If you are used to working on a single computer, the idea of setting up a network might seem daunting. Perhaps at work you do plug in to the corporate network; however, maintaining and configuring this network isn't your problem but is instead handled by a staff of highly professional overachievers. At least, that's what the folks from corporate information technology (IT) would have you believe.
Relax! There's nothing particularly dark, deep, or mysterious about the concepts involved in setting up a small home or office network.
I'd like to step back for a moment or two and forget about Wi-Fi and wireless connectivity. This will give me the chance to explain networks to you generally. As you'll see, networks are really simple. There are no really tough concepts involved. By explaining the concepts and showing you the relevant vocabulary, I can help make sure that you'll make the right purchasing decisions (and never be snowed by a salesperson's jargon).
The only real difference between wired and wireless networks is the following:
In the Beginning, There Was the Connection
At its most basic level, a network is simply two or more computers or devices that are connected, as shown in Figure 11.1.
Figure 11.1. The simplest network consists of two connected computers.
Most modern networks, including the Internet itself, use a protocol called TCP/IP (Transmission Control Protocol/Internet Protocol) to standardize communications.
Many devices can be added to a network. A good example is a network-enabled printer. However, in this chapter, I'm pretty much just going to talk about computers and devices generically, and I'll essentially be using the terms "computer" and "device" synonymously.
You don't really need to know anything about TCP/IP to use wireless networking (or wired networking, for that matter). But you might be interested to know that TCP/IP consists of a number of different so-called layers that specify how network transmissions are broken down into units, called packets, and reassembled, and much more.
TCP/IP is distinct from the mechanism used to convey the communication, meaning that if your network is operating over a wired connection, such as 10BASE-T Ethernet, the TCP/IP transmissions pass "over" the 10BASE-T wires. Similarly, if your network operates using Wi-Fi, TCP/IP transmissions are occurring "on top of" the Wi-Fi signals.
To Serve or Not to Serve
From a practical viewpoint, there are really two different ways that a network can be arranged. The arrangement of a network is called a network topology.
The simplest setup is one in which computers share resources such as files, printers, and Internet access on an ad-hoc basis. This is often called a peer-to-peer network. At a concept level, which means forgetting about things such as whether the connections are made with wires or radio waves, a peer-to-peer network might resemble the one shown in Figure 11.2.
Figure 11.2. In a peer-to-peer network, computers share their resources.
The other type of network topology, client/server, is somewhat more complex. In this kind of setup, a centralized server computer controls and polices many of the basic functions of the network. For example, the server is used to authenticate users and to make sure that they have permission to take specific actions in respect to resources. In this kind of setup, only specific users (or kinds of users) may be allowed to modify or delete files. (Although individual computers can share resources directly, the sharing can only take place if the policies established on the server allow it.)
It's hard to enforce this kind of policy on a network without a centralized server. At a conceptual level, forgetting for the moment how the computers are actually connected, a client/server network might resemble the one shown in Figure 11.3.
Figure 11.3. In a client/server network, a central server controls the resources shared by client computers.
Generally, client/server networks are found in larger-scale enterprise environments. I've described them here in case you work in an environment that has this kind of network. But you probably don't need anything as complex (and expensive) to administer in your home or small office. For the sake of keeping things simple, in this chapter I'll assume that you are interested in assembling a peer-to-peer network (or already have such a network that you'd like to add Wi-Fi capabilities to).
A hub is a wired device that is the simplest way to connect three or more devices. A hub is basically a box that networked computers connect to via several ports. The hub simply replicates the signals coming into each of its ports and sends the signals to each of its other ports. This is another way of saying that the hub receives information from any device plugged in to it and transmits the information to all other connected devices. It neither knows nor cares which devices the information is going to. It is up to each individual device to pick up the data meant for it. Plugging four devices in to a hub has more or less the same result as connecting the devices to each other.
Typical wired hubs are very inexpensive and come with four or five sockets for connections to computers, but some hubs can have a great many more connections.
You might have heard the term switch in connection with networks. A switch is just an intelligent hub. Like a hub, a switch is a device used to connect computers. But a hub has no smarts and simply replicates the signals coming in from each computer and passes the signal along to all the connected computers. In contrast, a switch has built-in "intelligence" that understands where to send transmissions.
Small networks usually don't need switches. The busier the network becomes, the more important it is to use intelligent switches rather than hubs.
These days, even lower-end hubs tend to have some intelligence built-in and are called switches.
Figure 11.4 shows an inexpensive switch in use as a simple hub.
Figure 11.4. An inexpensive hub/switch in use.
A router sits between one network and another. If you are interested in setting up a small home or office network, you are likely to use a router to connect the Internet (the largest network of all) with your small network.
Let's suppose that you have a cable modem, or a DSL modem, connected to the Internet at your home. The router connects to the modem and also to your home network, as you can see in Figure 11.5.
Figure 11.5. The router sits in between the Internet connection and your home network.
You should know that most routers also function as hubs/switches and provide four or five wired connection sockets. As I'll discuss shortly, routers also come with Wi-Fi. So it's very common these days to buy one inexpensive, little box that combines the features of a wired router with those of a Wi-Fi access point.
If you only plan to connect a few devices to your network, in addition to your modem, you probably only need a router. You can always add hubs as you need them.
Figure 11.6 shows a wired router in use.
Figure 11.6. This wired router distributes an Internet connection across a small network.
As I mentioned, it's common to combine wireless capabilities with those of a router. Figure 11.7 shows a device that combines a wired router with Wi-Fi (as you can tell by the antenna on the upper right, and the networking cables that are plugged in to the device).
Figure 11.7. This device combines a wired router with Wi-Fi wireless broadcast capabilities.
Besides their function as a kind of gateway between networks, most routers provide some additional functionality. Routers can make Internet access possible by translating local network addresses to ones that work on the Internet, a feature called Network Address Translation (NAT), and by assigning network addresses to local machines on-the-fly. This enables the computer (or computers) that make up your home network to interact with servers on the Internet.
Most routers also include features that protect your data by blocking some kinds of information from accessing your network using what is known as a firewall. A firewall is a blocking mechanismeither hardware, software, or boththat blocks intruders from accessing a network or individual computer. For more about using personal and network firewalls, see Part V, "Securing Your Computer and Network."
What Is the Network?
How many stars are there in the sky at night, and how vast is the network? Before I wax too poetic, let me get to the point!
Small networks are created by connecting devices, usually via a hub. Larger networks are simply aggregations of small networks, with the small networks connecting to each other, and to the Internet, via routers.
Although these building blocks are very simple, it is obviously possible to create complex network topologies, or arrangements of a network, using them. There are in fact infinite varieties of the possible ways to arrange networks.
You'll have to fit the network topology you create to your physical needs. How many computers do you need, and where?
As an example, Figure 11.8 shows a fairly simple network topology that has seven connected devices and uses a router and two hubs.
Figure 11.8. You need to create a network topology based on your physical requirements.
It's worth stepping back for a second and thinking about what you are creating when you string together computers to make a network. By combining computers in a net work, you've created a new entity (the network) that has more computing power than any individual device on the network. Hallelujah! It gets even better when you use a router to connect your network to even more powerful external networks such as the Internet. Effectively, you've harnessed the power of many discrete networks running all over the world in every node of your home or small office.
When this kind of network has become commonplace (or "ubiquitous" as they say in marketing departments), what really is the computer? It doesn't seem right to think of the computer as limited to a single CPU (or box and monitor) when the computer is functioning as part of a network. Maybe the network really is the computer. How much more powerful, and easy, it all becomes when you don't need wires to make the network connections, and you can take your computer (for example, the network) everywhere you go.