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Education for all
Before we get started, I would like to define some terms and set some ground rules. For the purposes of this book (and your professional life, I hope), a computer network can be defined as “two or more computers connected by some means through
which they are capable of sharing information.” Don’t bother looking for that in an RFC because I just made it up, but it suits our needs just fine.
There are many types of networks: Local Area Networks (LANs), Wide Area Networks (WANs), Metropolitan Area Networks (MANs), Campus Area Networks (CANs), Ethernet networks, Token Ring networks, Fiber DistributedData Interface (FDDI) networks, Asynchronous Transfer Mode (ATM) networks, frame-relay networks, T1 networks, DS3 networks, bridged networks, routed networks, and point-to-point networks, to name a few. If you’re old enough to remember the program Laplink, which allowed you to copy files from one computer to another over a special parallel port cable, you can consider that connection a network as well. It
wasn’t very scalable (only two computers), or very fast, but it was a means of sending data from one computer to another via a connection.
The connection is an important concept. It’s what distinguishes a sneakernet, in which information is physically transferred from one computer to another via removable media, from a real network. When you slap a floppy disk into a computer, there is no indication that the files came from another computer—there is no connection. A connection involves some sort of address or identification of the nodes on the network (even if it’s just master/slave or primary/secondary).