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Chapter 1: An Introduction to Networks
COMPUTER NETWORKS ARE everywhere. You find them in large businesses and small ones, schools and charitable institutions, government offices, and high-school students' bedrooms. In today's world it's important to know what networks are and how they can help you.
If you are responsible for a network, you need to understand how the network works and how you can most effectively tailor the network to the needs of your organization. Networks are sophisticated and complex tools, but they need not be difficult to understand and use. With a little study and some hands-on experience, you can make networks work for you.
What Is Networking?
IN THIS SECTION you will learn what networks are and how networks can enhance the usefulness of your computers. This discussion introduces you to the computer as an information tool and then shows you how networks enhance the computer's ability to exchange, share, preserve, and protect information. You will also see how networks can make it easier to share expensive hardware and software.
Networking Is All about Information
Every business runs on information, whether the business is banking, drycleaning, aerospace, or computer chip manufacturing. Inventory and payroll, account balances, contact lists, and customer preferences are all types of information that are vital to a successful business.
The type of information changes from business to business and industry to industry, and the way that information is stored and worked with also varies:
- A sole proprietor of a small business may keep business information in
- A bookstore may track the ebb and flow of sales on paper.
- A multinational corporation may have mainframe computers and an army of technicians to care for the corporate knowledge base.
- An engineering firm may store technical specifications on a network server and coordinate changes by e-mail.
More and more businesses, small and large, now rely on personal computers and networks to store their precious information.
Tip:Consider how you use information in your work. Look around and see the information flowing about you. Imagine how a network might make it flow more quickly or efficiently.
- What information does this agency maintain?
- A bakery produces and delivers doughnuts and cakes to coffee shops around town.
A software company develops sophisticated graphics packages for Windows and Macintosh computers. The company sells the software through regular software distribution channels and directly to the consumer through mail order. The company provides a generous upgrade path to registered users of the company's software. * What information does this company maintain?
- What information does this company maintain?
Tip: Microsoft provides exam objectives to give you a very general overview of possible areas of coverage of the Microsoft exams. The actual Microsoft exams, however, tend to emphasize certain of these exam objectives, while ignoring others. For this reason, you will find that some exam objectives are covered here in great detail, while others are only touched upon lightly. You will also find that we cover several areas that are not directly related to the exam objectives, but are fundamental to understanding the essentials of networking.
The Personal Computer as an Information Tool
The personal computer is a fantastic information tool. It gives you the ability to control the flow of information in your life. But it is shipped from the manufacturer with just enough software to make it run and be marginally useful; it is up to you to customize it for your own purpose. With the right software, your computer can meet nearly any information-processing need; for example, a dog-grooming shop can track animals and their owners with a specialized database, and a legal firm can search CD-ROM legal archives and prepare briefs with word processors. A graphics design house can manipulate images with graphics software, and an engineering firm can track numbers with spreadsheets. Figure 1.1 illustrates some of the benefits a computer can bring.
An entire industry-software publishing-exists to customize the personal computer for any use imaginable. Specialized software exists for almost any market niche, whether it is meat-packing or bookstore inventory management. There is even software available specifically to help carpenters design cabinets for houses.
Information constantly flows through your business. Orders are taken in the sales department and passed through to shipping; research and development sends new device specifications to manufacturing; accounting collects statistics and passes them to management. A small design house distributes parts of a project to the various members of a team, who work together to prepare a final, integrated proposal. A publishing house collects market projections, receives manuscript drafts, delivers edited proofs, and requests corrections and elaboration, and finally a book is sent to be printed.
Once, all business information was transmitted verbally or on paper. Before networks, even with the computer, people had to personally move the information about, whether it was on paper, over the phone, or on floppy disk or magnetic tape.
When you use a computer not connected to a network, you are working in what is called a stand-alone environment. You can use software to produce data, graphics, spreadsheets, documents, and so on, but to share your information you must print it out or put it on floppy disk so that someone else can use it. You are moving the information about yourself rather than letting the computer do it for you. Figure 1.2 illustrates a stand-alone environment.
Computers connected over a network can make that information exchange easier and faster. The information moves directly from computer to computer rather than through a human intermediary. People can concentrate on getting their work done rather than on moving information around the company.
The most elementary network consists of two computers communicating over a cable. When you link computers together, you can more swiftly and efficiently move information between them. The computers can also share resources, such as printers and fax modems, allowing you to better use your hardware. A group of computers and other devices connected together is called a network, and the concept of connected computers sharing resources is called networking.
other by cable in a single location, usually a single floor of a building or all the computers in a small company. The most common cabling method in the 1980s allowed about 30 users on a maximum cable length of about 600 feet. Figure 1.3 shows a simple local area network.
Often, businesses have offices throughout a large region. For instance, most banks have a headquarters site and offices throughout a city, state, or nation. While local area networks are perfect for sharing resources within a building or campus, they cannot be used to connect distant sites.
Wide area networks (WANs) fill this need. Stated simply, wide area networks are the set of connecting links between local area networks. These links are made over telephone lines leased from the various telephone companies. In rare instances, WANs can be created with satellite links, packet radio, or microwave transceivers. These options are generally far more expensive than leased telephone lines, but they can operate in areas where leased lines are not available. Figure 1.4 shows a simple wide area network.
Most WANs are private and owned by the business that operates with them. Recently, however, the Internet has emerged as both the largest and the least expensive WAN in the world. Many companies are now forming private WANs through encrypted communications over the Internet.
WANs suffer from extremely limited bandwidth. The fastest commercially feasible wide area data links are many times slower than the slowest local area links. This makes the sharing of resources over a WAN difficult. Generally, WAN links are used only for interprocess communications to route short messages, such as e-mail or HTML (World Wide Web) traffic....