No, Really, What Is a Network?

I'll start with a nice, purposefully broad definition of network and then show some examples:

Network A combination of hardware, software, and cabling, which together allow multiple computing devices to communicate with each other.

In short, a network gives computers the ability to communicate. However, that definition could apply to a lot of different types of networks. So, some examples can help. Figure 1-1 shows the basic idea of a typical small network used by a company at a single site.

Figure 1-1. Simple Single Site Network

Remembering the definition, a network consists of hardware, cabling, and software. Figure 1-1 does not show some of the hardware, and it shows no cabling; the cloud represents those parts of the network. A cloud in a network diagram simply means that there are network componentshardware, software, and cablingbut the details are hidden because they are not important to the current discussion.

Figure 1-1 does show some important parts of the networkin particular, the server and the client end user computers, typically personal computers (PCs). In networks, a server provides some form of service to the users in the network. In this case, both users store files on the server, and they print files on the printer that is attached to the network. Many of you probably do that every day you are at work or at school.

This simple network does fit the definition of a network. Even though you cannot see some of the details, this network allows the computers to communicate. But like the three blind men and the elephant, depending on your job, you might have a totally different view from what this network looks like in real life.

What an Elephanterr, a NetworkLooks Like

Now would be a good time to take a closer look at what's behind the cloud, shown in Figure 1-2.

Figure 1-2. A Closer Look at the Simple Network

As shown in Figure 1-2, User1's PC has networking software installed. A cable connects that PC to a socket on the wall. That socket has a cable on the (hidden) other side of the wall plate. The cable runs under the floor, in the ceiling, or some other hidden place, with the other end being in a wiring closet. The wiring closet is typically a small room (hence the word closet) where all cables from all the computers run.

Inside the wiring closet, all the cables connect to a switch. A switch consists of specialized hardware and software that forwards the network traffic back and forth between the various network devices on the network.

Three Blind MenThe Server Guy, the Cabling Guy, and the Network Guy

Depending on where you work, you might have a lot of different people working on the network. In some companies, one person is responsible for all parts of the network. In other companies, the responsibilities are divided among lots of different people. In some cases, you simply need different skills to perform different tasks. In other cases, one job might reside in a different department for organizational reasons. Union personnel often run the cables.

Because different people often work on a different aspect of a network, they form their own prejudices about what a network really isand is not. So, like the three blind men and the elephant, each type of worker might develop a tendency to ignore or discount parts of the network. Although most people are not so narrow-minded as the people I'm about to describe, people tend to build their own views based on their own experiencesand that's true when working with networks as well.

For example, imagine the person who is responsible for the server. That person needs some PC hardware skills, but more importantly, he needs strong skills with software. The hard partand fun partof supporting the server has to do with software installation, testing, administration, and troubleshooting.

However, the server guy might not know what's on the other end of the networking cable. In fact, he might perceive the world like Figure 1-3.

Figure 1-3. The Server Guy's Perception of the Network "Elephant"

Okay, the size of the server in Figure 1-3 is meant to be a little ridiculous, but that, of course, is the focus of the server guy. He also worries about the client PCs. He views the rest of the network as a network utility. The term network utility simply refers to the idea of treating the rest of the network just like you think of the telephone, electrical power, water, and so on. You expect it to work, and it usually does; you generally do not think about it unless it's not working.

The cabling guy and the network guy actually create the network utility. The cabling guy, typically called an electrician, might also have a narrow view of the world. His job requires that he run the cables from each cubicle back to the wiring closet. His job requires physical dexterity, knowledge of how to conform to the electrical building standards, and a willingness to get a little dirty when running cables under the floor, in the ceiling, or through some other hole in the wall. To him, the network is the cabling.

The cabling guy makes sure that there's a working cable running from the wiring closet to each place in the building where a computer needs to connect to the network. Figure 1-4 shows the basic perspective of the cabling guy.

Figure 1-4. The Cabling Guy's Perception of the Network "Elephant"

The electrician (cabling guy) typically takes care of running cable from each wall plate to the wiring closet, with the cable being run under the floor or inside the ceiling. The wall plate simply provides a physical plug into which the electrician can connect a short networking cable from any computer. The wiring panel gives the electrician a place to physically connect the end of the cables so that the network engineer (or the cabling guy) can easily connect the ends of the cables to the switch. The cabling guy's focus is on installing, testing, and troubleshooting the cabling from each wall plate to the wiring closet.

Finally, the network guymore often called the network engineeris responsible for the switch, as well as any other hardware and software used to create a network utility for the computers. The network engineer installs, supports, and troubleshoots the hardware and software on the switch. To do his job, he needs to know where each cable runs and to what port in the switch each cable is connected. However, the network engineer does not always need to know exactly where the cabling travels to get to the wall plate. His view of the world is depicted in Figure 1-5.

Figure 1-5. The Network Guy's Perception of the Network "Elephant"

From the networking guy's perspective, there's simply a cable run from the switch to each device; in other words, he ignores all the difficulty the electrician went through to get all the cables run. However, he does know which computer's cable plugs into the various numbered ports on the switch. (A switch typically has lots of places into which you can plug in one of these networking cables; these places where you plug in the cable are called switch ports.)

The network guy does want to know where the server sits so that he can confirm that the server can indeed send and receive traffic across the network. The network guy might even care to know what type of services the server is providing. But the network guy typically needs to know a lot less about the servers than the server guy does.

note

The network shown in these past few figures is typically called a local-area network (LAN). A LAN is a network for computers that are nearby or local to each other. The second part of this book covers in much more detail how LANs work.

The interesting thing about all three types of networking workersand others as wellis that they are all correct to some degree. Without the cabling, the network won't work. Without some networking devices, most networks will not work. If you do both of those things correctly, you have created a network utility, but without working servers, the end users will not have anything useful to do with the network. So, although all three types of workers might have different views of the network, they all need to do their jobs well for the network to be useful.