What is ARPANET?

We rely on the modern Internet for communication, sharing, learning, and much more. But most people don’t know how the Internet came to be. Though the contemporary Internet originated in the 1990s, the predecessor to the Internet – known as ARPANET – existed years prior. In this article, take a closer look at the history of ARPANET and learn about its influence on the development of the Internet as we know it today.

ARPANET definition

ARPANET, or Advanced Research Projects Agency Network, was an early packet-switching network and the first to implement the TCP/IP protocol suite. Established in 1969 by the U.S. Department of Defense, ARPANET was the precursor to the modern internet and played a significant role in developing today’s networking technologies.

How did it work?

ARPANET utilized many technologies, including the TCP/IP protocol, interface message processors, and packet switching. Here’s how each of ARPANET’s main components worked.

Packet switching

Packet switching was the key concept that enabled ARPANET’s operation. Here’s how it worked:

• The data transmitted between two computers was broken down into smaller units called packets.
• Each packet contained a portion of the data with information about its destination.
• The packets were transmitted individually across the network and routed independently based on the addressing information.

The packet-switching approach helped organizations improve their use of computing resources with multiple packets sent and received simultaneously.

TCP/IP Protocol

TCP, which replaced the earlier NCP protocol, was vital in enabling more reliable communication over ARPANET. The main functions of TCP/IP were:

• Providing reliable data transmission between multiple computers connected to the network.
• Introducing flow control mechanisms that prevented data overflow and network congestion.
• Checking for errors to ensure the integrity of the received data and prevent the transmission of corrupt data packets.
• Providing more flexibility than the previously used NCP protocol, like working with different types of networks and devices.

These and several other TCP functions allowed computer terminals to communicate and exchange information on ARPANET.

Interface message processors

Interface message processors (IMPs) were important components of ARPANET, serving as intermediaries between host computers and the network. Here’s how they worked:

• IMPs were specialized computers designed to connect the host computers and the ARPANET network. Each host computer had a dedicated IMP responsible for transmitting and receiving data packets.
• The interface message processors acted as gateways. They translated data from the host computers into packets to be transmitted across the network. IMPs also added the necessary information to data packets and ensured they were correctly routed to their destinations.
• When a host computer wanted to send data, it would send it to its dedicated IMP. The IMP would break the data into packets, add appropriate information (e.g., headers) and transmit them.
• The receiving interface message processor would strip off the headers and deliver the data to the host computer.

Overall, the IMPs acted as important intermediaries in the ARPANET communication process.

ARPANET evolves into the Internet

In the first half of the 1980s, the Defense Advanced Research Projects Agency (DARPA) started developing a new protocol suite called TCP/IP, designed to replace the Network Control Program (NCP) used in ARPANET. TCP/IP was essentially a networking protocol that allowed different networks to communicate with each other. It was this development that helped pave the way for the transformation of ARPANET into what we now call the Internet.

The Internet continued to grow rapidly in the United States. By the late 1980s, it was clear that the Internet had become an essential communication tool. The emergence of email, file sharing, and bulletin board systems all provided further impetus for the expanding Internet.

The Internet’s transformation from ARPANET into the current global network occurred thanks to several key factors, including:

• Better technologies. Advanced protocols like TCP/IP allowed different networks to communicate which led to the development of the Internet.
• Increased collaboration. The networking community worked hand-in-hand across institutions and organizations to bring the Internet to life.
• Increased funding. The US government provided increased funding for network research and development, which helped accelerate the growth of the Internet.
• Rapid technological advancements. Advancements in computer hardware and software, including personal computers, led to increased demand for networking capabilities.

Conclusion

Taking a closer look at ARPANET’s history enables us to better understand how certain modern technologies work today. From the idea that there needed to be a network that could save critical data in case of a nuclear attack, the creators of ARPANET provided us with so much more.

This technology has been a game-changer. Even though it took a few decades for ARPANET to fully transform into the internet, humanity should be forever thankful to the pioneers who paved the way for a better life and more efficient business transactions. From managing to connect several computers during the past century, we’ve reached a point where we’re able to schedule doctor’s appointments online, video chat with friends 5,000 miles away, and even use face recognition software to unlock our phones and laptops.