Glossary

Note: these aren't the definitions you'd find in a book. If that's what you want, then go look in a book. These are they way I would explain the terms to someone. I'd appreciate it if you'd let me know of anything that's misleading or just plain wrong, but I'm not trying to be too strict. Life is tough enough. Sometimes, I may show some sarcasm, though.

Firewall

A way to block unwanted traffic from a company's internal network. It can be as simple as a router that simply prohibits TCP/IP packets of a certain type from crossing the boundary between the company's LAN and the Internet. In a complex system, it will allow traffic only from certain IP addresses, or only certain kinds of traffic, or only traffic that has been authenticated somehow.

LAN

Local Area Network. It's a bunch of computers in reasonable physical proximity interconnected to each other, usually with 10baseT ethernet and a hub. A WAN is used to connect one LAN to another over a large distance.

Router

A Router can be either a box or some software that you run on a PC (Macs included, of course.) Routers are used as traffic directors between two networks, like between your local LAN and your ISP. For more details, see Routers and Hubs.

WAN

Wide Area Network. A network used to connect physically distance networks (LANS) together. The entire Internet can be thought of as a WAN. WANs generally involve telcos, like AT&T, carriers like UUnet or Qwest, frame relay or microwave links.