Page 289 -

288 Part Two Information Technology Infrastructure

The range of frequencies that can be accommodated on a particular telecom-
munications channel is called its bandwidth. The bandwidth is the difference
between the highest and lowest frequencies that can be accommodated on a
single channel. The greater the range of frequencies, the greater the bandwidth
and the greater the channel’s transmission capacity.

7.3 THE GLOBAL INTERNET

We all use the Internet, and many of us can’t do without it. It’s become an
indispensable personal and business tool. But what exactly is the Internet? How
does it work, and what does Internet technology have to offer for business?
Let’s look at the most important Internet features.

WHAT IS THE INTERNET?

The Internet has become the world’s most extensive, public communication
system that now rivals the global telephone system in reach and range. It’s also
the world’s largest implementation of client/server computing and internet-
working, linking millions of individual networks all over the world. This global
network of networks began in the early 1970s as a U.S. Department of Defense
network to link scientists and university professors around the world.
Most homes and small businesses connect to the Internet by subscribing to an
Internet service provider. An Internet service provider (ISP) is a commercial
organization with a permanent connection to the Internet that sells temporary
connections to retail subscribers. EarthLink, NetZero, AT&T, and Time Warner
are ISPs. Individuals also connect to the Internet through their business firms,
universities, or research centers that have designated Internet domains.
There are a variety of services for ISP Internet connections. Connecting via
a traditional telephone line and modem, at a speed of 56.6 kilobits per second
(Kbps) used to be the most common form of connection worldwide, but it has
been largely replaced by broadband connections. Digital subscriber line, cable,
satellite Internet connections, and T lines provide these broadband services.
Digital subscriber line (DSL) technologies operate over existing telephone
lines to carry voice, data, and video at transmission rates ranging from 385 Kbps
all the way up to 40 Mbps, depending on usage patterns and distance. Cable
Internet connections provided by cable television vendors use digital cable
coaxial lines to deliver high-speed Internet access to homes and businesses. They
can provide high-speed access to the Internet of up to 50 Mbps, although most
providers offer service ranging from 1 Mbps to 6 Mbps. In areas where DSL and
cable services are unavailable, it is possible to access the Internet via satellite,
although some satellite Internet connections have slower upload speeds than
other broadband services.
T1 and T3 are international telephone standards for digital communication.
They are leased, dedicated lines suitable for businesses or government agencies
requiring high-speed guaranteed service levels. T1 lines offer guaranteed
delivery at 1.54 Mbps, and T3 lines offer delivery at 45 Mbps. The Internet does
not provide similar guaranteed service levels, but simply “best effort.”

INTERNET ADDRESSING AND ARCHITECTURE

The Internet is based on the TCP/IP networking protocol suite described earlier
in this chapter. Every computer on the Internet is assigned a unique Internet

MIS_13_Ch_07_Global.indd 288 1/17/2013 2:28:30 PM