Networking

A network is a communications system for connecting end systems called hosts. The mechanisms of connection might be copper wire, ethernet, fiber optic or wireless, but that won't concern us here. A local area network (LAN) connects computers that are close together, typically belonging to a home, small organization or part of a larger organization.

A Wide Area Network (WAN) connects computers across a larger physical area, such as between cities. There are other types as well, such as MANs (Metropolitan Area Network), PANs (Personal Area Networks) and even BANs (Body Area Network).

An internet is a connection of two or more distinct networks, typically LANs or WANs. An intranet is an internet with all networks belonging to a single organization.

There are significant differences between an internet and an intranet. Typically an intranet will be under a single administrative control, which will impose a single set of coherent policies. An internet on the other hand will not be under the control of a single body, and the controls exercised over different parts may not even be compatible.

A trivial example of such differences is that an intranet will often be restricted to computers by a small number of vendors running a standardized version of a particular operating system. On the other hand, an internet will often have a smorgasbord of different computers and operating systems.

The techniques of this book will be applicable to internets. They will also be valid for intranets, but there you will also find specialized, non-portable systems.

And then there is the "mother" of all internets: The Internet. This is just a very, very large internet that connects us to Google, my computer to your computer and so on.