Thus, unlike traditional voice communications, packet switching does not require a single dedicated circuit between each pair of users.
Commercial packet networks were introduced in the 1970s, but these were designed principally to provide efficient access to remote computers by dedicated terminals.
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The Internet provides a capability so powerful and general that it can be used for almost any purpose that depends on information, and it is accessible by every individual who connects to one of its constituent networks.
It supports human communication via electronic mail (e-mail), “chat rooms,” newsgroups, and audio and video transmission and allows people to work collaboratively at many different locations.
Time-sharing systems allowed a computer’s resources to be shared in rapid succession with multiple users, cycling through the queue of users so quickly that the computer appeared dedicated to each user’s tasks despite the existence of many others accessing the system “simultaneously.” This led to the notion of sharing computer resources (called host computers or simply hosts) over an entire network.
Host-to-host interactions were envisioned, along with access to specialized resources (such as supercomputers and mass storage systems) and interactive access by remote users to the computational powers of time-sharing systems located elsewhere.
In 1974 Vinton Cerf, then at Stanford University in California, and this author, then at DARPA, collaborated on a paper that first described such a protocol and system architecture—namely, the transmission control protocol (TCP), which enabled different types of machines on networks all over the world to route and assemble data packets. By the early 1980s the “open architecture” of the TCP/IP approach was adopted and endorsed by many other researchers and eventually by technologists and businessmen around the world. While DARPA had played a seminal role in creating a small-scale version of the Internet among its researchers, NSF worked with DARPA to expand access to the entire scientific and academic community and to make TCP/IP the standard in all federally supported research networks.
TCP, which originally included the Internet protocol (IP), a global addressing mechanism that allowed routers to get data packets to their ultimate destination, formed the TCP/IP standard, which was adopted by the U. In 1985–86 NSF funded the first five supercomputing centres—at Princeton University, the University of Pittsburgh, the University of California, San Diego, the University of Illinois, and Cornell University.
However, time-sharing systems were then still too large, unwieldy, and costly to be mobile or even to exist outside a climate-controlled computing environment.
A strong motivation thus existed to connect the packet radio network to ARPANET in order to allow mobile users with simple terminals to access the time-sharing systems for which they had authorization.
NSF also funded various nonprofit local and regional networks to connect other users to the NSFNET.