Local Area Network

A local area network (LAN) is a group of computers linked together over a relatively small area, generally within a business, institution, or residence; essentially, a LAN connects computers at high data speeds within one building or among a group of adjacent buildings. Users on a LAN can share files from computer to computer, tap into shared databases, and share expensive peripheral resources such as laser printers. LANs also allow users on the network to form private email groups and chat lists. Copper wires, coaxial cables, fiberoptic lines, or wireless radio-based technologies such as Bluetooth can be used to connect devices on a LAN.

A LAN can also be connected to other LANs outside its own small area, forming what is known as a wide area network, or WAN. This ability to interconnect made LANs one of the primary drivers in the growth of the early Internet. One could argue that the Internet itself is the world's ultimate WAN, comprising innumerable LANs that span the globe.

The history of the LAN runs parallel to the history of the Internet in some important ways, although the LAN's inventor, Bob Metcalfe, was trying to connect computers in different rooms, not different cities. In 1973, as a graduate student, Metcalfe was already a networking expert, and he was trying to earn his Ph.D. from Harvard University with a thesis examining the Internet's precursor, the ARPANET. He had some expertise in this area, having worked at the Massachusetts Institute of Technology (MIT), and built the interface between MIT's PDP-10 mainframe computer and the interface message processor (IMP, an early router) that connected MIT to the ARPANET. (According to Katie Hafner and Matthew Lyon in their 1996 book, Where Wizards Stay Up Late: The Origins of the Internet, Metcalfe offered to do the same thing for Harvard's PDP-10 but was denied the job on the premise that a mere graduate student could not possibly handle such a large and important task.) Metcalfe's thesis was rejected because it contained too much engineering and not enough theoretical science. The rejection was embarrassing, since Metcalfe had already accepted work at the Xerox Palo Alto Research Center (Xerox PARC), on the other side of the country.

Metcalfe stumbled upon a white paper by Norm Abramson, the architect of the radio-powered ALOHANET in Hawaii, which utilized APRANET's [Page 295]packet-switching technologies to connect computers wirelessly over relatively long distances. Abramson's paper, Metcalfe would later say, was “infuriating” because he thought it showed that ALOHANET was modeled on inaccurate math, manipulated to fulfill the designer's desired model. Then and there, Metcalfe determined to build a new and better network model based on ALOHANET. He traveled to the University of Hawaii, staying a month to study the radio system. Upon his return, he had the theoretical material that he needed to complete his Harvard thesis, and he had also taken the first steps toward inventing the LAN.

At the time, Xerox PARC was busy building the first personal computer, the Alto, and the company believed that people would want to connect these machines together. They assigned Metcalfe to the task of figuring out how this connecting could be done. He immediately faced two huge challenges: His network had to be fast enough to work with Xerox PARC's new laser printer, and it had to successfully bind together hundreds of computers within the same building, something that had never been done before.

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