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LANs, WANs & topologies
A LAN is a network you could walk across (one office, one floor, one home) fast, cheap and under your control. A WAN stitches distant LANs together over links you rent rather than own. The internet is the biggest WAN of all: a federation of millions of LANs that agreed on one protocol family.
Topology is the shape of the wiring: star, mesh, ring. Modern LANs are almost always stars around a switch, but knowing the shapes explains why old networks failed in the ways they did.