[ Thanks to George for this link.
]
“If you are reading this article, you should have a good
understanding of how computers work and a working knowledge of how
to use Internet tools such as web browsers, Telnet, and e-mail. In
addition, you’re probably already aware of the need to protect
computers on your network from exterior threats, while still
allowing your web and e-mail traffic to traverse your connection to
the Internet. You may install a firewall to secure your network,
but to configure it correctly you must know just how your computer
connects to other computers and downloads web pages, exchanges
e-mail, or establishes a Telnet session. You’ll also need to know
how to set firewall rules to differentiate the legitimate network
traffic of your network users from the illicit access of hackers
and other external threats. As TCP/IP is the mechanism by which
your computer communicates with the rest of the Internet, you will
need to have more than a passing familiarity with it. This article
will give you a better idea of what is going on behind the scenes.
But why do you care how TCP/IP works if you aren’t a computer
programmer or network engineer? You should care, because the
hackers attempting to get past your network security often are
computer programmers or network engineers (self-taught or
otherwise), and in order to stop them you need to understand and
correct the weaknesses in TCP/IP or higher-level protocols that
they will attempt to exploit. In other words, know what your enemy
knows…”