Tom's Hardware and Que Publishing are partnering up to give you four chapters from Scott Mueller's Upgrading And Repairing PCs, 20th Edition. We're also giving away copies of the book to 10 lucky Tom's Hardware readers. To enter, please fill out the contest form, and remember that you can only enter once (if you entered when we published Computer History 101 or Hard Drives 101: Magnetic Storage, we already have your entry).

This third chapter we're making available from Scott's book covers the basics of a Local Area Network (or LAN). Don't forget to check out the previous chapters published on Tom's Hardware, Computer History 101: The Development Of The PC and Hard Drives 101: Magnetic Storage. In the days to come, we'll also present comprehensive looks at LAN Hardware and Assembly, and Power Supplies.

A network is a group of two or more computers that intelligently share hardware or software devices with each other. A network can be as small and simple as two computers that share a printer or as complex as the world’s largest network: the Internet.

Intelligently sharing means that each computer that shares resources with another computer or computers maintains control of that resource. Thus, a USB switchbox for sharing a single printer between two or more computers doesn’t qualify as a network device; because the switchbox—not the computers—handles the print jobs, neither computer knows when the other one needs to print, and print jobs can potentially interfere with each other.

A shared printer, on the other hand, can be controlled remotely and can store print jobs from different computers on the print server’s hard disk. Users can change the sequence of print jobs, hold them, or cancel them. And, sharing of the device can be controlled through passwords, further differentiating it from a switchbox.

You can share or access many different types of devices over a network, but the most common devices include the following:

• Printers
• Storage drives
• Modems
• Cameras
• Media players/recorders
• Game consoles

Entire drives or just selected folders can be shared with other users via the network.

In addition to reducing hardware costs by sharing expensive printers and other peripherals among multiple users, networks provide additional benefits to users:

• A single Internet connection can be shared among multiple computers.
• Electronic mail (email) can be sent and received.
• Multiple users can share access to software and data files.
• Files and folders can be backed up to local or remote shares.
• Audio and video content can be streamed to multiple devices.
• Multiple users can contribute to a single document using collaboration features.
• Remote-control/access programs can be used to troubleshoot problems or show new users how to perform a task.

Types of Networks

Several types of networks exist, from small two-station arrangements, to networks that interconnect offices in many cities:

• Local area networks—The smallest office network is referred to as a local area network (LAN). A LAN is formed from computers and components in a single office or building. LANs built from the same components as are used in office networks are also common at home.
• Wide area networks—LANs in different locations can be connected by high-speed fiber-optic, satellite, or leased phone lines to form a wide area network (WAN).
• The Internet—The World Wide Web is the most visible part of the world’s largest network, the Internet. The Internet is really a network of networks, all of which are connected to each other through Transmission Control Protocol/Internet Protocol (TCP/IP). It’s a glorified WAN in many respects. Programs such as web browsers, File Transfer Protocol (FTP) clients, and email clients are some of the most common ways users work with the Internet.
• Intranets—Intranets use the same web browsers and other software and the same TCP/IP protocol as the public Internet, but intranets exist as a portion of a company’s private network. Typically, intranets comprise one or more LANs that are connected to other company networks, but, unlike the Internet, the content is restricted to authorized company users only. Essentially, an intranet is a private Internet.
• Extranets—Intranets that share a portion of their content with customers, suppliers, or other businesses, but not with the general public, are called extranets. As with intranets, the same web browsers and other software are used to access the content.

Note: Both intranets and extranets rely on firewalls and other security tools and procedures to keep their private contents private.

Requirements for a Network

Unless the computers that are connected know they are connected and agree on a common means of communication and what resources are to be shared, they can’t work together. Networking software is just as important as networking hardware because it establishes the logical connections that make the physical connections work.

At a minimum, each network requires the following:

• Physical (cable) or wireless (usually via radio frequency [RF]) connections between computers.
• A common set of communications rules, known as a network protocol.
• Software that enables resources to be served to or shared with other network-enabled devices and that controls access to the shared resources. This can be in the form of a network operating system or NOS (such as older versions of Novell Netware) that runs on top of an operating system; however, current operating systems (OSes), such as Windows, Mac OS X, and Linux also provide network sharing services, thus eliminating the need for a specialized NOS. A machine sharing resources is usually called a server.
• Resources that can be shared, such as printers, drives, modems, media players, and so on.
• Software that enables computers to access other computers sharing resources (servers). Systems accessing shared resources are usually called network clients. Client software can be in the form of a program or service that runs on top of an OS. Current OSes, such as Windows, Mac OS X, and Linux include client software.

These rules apply both to the simplest and the most powerful networks, and all the ones in between, regardless of their nature. The details of the hardware and software you need are discussed more fully later in this chapter.