ARPANET Protocols

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).

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.

In the next section, we'll learn about some of the tasks ARPANET made possible for the first time.