The Internet, sometimes called simply "the Net," is a worldwide
system of computer networks - a network of networks in which users at
any one computer can, if they have permission, get information from
any other computer (and sometimes talk directly to users at other
computers).
It was conceived by the Advanced Research Projects Agency (ARPA) of
the U.S. government in 1969 and was first known as the ARPANET. The
original aim was to create a network that would allow users of a
research computer at one university to be able to "talk to" research
computers at other universities. A side benefit of ARPANet's design
was that, because messages could be routed or rerouted in more than
one direction, the network could continue to function even if parts of
it were destroyed in the event of a military attack or other disaster.
Internet Addresses
Each computer connected to the Internet has a unique address.
Internet addresses are in the form ###.###.###.### where ### must be a
number from 0 - 255. This address is known as an IP address. (IP
stands for Internet Protocol)
If you connect to the Internet through an Internet Service Provider
(ISP), you are usually assigned a temporary IP address for the
duration of your dial-in session. If you connect to the Internet from
a local area network (LAN) your computer might have a permanent IP
address or it might obtain a temporary one from a DHCP (Dynamic Host
Configuration Protocol) server. In any case, if you are connected to
the Internet, your computer has a unique IP address.
So how does one computer 'talk' to other computers connected to the
Internet? Let's say your IP address is 1.2.3.4 and you want to send a
message to the computer 5.6.7.8. The message you want to send is
"Hello computer 5.6.7.8!". Let's say you've dialed into your ISP from
home and the message must be transmitted over the phone line.
Therefore the message must be translated from alphabetic text into
electronic signals, transmitted over the Internet, and then translated
back into alphabetic text.
Language of the Internet
This is accomplished through a set of rules or protocol stack.
Every computer needs one to communicate on the Internet and it is
usually built into the computer's operating system (i.e. Windows,
Unix, etc.). The protocol stack used on the Internet is referred to as
the TCP/IP protocol stack because of the two major communication
protocols used.
Internet Infrastructure
So now you know how packets travel from one computer to another
over the Internet. But what's in-between? What actually makes up the
Internet? Please refer to diagram Internet Infrastructure. The
physical connection through the phone network to the Internet Service
Provider might have been easy to guess, but beyond that might bear
some explanation.
The ISP maintains a pool of modems for their
dial-in customers. This is managed by some form of computer (usually a
dedicated one), which controls data flow from the modem pool to a
backbone or dedicated line router. This setup may be referred to as a
port server, as it 'serves' access to the network. Billing and usage
information is usually collected here as well.
After your packets traverse the phone network and your ISP's local
equipment, they are routed onto the ISP's backbone or a backbone the
ISP buys bandwidth from. From here the packets will usually journey
through several routers and over several backbones, dedicated lines,
and other networks until they find their destination, the computer
with address 5.6.7.8.
More Links About the Internet &
World Wide Web
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