Big and Scary Networks: The Simplest Introduction You'll Ever Read
It's easy to be overwhelmed by technical jargon, and the subject of networks has certainly been one of the worst examples of this. It often seems as though the experts like to throw around a lot of complicated language for no better reason than to confuse the uninitiated. Maybe that makes the experts feel as though they know something that's their little secret, but it's not very helpful to people who simply want something that works. Phrases like "Wi-Fi infrastructure mode," "stateful packet inspection," and "upstream bandwidth" simply don't belong in our vocabulary!
The truth is that a home network doesn't really have to be difficult or complex. You don't have to join some geek squad or spend hours learning a new language to successfully create a functioning home network. In fact, you'll find that the project is fairly simple and pretty satisfying.
What Networks Really Are
So just what is a network, anyway? And how does a home network compare to an office network?
These are both good questions that get right to the heart of the matter. Let's start with the first question.
A network is nothing more than something that provides the means for different things to communicate with each other. You already use one of the world's biggest networks whenever you make a telephone call. Your phone number is the key that enables other people to pick up their phone, dial your number, and talk to you from virtually anywhere on the planet. Computer networks function very much like the telephone network because they were actually modeled after the telephone network to a large extent. Figure 1-1 gives you an idea of how home networks function, and Figure 1-2 shows how the telephone network is quite similar.
Figure 1-1. A Home Network Connects Your PCs and Other Devices So That They Can Communicate
Figure 1-2. The Telephone Network Functions Much Like Your Home Network Except on a Larger Scale
It's true that when you use a computer network, you typically aren't expecting another person to be at the other end of the line, but you don't always expect that with the telephone network, either. After all, haven't you ever made a phone call hoping that you would get someone's answering machine instead of talking directly to that person? When you do get the answering machine, you're interacting with that machine in much the same manner as if you were using a typical computer network and the devices on that network. Similar to how two network devices might communicate, the answering machine gives you a message, waits for your response, and then saves your response so that it can be picked up later.
So, if networks aren't all that unfamiliar, it's time to answer the second question regarding how home networks compare to larger networks like those in an office. Actually, the typical home network is very similar to an office network, but in a generally simpler, friendlier, and far less expensive package. That is, a home network still allows your PCs to talk to each other and share things such as files, printers, and Internet connections, but the manufacturers of home networking gear, such as Linksys, have concentrated on reducing the complexity so that you don't have to be an engineer to make it all work. In addition, home networks typically use a much simpler security model that doesn't require you to put up with complications like usernames, passwords, and deciding who gets to share what (unless you want to).
How Networks Really Work Computers aren't people, but they still communicate on a network similar to how a group of people communicates. That is, computers send out information that is addressed to a particular individual and then wait for a response that tells them that the message was successfully received. PCs perform this task quickly, and that's part of what makes networks so practical.
To get a better understanding of the process, imagine that Sarah is working on a homework assignment on the PC in her room. When she completes her book report, she needs a printed copy, but she doesn't have a printer connected to her PC. A printer is connected to the PC in the den, and she can use it to print out her report. The conversation between the PCs goes something like this:
"Hello den computer, this is Sarah's PC. I'm sending you this report to print."
"Okay, Sarah's PC, this is the den PC. I received the data and sent it to my printer."
Sure, that exchange sounds trivial, but it does provide a nutshell description of what's going on, as further illustrated by
Figure 1-3. At a basic level, a network functions quite simply by sending different messages as needed. The information in those messages—the data—can be something like Sarah's book report, digital images from your recent vacation, music files that you've saved on one of your PCs, or whatever other types of information you want to share.
Figure 1-3. The PCs on Your Home Network Talk to Each Other Through the Network
Things are more complicated inside the inner workings of the network. In Sarah's case, for example, the printer and the den PC actually engage in quite a bit of additional conversation, discussing whether the printer is out of paper, how many pages have finished printing so far, and details of what other reports the printer has been asked to print recently. Just like the telephone network, your computer network has to keep track of who is supposed to get each bit of information and make sure that everyone else isn't drowned by a sea of data that's not intended for them. Fortunately, your network automatically handles this additional complication, and you don't have to worry about it.
A Network Really Isn't Too Complicated for You
Setting up your own home network probably sounds like a great idea, but you might still have some doubts about whether it's really something that you can do. That's understandable, especially if you've heard horror stories about how difficult and complicated anything related to networks can be.
Well, don't believe those stories. The honest truth is that if you're willing to follow some simple directions, you can choose the proper equipment and install your own home network. You can then enjoy the benefits of having your own network without depending on someone else to make sure it all works, and if something goes wrong in the future, you'll know how to fix it. You really can do it yourself!
Article Source: Home Networking: A Visual Do-It-Yourself Guide
By Brian Underdahl
Keyboards and tradition monitors are both examples of simplex devices. The keyboard can only introduce input; the monitor can only accept output. 
The half-duplex mode is like one-lane road whit two-directional traffic. While cars are traveling one direction, cars going the other way must wait. In a half-duplex transmission, the entire capacity of a channel is taken over by whichever of the two devices is transmitting at the time.
The full-duplex mode is like a two-way street with traffic flowing in both directions at the same time. In full-duplex mode, signals going in either direction share the capacity of the link. This sharing can occur in two ways: Either the link must contain two physically separate transmission paths, one for sending and the other for receiving; or the capacity of the channel is divided between signals traveling in both directions. 
