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How ARPANET Works


ARPANET Breakthroughs

ARPANET allowed people to do things with computers that had never been done before or were only possible on a much smaller scale, including:

  • Remote logins: With ARPANET, people could use one computer system to log into another one miles away. For the first time, researchers and scientists could access databases full of information without having to physically travel to another computer site. In 1971, ARPANET integrated the first Terminal Interface Processor (TIP), which enabled users at individual computer terminals to dial into the network [source: Living Internet].
  • File transfers: Users could access information in other computer systems as well as copy and save data or send files across the network. By the fall of 1970, ARPA had upgraded the IMP software package so that each IMP could download new software from the other IMPs. From then on, ARPA could make upgrades to the system through one IMP, which would send the upgrades to every other IMP in the system.
  • E-mail: In 1972, programmer Ray Tomlinson developed an electronic mail system for ARPANET by adapting a pair of Tenex operating system applications called SNDMSG and READMAIL. Tomlinson chose the "@" symbol to join together the names of the recipient and the recipient's host computer, a convention we still use today.

Shortly after e-mail debuted on ARPANET, a few team members began to play around with mailing-list software applications. Soon someone on ARPANET could send out an e-mail message to a group of people in one step. Mailing lists focused on specific topics began to appear. The first was SF-LOVERS, a list that connected the science fiction fans on the ARPANET team. But ARPA frowned on people using the network for unofficial purposes and demanded that list owners dissolve all unauthorized mailing lists. Users later convinced ARPA to allow these lists by pointing out that they helped test the network's mail capacity [source: American Heritage Magazine].

In 1973, Robert Kahn initiated an experiment with a technique he called internetting -- combining two or more separate networks into a larger network. He began to look into ways to integrate ARPANET with the Defense Advanced Research Projects Agency's (DARPA) Packet Radio Network, which was a network that used radio waves to send data from one computer to another.

In 1983, ARPANET officially switched from NCP to the TCP/IP suite of protocols. Just as ARPANET's architecture and protocols foreshadowed the Internet's structure, the applications users created to navigate and interact with the network paved the way for many of today's Internet features.

In the next section, we'll look at the end of the ARPANET projects.


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