internet)
- Smaller than the Internet, Bigger than a LAN (Intranets and Extranets)
- Where To From Here?
- The Least You Need to Know
Using a World-Wide Network (the Internet)
In This Chapter:
Understand how the Internet, intranets, and extranets are used
Learn how domain name system naming and IP addressing identify computers to the network
Find out what resources are available on the Internet
Understand how intranets can be used in a corporate environment
Learn how extranets can extend the boundaries of a corporate intranet
So, a little, private LAN isn't big enough for you? You want to be able to connect with people and computers all over the world? Well, if you haven't heard of the Internet before, then let me be the first to welcome you back from your decade-long shipwreck on a desert island. The Internet is here to stay and waiting for you to hop on.
Most people who have used the Internet have done it by dialing into an Internet service provider (ISP) from a PC at home or from some invisible hookup configured by a system administrator at work. Most people don't know where the Internet came from or how it works.
The Internet is a massive computer network consisting of thousands of subnetworks and millions of computers worldwide. Although it began as a U.S. military project in the 1960s (used primarily by government agencies, universities, and government contractors), today it encompasses a vast range of commercial, educational, and recreational uses.
The World Wide Web
Although the number of computers and users on the Internet has grown since its inception, its greatest growth period began in the late 1980s with the creation of the World Wide Web. The Web placed a simplified framework over the Internet that enabled non-technical people to use the Internet for the first time.
Tim Berners-Lee invented the Web in 1989 as a project for organizing documents at the European Laboratory for Particle Physics (CERN). As Berners-Lee published information on the Web, organizations began adding Web servers. However, it is generally agreed that the release of Mosaic (a free, graphical Web browser from Marc Andreessen at the National Center for Supercomputing Applications) in 1993 spurred growth by making Web browsing available to a much wider audience. In 1993, NCSA and CERN formed the World Wide Web Consortium (http://www.w3c.org/), which is still responsible for setting the course for the future development of the Web.
The Web made the Internet more accessible to the masses in the following ways:
Created Hypertext Markup Language (HTML) This enabled users to build graphical documents that contained images, formatted text, and links to other documents on the Web. Now HTML documents can include sound, video, and other content as well.
Created a simplified way of identifying Web resources Using uniform resource locators (URLs), a user can ask for a resource (such as a Web page or an FTP directory) directly from a server. Before, users had to log in to a computer, search for what they wanted, download a file, and then open it using an appropriate program.
The Web relies on the Internet's computer naming system, called the domain name system (DNS), as the basis for URLs. DNS is described later in this chapter. To specifically identify Web resources (documents, images, and so on), URLs add other information to host names. Figure 3.1 shows an example of a URL.
The first part of a URL identifies the protocol needed to display Web content. For Web pages, Hypertext Transfer Protocol (http://) appears in front of the address. For File Transfer Protocol, the prefix ftp:// is used. The location of the resource on the server is placed at the end of the computer name. For example, a file, or resource, called swanhous.jpg in the /images directory on the Web server is added on as /images/swanhous.jpg.
The port number is one piece of information that is implied, although usually not included, when you enter a URL. When your Web browser requests a service from the Web server, a particular port is requested to fulfill that service. For example, HTTP is port 80 and FTP is port 21 by default. To ask for the port specifically, you add a colon (:) followed by the port number to the end of the URL. For example:
In this case, the :80 is not needed because port 80 is assumed. However, if Web service (or other service that you want) were available on a different port number, you would have to type that number instead of 80.
The Web browser is the program you use to access resources on the Web. Although browsers were first intended primarily to display Web pages (in HTML format), browsers have turned toward a one-program-fits-all approach.
How the Internet Works
Many of the design considerations that went into the early versions of ARPAnet, the predecessor to the Internet, are still apparent in the Internet of today. Because it began as a military project intending to ensure that computing resources had the capability to continue to respond during a nuclear attack (so the government could shoot back), the network had to have the following attributes:
Keep running no matter what There could be no single point of failure that caused the network to stop running. Even if whole areas of the network were destroyed, the remaining parts had to continue to communicate.
Join together incompatible equipment Communication needed to occur between computing systems of different agencies that were often incompatible. Usually they weren't even capable of sharing files, let alone communicating over networks in any meaningful way.
