What Makes Up a Network?
A network typically includes four things (besides the computers themselves):

Protocol: a set of communication rules to make sure that everyone speaks the
same language

Network interface cards (NICs): cards that plugs into the back (or side) of your
computers and lets them send and receive messages from other computers

Cable: the medium to connect all of the computers together

Router/Hub: hardware to perform traffic control
Note: The key word is "typically." Wireless networks obviously don't use cables and
NICs aren't necessary for small networks that use parallel/serial ports. Some networks use
switches, rather than hubs, to control the network. But the basics still apply.)
How Does a Network Work?
How does one computer send information to another? It is rather simple. The diagram
below shows a simple network:
“Visual Networking Overview – A Simple Network”. About.com. Web. New York:New York Times, 2010. September 7, 2010 <
http://compnetworking.about.com/od/basicnetworkingconcepts/l/blbasics_networ.htm>
If Computer 1 wants to send a file to Computer 2, the following would take place:
Based on a protocol that both computers use, the NIC in Computer A translates the file
(which consists of binary data -- 1's and 0's) into pulses of electricity.
The pulses of electricity pass through the cable with a minimum (hopefully) of resistance.
The hub takes in the electric pulses and shoots them out to all of the other cables.
Computer B's NIC interprets the pulses and decides if the message is for it or not. In this
case, it is, so Computer B's NIC translates the pulses back into the 1's and 0's that make
up the file.
Sounds easy. However, if anything untoward happens along the way, you have a
problem, not a network. So, if Computer A sends the message to the network using
NetBEUI, a Microsoft protocol, but Computer B only understands the TCP/ IP protocol,
it will not understand the message, no matter how many times Computer A sends it.
Computer B also won't get the message if the cable is getting interference from the
fluorescent lights, or if the network card has decided not to turn on today, etc.
Network Classification
Like snowflakes, no two networks are alike. So for the sake of discussion, it helps to
classify them by some general characteristics. A given network can be characterized by
its:

Size: the geographic size of the network

Security and access: who can access the network and how access is controlled

Protocol: the rules of communication in use on it (for example, TCP/IP,
NetBEUI, or AppleTalk)

Hardware: the types of physical links and hardware that connect the network

Size (LANs and WANs): regarding size, networks are generally lumped into two
categories, local area networks (LANs) and wide area networks (WANs)
A LAN is primarily defined by geography, and is typically housed in one building or
campus. A WAN, on the other hand, is a network that joins many LANs together using
super special, highly secret, WAN technologies, but we will delve into that arena some
other day. Hopefully you're still reading. Because they are so common, LANs are usually
further divided into two major types:

Peer-to-peer: A peer-to-peer network doesn't have any dedicated servers or
hierarchy among the computers. All of the computers on the network handle
security and administration for themselves. The users must make the decisions
about who gets access to what. For more information, see article Networking 101:
Peer-to-Peer Networks .

