ARPANET Protocols

Sputnik: The Internet's Grandpa In 1957, the Soviet Union launched Sputnik, the first manmade satellite, into orbit. For the people and government of the United States, it was a shocking moment -- suddenly the U.S. was no longer the most technologically advanced nation on the planet. In 1958, President Dwight D. Eisenhower created ARPA to encourage technological development in the U.S.

Most of us take the Internet for granted. We can log into our e-mail and browse the World Wide Web. But when the ARPANET project began, there were no procedures or systems in place to let different computers share information. Everything had to be invented from scratch.

One of the most important decisions the ARPANET team made was to create a standardized system of protocols that the host computers and IMPs would follow. A group called the Network Working Group formed to take on the job. At first, the creation process was chaotic and disjointed. The ARPANET team began to design and establish these protocols through its RFCs.

Early in the process, the team recognized the need for two specific tasks: Create a way for users to log in to the system remotely and make it possible to move files from one machine to another. Remote login later became known as Telnet, and moving files back and forth became part of the File Transfer Protocol (FTP). The team submitted these first two protocols to Larry Roberts, the head of the project. Roberts decided that the initial protocols weren't ambitious enough and told the team to include more functions and processes.

The team began to design the Network Control Program (NCP), a symmetric host-host protocol. In simpler terms, this was the procedure for allowing computers to communicate within the network as well as adding more hosts to the network to make it bigger. The NCP also controlled the path and flow of data over ARPANET. It established the practice of using numeric host addresses for network communication and was a forerunner to today's domain name servers (DNS).

Following Protocol

NCP provided the groundwork for Transmission Control Protocol/ Internet Protocol (TCP/IP) suite of Internet protocols. Robert Kahn and Vinton Cerf designed TCP/IP, which determines how information moves through the Internet and verifies that the information gets where it's going. Think of TCP/IP as a traffic control system -- without these protocols, computers wouldn't know which pathways were available and the entire network could crash.



ARPANET also took advantage of a revolutionary new way to send data: packet switching. In packet switching, host computers divide each computer file into smaller segments called packets. Once the packets are transferred, the pieces are reassembled into the original files.

Packet switching plays an enormously important role on the Internet today. Information can flow through the entire system much faster when computers break files into smaller pieces. That's because one huge file traveling through a pathway takes up a lot of bandwidth. Several smaller packets can travel through different paths within a network to the same destination. If part of a pathway is closed for some reason, the road-blocked packets can find another path while the rest of the information continues to load on the user's computer.

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.