To meet the first criterion, the government decided to make the network a packet-switching network. Rather than have two communicating computers set up a connection and send data across that connection (like a telephone call), data is broken up into packets, with each packet labeled with the source and destination address of the data (like sending a letter at the post office).
The advantage of packet switching is as follows: Because each item of data knows where it is going, information can take any available route to reach the destination, and then be reassembled when the packets get there. If part of the network goes down, packets can take another route because communication doesn't rely on a particular connection staying up during the course of a communication.
As for the criterion of connecting incompatible computing systems, instead of replacing existing networks and computers, the Internet acted as an umbrella by placing new protocols over existing ones. As a result, the many types of networks available today can all be part of, and carry data for, the Internet by adding TCP/IP support to those networks.
The impact of this design on today's Internet is that the Internet can continue to grow by adding faster, higher-bandwidth backbones. A high-bandwidth backbone is like a superhighwayit allows a lot of data to be transported quickly over long distances. Older, less efficient networks can be retired. Internet traffic can be routed to networks that are less congested. Furthermore, even though it might be slower, the Internet itself can continue to work when parts of the network go down.
Resources on the Internet
The transformation of the Internet that was brought about by the Web marked a major change not only in who was using the Internet, but also in the way the Internet was used. Originally, users tended to be technical workers or students, as opposed to today's potential useranyone with access to a PC and a modem. Furthermore, Internet programs were command-oriented instead of graphical.
With the transition to the Web, traditional technical and educational uses have given way to entertainment, shopping, and a wide range of business applications. The following sections describe both the traditional and current uses of the Internet.
Traditional Internet Uses
If you were using the Internet BWBefore Webhere are some of the things you were probably doing:
Email Mail messages were plain text (that is, letters you can type from the keyboard), with an occasional attachment containing a binary file (that is, special data files or programs). You probably needed to know how to use a command such as uudecode to decode any attached images or data.
Newsgroups This was, and remains today, a popular resource for exchanging ideas and information on topics of interest. Although improvements have been made, such as threads (to group responses by a particular newsgroup question) and HTML messages (which people with old newsreaders find annoying because HTML appears as junk in those readers), newsgroups continue to operate today much as they did before the Web was created.
FTP (file transfer protocol) To download software and documents from other computers, you can use the ftp command to access computers that are set up as FTP servers. After you log in, usually using an anonymous login, you can go up and down the directory structures to find and download the files you want. (With an anonymous login, you type anonymous at the FTP login prompt, and then your email address as the password. In this way, the FTP server can track you activities without requiring you to have a special user account on the computer.)
Gopher, WAIS (Wide Area Information Server), Archie Even before the Web, people realized that it was difficult to find documents by accessing one computer at a time and looking at filenames using the ftp command. To solve that problem, facilities for storing and indexing documents were created with programs such as Gopher, WAIS, Archie, and others.
Users did keyword searches to find documents of interest, and then selected a document from the resulting list to go to the site and get the document. Since the inception of the Web, however, with its tools that organize and search for documents much more effectively than facilities such as Gopher, WAIS, and Archie, the older programs are becoming obsolete.
FTP servers are still supported today, although Web pages are often used to navigate documents and download sites to simplify the task of finding the right resources.
Besides the services mentioned in the preceding list, there were also a variety of commands that were used with the Internet. For example, commands that can be run between two computers include telnet and rlogin (for remote login), rcp (for remote file copy), and rsh (to run commands remotely). These commands are used primarily between trusted computers on UNIX and Linux systems. A trusted computer is one that you believe to be secure (that is, you trust that users with malicious intent cannot gain access to it and cause a potential security risk to your computer).
Today's Internet Uses
In the United States, it's practically impossible to find a major corporation, educational institution, or government agency that doesn't have a presence on the Web. From these organizations' Web sites, there is a dizzying array of information, products, and services being offered.
As noted earlier in this chapter, the Web browser is the primary tool for using the Internet. Products such as Microsoft Internet Explorer and Netscape Communicator have become full Internet access suites. Besides browsing, these products also contain tools for using email, participating in newsgroups, conferencing, creating Web pages, publishing Web content, and playing a variety of multimedia content (such as video and audio).
