HTML and CSS Reference
you work in an office, you probably use a computer connected to a LAN. Recently, many
people have begun to set up LANs in their homes to share resources among computers. A
Metropolitan Area Network (MAN) connects users with computer resources in a geo-
graphical area. It also can be used to connect two or more LANs. A Wide Area Network
(WAN) is geographically dispersed and usually uses some form of public or commercial
communications network. For example, an organization with offices on both the East
and West Coasts of the United States probably uses a WAN to provide a link between the
LANs at each of the offices. See Figure 1.2 for a diagram of this connectivity.
A backbone is a high-capacity communication link that carries data gathered from
smaller links that interconnect with it. On the Internet, a backbone is a set of paths that
local or regional networks (MANs) connect to for long-distance interconnection. The
Internet is a group of interconnected networks with very high-speed connectivity pro-
vided by the Internet backbones. Figure 1.3 shows a commercial backbone network
map generated by http://www.caida.org/tools/visualization/mapnet/Backbones.