ARPANET

The Advanced Research Projects Agency Network (ARPANET) was the first wide-area packet-switched network with distributed control and one of the first computer networks to implement the TCP/IP protocol suite. These technologies became the technical foundation of the Internet. The ARPANET was established by the Advanced Research Projects Agency (now DARPA) of the United States Department of Defense.

Building on the ideas of J. C. R. Licklider, Bob Taylor initiated the ARPANET project in 1966 to enable resource sharing between remote computers. The first computers were connected in 1969, and the network was declared operational in 1971. It quickly expanded, enabling early forms of email and file transfer.

In the early 1980s, ARPANET adopted Version 4 of TCP/IP, which allowed multiple networks to connect and form a network of networks. The ARPANET was formally decommissioned in 1990, after helping to create the worldwide network known today as the Internet.

Inspiration

The traditional telephone network used a system called circuit switching, where each call needed a direct connection. In the early 1960s, Paul Baran at the RAND Corporation proposed a new idea called distributed adaptive message block switching, meant to keep communications working even during attacks. Around the same time, Donald Davies at the National Physical Laboratory in the United Kingdom came up with a similar idea called packet switching.

In 1963, J. C. R. Licklider from Bolt Beranek and Newman wrote about a network for general communication among computer users, calling it the Intergalactic Computer Network. When he joined the Advanced Research Projects Agency, he encouraged others, like Ivan Sutherland and Bob Taylor, to develop this idea. Taylor saw that having one network could make it easier to connect to different computers instead of switching between them. Davies' work on packet switching influenced the development of the ARPANET, which became one of the first networks to use this technology.

Creation

In 1966, a man named Bob Taylor got money from the U.S. government to start a new kind of computer network called ARPANET. He hired Larry Roberts to help manage this project. They worked with many experts to decide how the network should work.

Finally, in 1969, a company called BBN built the first working version of ARPANET. It used small computers called Interface Message Processors to connect bigger computers together. This network helped computers talk to each other over long distances and was the beginning of what we now call the Internet.

Main article: ARPANET

Implementation

The first four nodes of the ARPANET were set up as a test to develop and debug the 1822 protocol. Though they were connected electronically in 1969, network applications couldn’t start until the Network Control Program was implemented in 1970. This program allowed the first two host-host protocols: remote login (Telnet) and file transfer (FTP). The network became operational in 1971, and traffic grew once email became common around 1973.

The first four hosts linked UCLA, ARC, UCSB, and the University of Utah School of Computing. The first node was at UCLA, where researcher Leonard Kleinrock could test network performance. The locations were chosen to save money on leased lines and because each had special expertise. The first successful connection was made between Stanford Research Institute (SRI) and UCLA on October 29, 1969. The first permanent link was set up on November 21, 1969. By December 5, 1969, the four-node network was complete.

The ARPANET kept growing. By 1970, it reached the East Coast of the United States. Over time, more IMPs (Interface Message Processors) were added, and the network expanded to include more university and government hosts. By 1973, there were 40 IMPs, and by 1975, the network had 57 IMPs. The network was shown at an international conference in October 1972.

Networking evolution

The ARPANET was the first wide-area network to use packet switching and distributed control. It was created by the Advanced Research Projects Agency of the United States Department of Defense. The network used special computers called IMPs to send messages between different computers. Early on, each IMP had a short number, and each computer connected to an IMP also had a small number. Together, these numbers made up an address that helped messages find their way to the right computer.

As the network grew, new ways to send messages were developed. One early method was called the 1822 protocol, which helped different kinds of computers talk to each other. Later, a new system called the Network Control Program (NCP) made it easier for many different programs on a computer to communicate over the network. Finally, researchers created a more advanced system called TCP/IP, which allowed many different kinds of networks to connect together. This became the foundation of the Internet we use today.

Main article: ARPANET

Operation

The ARPANET started as a research project focused on communication rather than direct user services. By 1975, control of the network moved to the Defense Communications Agency, and special devices were added to protect secret information. In 1981, the National Science Foundation helped expand access through the Computer Science Network.

Later, the ARPANET connected with networks in Norway and the UK, and by 1980, the Department of Defense chose TCP/IP as the main way for military computers to talk to each other. In 1984, the military created its own network called MILNET, which reduced the size of the ARPANET but kept it working for research purposes.

Applications

The ARPANET allowed different applications to share services on the same computer. This led to the creation of special rules, called application protocols, that worked separately from the network's basic services. Important protocols included TELNET for remote access and File Transfer Protocol (FTP) for sending files and early email.

In the 1970s and 1980s, new ways to send messages were developed. Ray Tomlinson created the first network e-mail in 1971, and soon email became a major part of ARPANET traffic. Later, Simple Mail Transfer Protocol, POP, and IMAP improved how email worked. Although attempts were made to enable voice calls through the Network Voice Protocol, they were not successful at the time.

Security

The ARPANET, the first wide-area computer network, needed ways to keep information safe. In 1971, a special method called the Purdy Polynomial was created to help protect passwords. This method used complex math to create a unique code for each password. Later, a big tech company named Digital Equipment Corporation used this same method to protect passwords in their VMS operating system, and it’s still used today for that purpose.

Main article: [Purdy Polynomial]

Rules and etiquette

Because the ARPANET was funded by the government, there were rules about how it could be used. Personal messages between users were allowed, but using the network for business or political purposes was not permitted.

One early example of breaking these rules happened in 1978 when Gary Thuerk from Digital Equipment Corporation sent the first mass email to many potential clients. This showed the power of using email for marketing, even though it wasn't allowed at the time. The network had strict guidelines to ensure it was used only for government-related work.

Decommissioning

In 1985, a new project called NSFNET was created to help universities and government agencies connect to each other. By 1990, the ARPANET, the very first network that helped start the Internet, was turned off. Some of its old machines were still used until July of that year.

When the ARPANET was shut down on February 28, 1990, Vinton Cerf, a leader in Internet development, wrote a poem to honor it. He called it "Requiem of the ARPANET," remembering the ARPANET’s important role in creating the Internet we use today.

Legacy

The ARPANET was very important for the development of modern computer networking, including the Internet. It introduced new ideas like packet switching and decentralized networks, which helped create a global network that changed how we communicate and share information.

Many research projects were connected to the ARPANET, either influencing its design or coming from it. Senator Al Gore helped pass a bill in 1991 that supported the growth of the National Information Infrastructure, which he called the information superhighway. The ARPANET was recognized with two IEEE Milestones in 2009. In 2011, a historical marker was placed in Arlington County, Virginia, to honor the early roots of the Internet.