For a description of features in Microsoft Internet Explorer, please see Chapter 10, "Taking Your Network for a Drive."
Although the space allotted here can't begin to cover all the resources available on the Internet, the paragraphs that follow describe several of the major uses of the Internet today. If you are about to make your first journey onto the Internet, know that you need a connection to the Internet, a PC, and a Web browser to start. Following are some of the things available to you on the Internet:
Shopping sites Many expect online shopping and other types of commerce to become one of the major uses of the Internet. Online shopping offers convenience (it's open 24 hours a day), easy price comparisons, detailed product descriptions, and links to reviews and other supporting information.
Also, most anything you can think of can be purchased onlineequipment, clothes, videos, food, automobiles, and so on. There are also auction sites such as eBay (http://www.ebay.com/) where individuals auction almost every kind of item you can think of.
Methods for carrying out secure transactions have become quite good. Enter a credit card number, mailing address, and a few other pieces of information, and your order can appear at your door within a few days. Some sites offer access to many different online retailers. Those sites include the Yahoo! Shopping site (http://shopping.yahoo.com/), Lycos Shop (http://shop.lycos.com/), and AltaVista Shopping.com (http://shopping.altavista.com/). Figure 3.2 is an example of the AltaVista Shopping.com site.
News and information All the major news services, newspapers, and other information media have Web sites where you can get the latest news, entertainment, and sports information. You can even tailor many of those sites to show you news on particular topics or regions of the country. Examples of these sites include cnn.com, abc.com, and usatoday.com.
Portals and Search engines Find information by searching the Web for sites containing certain keywords or sites that fall into specific categories. Portal and search engine sites include yahoo.com, lycos.com, excite.com, hotbot.com, altavista.com, and many others.
A portal is a Web site that can be used as a general jumping-off point to the Internet, usually allowing you to customize the type and amount of information that appears on the page. The intent is to encourage you to use the portal as your home page or at least as a page you visit often. A search engine is a program that lets you do keyword searches to find content on the Web.
Financial sites You can bank online, trade stocks, or apply for loans to name just a few of the financial services available on the Web. There are also tremendous (yet dangerous) resources for researching investment opportunities. Most online brokers (including etrade.com, schwab.com, and ml.com) offer some free financial research information, as well as premium fee-based services for their clients.
Education Most colleges, universities, and even K12 schools have sites available on the Web. These sites can be resources for information about those institutions as well as a source for research information. You can even apply to some online colleges and universities and get a degree over the Internet. You can find educational institutions using keyword searches via a search engine or by finding categories of schools from portals such as Yahoo.com.
Entertainment Everything you might ever hope to know about movies, music, television, books, and other entertainment media can be found on the Web. Try Warner Brothers Online (http://www.wb.com), DreamWorks SKG (http://www.dreamworks.com), and Paramount Pictures (http://www.paramount.com) for recent movie clips and information.
Gaming You can download games and play them against online competitors right from your PC. There are traditional board games (such as chess), card games (such as bridge), and monster-killing games (such as Quake II and Doom).
Sports Major sports organizations (NBA, NFL, and MLB) have Web sites with tons of articles, pictures, and statistics. There are also many sports news organizations and plain old sports fanatics with Web sites.
Travel There are hundreds of Web sites that can help you find the perfect vacation spot, scope out its accommodations and tourist spots, and sometimes even book the travel arrangements.
Chat rooms These sites enable you to type messages or talk online to strangers all over the world. Chats associated with certain topics of interest can actually be quite useful. Sometimes you can join chat rooms where you can ask questions of entertainers, athletes, or politicians. One warning: Chat rooms are also magnets to Internet weirdos, so be careful what you divulge about yourself, and to whom.
These are just some of the general resources available on the Internet. To look into more resources on your own, go to one of the search engines that enable you to step through categories of topics (such as the Yahoo.com site). Then just start clicking topics that look interesting to you.
Figure 3.3 shows the Yahoo! home page (http://www.yahoo.com).
You might notice that the topics discussed here regarding the Internet are mostly those relating to organizations that want to make their resources available to the general public. By contrast, intranets want to limit network access to people within an organization and extranets want to limit network access to those who work closely with an organization.