Client-server: A client-server network works the same way as a peer-to-peer
network except that there is at least one computer that is dedicated as a server.
The server stores files for sharing, controls access to the printer, and generally
acts as the dictator of the network. For more information, see article Networking
101: Client-Server Networks .
Protocol
As stated above, the protocol of a network is the set of guidelines for inter-computer
communication. Two computers with different protocols won't be able to communicate
with one another (imagine Ralph Nader and Pat Buchanan in the same room). While
many computers have the ability to interpret multiple protocols, it is important to
understand the different protocols available before deciding on one that is appropriate for
your network.
Peer-to-peer (P2P) networking eliminates the need for central servers, allowing all
computers to communicate and share resources as equals. Music file sharing, instant
messaging and other popular network applications rely on P2P technology.
Hardware
While some theoretically-minded people would claim that the hardware involved in a
network isn't extremely important, they probably haven't ever actually dealt with setting
one up. Hardware is important. While in theory, every hub or switch should send and
receive signals perfectly, that isn't always the case. And the problem is that if you ask two
network administrators what hub they recommend, you will probably get two entirely
different, yet passionate answers. From picking the cable (optical fiber, coaxial, or
copper), to choosing a server, you should find the most suitable hardware for your needs.
How do Wireless Networks work?
The key innovation behind wireless networking is that instead of using wires, they exploit
radio waves to send data between computers. That's the simple description. However, if
you wish to know more details about wireless networks, read on.
Ones and Zeros
As you surely know, digital data transmission occurs using binary: ones and zeros. This
communication method is easily applied to radio waves, as computers are able to send
out ones and zeros as different beeps. These beeps are actually so quick that human
beings cannot even hear them - as a matter of fact, we are constantly surrounded by radio
waves we simply can't hear. This fact, however, doesn't stop a computer from making use
of them.
Morse Code
The principle behind it is similar to the Morse code. As you may know, through this code
we can represent the alphabet in such a way that that it will be transmittable through the
radio using either a short beep called dot, or a long dash. First used manually, the code
became an effective way of sending information around with the development of the
telegraph. However, what's even more important is that it is actually a binary system like
a computer's ones and zeros.
Therefore, wireless networking can be though of as being similar to the Morse code for
computers. After plugging a combo radio receiver and transmitter in so the computer is
capable of transmitting its equivalent of dots and dashes (in this case, bits) to send your
data from here to there.
All About Frequencies
How can a computer be able to transmit enough bits to send and receive data at such a
fast speed? Shouldn't it have a maximum amount of data it can send in a second before it
just becomes ineffective? Well, the answer lies in the fact that wireless networking can
simply overcome this problem.
First, extremely high frequencies are used to send wireless transmissions, so that a lot
more data can be transmitted every second. The most commonly used frequency is that of
2.4 gig hertz (2.4 billion cycles per second), almost the same as what mobile phones and
microwave ovens use. However, such a high frequency requires a very short wavelength.
This is actually the reason why wireless networking can work only within a limited area.
Moreover, wireless networks use a technique we call 'frequency hopping'. By using many
frequencies in a certain range, they are able to always switch between them. Using more
than one frequency allows wireless networks to be more protected against interference
caused by other radio signals.
Access Points
The last step refers to all the computers on a network sharing Internet access made
possible by using a particular wireless device called wireless access points .
Since access points have radios that can communicate to approximately 100 computers
simultaneously and share Internet access between them, these pieces are more expensive
than wireless cards for one single computer. Because dedicated wireless access points are
necessary mostly for bigger networks, if you have only a few computers, use either one
of them as the access point or just buy a wireless router.
TCP/IP is arguably the single most important computer networking technology. The
Internet and most home networks support TCP/IP as the "language" computers use to
find and connect with each other.
IP addresses are the fundamental method for computers to identify themselves on most
computer networks. Every computer (or other network device) connected to the Internet
has an IP address.
This address, known as “IP address”, as “IP number”, or merely as “IP” is a code made
up of numbers separated by three dots that identifies a particular computer on the
Internet. These addresses are actually 32-bit binary numbers, consisting of the two
subaddresses (identifiers) mentioned above which, respectively, identify the network and
the host to the network, with an imaginary boundary separating the two. An IP address is,
as such, generally shown as 4 octets of numbers from 0-255 represented in decimal form
instead of binary form.
Other Networking Technologies:
With VoIP - voice over IP - service, consumers enjoy the convenience of a cell phone
with the benefits of full Internet connectivity for telephony. The same Internet Protocol
(IP) technology used in conventional data networks can be used to transmit voice and fax.
Virtual Private Network
The Virtual Private Network - VPN - has attracted the attention of many organizations
looking to both expand their networking capabilities and reduce their costs.
The VPN can be found in workplaces and homes, where they allow employees to safely
log into company networks. Telecommuters and those who travel often find a VPN a
more convenient way to stay connected to the corporate intranet. No matter your current
involvement with VPNs, this is a good technology to know something about. This VPN
tutorial involves many interesting aspects of network protocol design, Internet security,
network service outsourcing, and technology standards.
What Exactly Is A VPN?
A VPN supplies network connectivity over a possibly long physical distance. In this
respect, a VPN is a form of Wide Area Network (WAN).
The key feature of a VPN, however, is its ability to use public networks like the Internet
rather than rely on private leased lines. VPN technologies implement restricted-access
networks that utilize the same cabling and routers as a public network, and they do so
without sacrificing features or basic security.
A VPN supports at least three different modes of use:
Remote access client connections
LAN-to-LAN internetworking
Controlled access within an intranet
What is a Firewall?
A network firewall guards a computer network against unauthorized incoming messages
or undesired outgoing messages. Network firewalls may be hardware devices, software
programs, or a combination of the two.
Bluetooth
Bluetooth wireless technology is a short-range communications technology intended to
replace the cables connecting portable and/or fixed devices while maintaining high levels
of security. The key features of Bluetooth technology are robustness, low power, and low
cost. The Bluetooth specification defines a uniform structure for a wide range of devices
to connect and communicate with each other.
Bluetooth technology has achieved global acceptance such that any Bluetooth enabled
device, almost everywhere in the world, can connect to other Bluetooth enabled devices
in proximity. Bluetooth enabled electronic devices connect and communicate wirelessly
through short-range, ad hoc networks known as piconets. Each device can simultaneously
communicate with up to seven other devices within a single piconet. Each device can also
belong to several piconets simultaneously. Piconets are established dynamically and
automatically as Bluetooth enabled devices enter and leave radio proximity.
A fundamental Bluetooth wireless technology strength is the ability to simultaneously
handle both data and voice transmissions. This enables users to enjoy variety of
innovative solutions such as a hands-free headset for voice calls, printing and fax
capabilities, and synchronizing PDA, laptop, and mobile phone applications to name a
few