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11 Glossary of terms
LAN – Local Area Network
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 large
areas. 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 are CAT5 and CAT 6 cables
(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 10/100Mbps network
card, or a wireless network card. Most networks use hardware devices such as hubs or switches
that each cable can be connected to in order to continue the connection between computers. A
hub simply takes any data arriving through each port and forwards the data to all other ports. A
switch is more sophisticated, in that a switch can determine the destination port for a specific
piece of data. A switch minimizes network traffic overhead and speeds up the communication
over a network.
What is Router?
A router is a device that forwards data packets from a source to a destination. Routers forward
data packets using IP addresses and not a MAC address. A router will forward data from the
Internet to a particular computer on your LAN. A router also determines the best route that data
packets should follow to ensure that the data packets are delivered properly.
Firewall
A firewall is a device that sits between your computer and the Internet that prevents
unauthorized access to or from your network. A firewall can be a computer using firewall
software or a special piece of hardware built specifically to act as a firewall. In most
circumstances, a firewall is used to prevent unauthorized Internet users from accessing private
networks or 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.
VPN – Virtual Private Network
Virtual Private Networking (VPN) uses a publicly wired network (the Internet) to securely
connect two different networks as if they were the same network. For example, an employee
can access the corporate network from home using VPN, allowing the employee to access files
and printers. Below are several different implementations of VPN that can be used.
PPTP – Point-to-Point Tunneling Protocol
PPTP uses proprietary means of connecting two private networks over the Internet. PPTP is a
way of securing the information that is communicated between networks. PPTP secures
information by encrypting the data inside of a packet.
