Different Types of Traditional Computer Networks

So far, you have seen only one simple network with just a few computers. Of course, networks come in many shapes and sizes. So, it is useful to think about a couple of other example networks before diving into the upcoming chapters.

Big Company, Multiple Sites: An Enterprise WAN

Imagine that you work at a company that has multiple physical sites with locations in separate states. As a user of the network, you might realize that the network connects all sites. For instance, you might be able to view information about your benefits program, fill out forms to change something about your retirement plan investments, and so on. You know that the Human Resources department is at headquarters, and you are at a small branch office. So, you can easily assume that your company needs a networkin this case, an enterprise wide-area network (WAN). Figure 1-6 depicts a typical example.

Figure 1-6. A Larger Network: An Enterprise WAN

In Figure 1-6, you can see three remote branch offices, each with a couple of PCs and a printer. The headquarters site has more users (hence, more PCs), as well as several servers. Each remote site has a LAN, much like the LAN shown earlier in this chapter. However, now the network includes a cloud labeled WAN. The WAN is simply a part of the network over which the computers at each site can send and receive data from computers connected to the LANs at other remote sites.

Most people call the network shown in Figure 1-6 an enterprise network because the network is owned by and created by one company, and a company can be considered to be an enterprise. You will also hear of this type of network called an enterprise WAN because enterprise networks typically use WANs as part of the overall network.

Just You and Me and the Whole WorldThe Internet

The Internetand yes, that's a capital "I" in "Internet"has significantly changed the way people live. It has flattened the earth and allowed the free exchange of ideas worldwideamong billions of people.

The Internet is yet another computer network, but it is unique. The uniqueness comes in that almost all enterprise networks connect to the Internet. Also, individual users can connect to the Internet. To make it all work, companies called Internet service providers (ISPs) provide service to companies and individuals to connect them to the Internet. The result? Almost all computers on the planet can communicate with each other. The cultural implications of the Internet far outweigh the coolness of the technology, and the technology is pretty cool! Figure 1-7 shows the basic idea of the Internet.

Figure 1-7. The Internet, with Enterprises and Individuals Connected to It

Once again, clouds show that parts of a network exist, but the details are hidden. The idea is simple: If we create a core network called the Internet, and all companies and individuals connect to it, then everyone can communicate with everyone else. The Internet is so pervasive today that you can almost take it for granted!