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Protecting Your Data: A Guide to Windows Firewall


CHAPTER 2: NETWORKING BASICS


To understand the operation of a firewall, you must also understand the basics of network communication. Although most people consider the network to be mysterious and complex, it's actually a very structured, standardized, and logical grouping of protocols. In this guide, we'll provide an overview of computer networking and show how the network is related to firewalls and applications.


Internet Protocol (IP)
There are millions of devices on the Internet, and they can all communicate with each other. That fact alone is impressive, especially considering the Internet's growth and diversity. Our network communications traverse high-speed backbones between our major cities, navigate paths under the ocean, and travel into outer-space on satellite-based links. Through it all, our Internet communication remains active and available.

The secret to this robust networking capability is the underlying networking protocols. The creators of these protocols built the system to provide reliable communication regardless of the circumstances. It doesn't matter if you're on a dial-up link, a high-speed broadband connection, or on a satellite link in a remote country - the network protocol is always the same.

This universal functionality is based on a protocol that's aptly named the Internet Protocol (IP). Every system on the Internet is assigned an IP address, and these IP addresses are used to move packets of information from one side of the Internet to the other. If you don't have an IP address, then you can't communicate on the Internet!

An IP address is similar to a postal address. If someone wants to send you a letter, they must use the appropriate mailing address. A sender includes their return address so the receiver recognizes the source of the letter without opening the envelope. Like an IP address, a postal address allows you to communicate with anyone in the world using this standard method of communication.

In Windows XP, your IP address remains hidden from view during normal operation. If you'd like to view your IP address, select your network or dial-up adapter in the Control Panel / Network Connections (or Network and Internet Connections / Network Connections) section. Your IP address information is contained under the Support tab of the network adapter's status dialog box. The IP address consists of four numbers separated by periods (or "dots").


For the purposes of this document, it's only important to know that the IP address exists. A comprehensive knowledge of the IP protocol and its extensive functionality aren't necessary to understand Windows Firewall.

On most systems, the IP address is assigned automatically and it's normal for the address to change over time. On dial-up networks, a different IP address is usually assigned each time a connection is established. You'll also find that your wired Ethernet adapter may use one IP address and your wireless network adapter may use a different IP address.