Basic Concepts: Internetworks, Routers, and
Addresses
Bicycles with Motors
Data Link Addresses
Repeaters and Bridges
Routers
Network Addresses
Once upon a time, computing power and data storage were centralized. Mainframes were locked away in
climate-controlled, highly secure rooms, watched over by a priesthood of IS administrators. Contact with
a computer was typically accomplished by bringing a stack of Hollerith cards to the priests, who
interceded on our behalf with the Big Kahuna.
The advent of the minicomputer took the computers out of the IS temple of corporations and universities
and brought them to the departmental level. For a mere $100K or two, engineering and accounting and
any other department with a need for data processing could have their own machines.
Following on the heels of the minicomputers were microcomputers, bringing data processing right to the
desktop. Affordability and accessibility dropped from the departmental level to the individual level,
making the phrase personal computer part of everyone's vocabulary.
Desktop computing has evolved at a mind-boggling pace, but it was certainly not an immediate
alternative to centralized, mainframe-based computing. There was a ramping-up period in which both
software and hardware had to be developed to a level where personal computers could be taken seriously.