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The Internet's address architecture is
implemented in IP. IP's original addressing scheme dates back to the early
1980s. At the time, the Internet itself was little more than a semi-public
network that interconnected a few dozen universities, research
organizations, and government bodies. Each of these entities that
connected to the Internet had limited networked computing infrastructures.
Typically, these infrastructures consisted of little more than a mainframe
computer or a handful of UNIX-based minicomputers. PC applications had yet
to mature to a level that was useable in business, and local-area networks
(LANs) were in their infancy. Therefore, an internetwork did not require a highly scalable
architecture.
The original Internet was given a
relatively simple, but compact, two-level hierarchy. The top level was the
Internet itself, and the bottom level was the collection of individual
networks, with their hosts, that were interconnected via the Internet. This hierarchy is
illustrated in the main figure.
The Internet's simple --- but powerful and
extensible --- architecture served its user community well.
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