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Internet Security and Privacy
60 McAfee Guard Dog
Why packets?
Why go through all this trouble, breaking data down into packets? The answer
lies in the origins of TCP/IP. TCP/IP, like the Internet itself, is a product of the
Cold War. Originally developed by the United States Department of Defense,
the Internet was designed to ensure secure communications, even with the
multiple communications network failures anticipated during nuclear war.
TCP/IP solves the problem of network failure by assuming that a certain
amount of noise always exists in the network: Noise may be random data
errors or more serious system crashes. If you have ever tried to speak in a noisy
room, you know the necessity of repeating yourself—and that is exactly what
TCP/IP is designed to do. Breaking data down into packets allows the Internet
to seek alternate routes if one route is inaccessible. If a packet cannot get
through or arrives damaged, the receiving computer simply requests it again
until it arrives successfully.
When you send an e-mail message, for example, it is broken into several
packets. Depending on how noisy the network is, each packet may need to be
routed over a separate route in order to find its way to its destination.
Furthermore, network problems may cause some of the packets to be delayed
so they arrive out of order. To compensate, TCP examines each packet as it
arrives to verify that it's OK. Once all the packets are received, TCP puts them
back in their original order. Of course, all of this happens quickly and
automatically, so you will never see the process at work.
The Internet and the Web…what is the difference?
Before the Web, the Internet was mostly command-line driven, and
character-based: You had to type in the exact Internet address of the place you
wanted to go at a command line. In 1989, Tim Berners-Lee of the European
Particle Physics Laboratory proposed a new way to share information over the
Internet. The essential feature in Berner-Lee’s vision of the Web is that it links
documents together. When you click a link on a Web page, you are
automatically connected to another Web site. This linking function, combined
with the increasing graphics abilities of home computers, transformed the
Internet into a graphically rich place, complete with video, sound, and
pictures. By linking information together in a graphically-appealing package,
the Web made the Internet more attractive to the typical consumer.
The Internet is a network of linked computers that uses TCP/IP as its
underlying messaging system. The World Wide Web (WWW, or just “Web”
for short) is hosted by the Internet, and is an ever-expanding collection of
documents employing a special coding scheme named Hypertext Markup
Language (HTML).