built specifically to act as a firewall. In most circumstances, a firewall is used to prevent unauthorized Internet users from accessing private networks such as corporate LAN’s and Intranets.
A firewall watches all of the information moving to and from your network and analyzes each piece of data. Each piece of data is checked against a set of criteria that the administrator configures. If any data does not meet the criteria, that data is blocked and discarded. If the data meets the criteria, the data is passed through. This method is called packet filtering.
A firewall can also run specific security functions based on the type of application or type of port that is being used. For example, a firewall can be configured to work with an FTP or Telnet server. Or a firewall can be configured to work with specific UDP or TCP ports to allow certain applications or games to work properly over the Internet.
Introduction to Local Area Networking
Local Area Networking (LAN) is the term used when connecting several computers together over a small area such as a building or group of buildings. LAN’s can be connected over a large area. A collection of LAN’s connected over a large area is called a Wide Area Network (WAN).
A LAN consists of multiple computers connected to each other. There are many types of media that can connect computers together. The most common media is CAT5 (Ethernet) cable; UTP or STP twisted pair wire. On the other hand, wireless networks do not use wires; instead they communicate over radio waves. Each computer must have a Network Interface Card (NIC), which communicates the data between computers. A NIC is usually a 10Mbps network card, or 10/100Mbps network card, or
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