Introduction - Java Software Solutions: Foundations of Program Design - page 23

The impact of networks on computer systems has been dramatic. Computing
resources can now be shared among many users, and computer-based commu-
nication across the entire world is common. In fact, the use of networks is now
so pervasive that some computers require network resources in order to operate.

The Internet
Throughout the 1970s, an agency in the Department of Defense known as the
Advanced Research Projects Agency (ARPA) funded several projects to explore
network technology. One result of these efforts was the ARPANET, a WAN that
eventually became known as the Internet. The Internet is a network of networks.
The term Internet comes from the WAN concept of internetworking —connecting
many smaller networks together.
From the late 1980s through the present day, the Internet has
grown incredibly. In 1983, there were fewer than 600 computers
connected to the Internet. At the present time, the Internet serves
billions of users worldwide. As more and more computers con-
nect to the Internet, the task of keeping up with the larger number of users
and heavier traffic has been difficult. New technologies have replaced the
ARPANET several times since the initial development, each time providing more
capacity and faster processing.
A protocol is a set of rules that governs how two things communicate. The
software that controls the movement of messages across the Internet must con-
form to a set of protocols called TCP/IP (pronounced by spelling out the let-
ters, T-C-P-I-P). TCP stands for Transmission Control Protocol, and IP stands
for Internet Protocol. The IP software defines how information is formatted
and transferred from the source to the destination. The TCP software handles
problems such as pieces of information arriving out of their original order or
information getting lost, which can happen if too much information converges
at one location at the same time.
Every computer connected to the Internet has an

KEY CONCEPT
The Internet is a wide-area network
(WAN) that spans the globe.

IP address that uniquely iden-
tifies it among all other computers on the Internet. An example of an IP address
is 204.192.116.2. Fortunately, the users of the Internet rarely have
to deal with IP addresses. The Internet allows each computer to be
given a name. Like IP addresses, the names must be unique. The
Internet name of a computer is often referred to as its

KEY CONCEPT
Every computer connected to the
Internet has an IP address that
uniquely identifies it.

Internet

address. An example of Internet address is hector.vt.edu.
The first part of an Internet address is the local name of a specific computer.
The rest of the address is the domain name, which indicates the organization to
which the computer belongs. For example, vt.edu is the domain name for the
network of computers at Virginia Tech, and hector is the name of a particular