How the first computer network came to life?

Why was the need for networks first realized?

It was 1960s and the cold war was at its peak. USA and the USSR were fiercely competing with each other in space, defense and technology. So the US created ARPA(Advanced Research Project Agency) for advancing research on critical technologies. Back then there was a fear that if the USSR destroyed the Central Military Command of the US there must be an alternative. That alternative was to create a more decentralized network of commands where even if the central command was destroyed the information can flow through other paths. Other main reason for something like this was also to facilitate greater communication and collaboration between universities and labs.

So the ARPA(now DARPA) was tasked with coming up with a solution for this and that is how ARPANET the first network came to life in 1969.

What was this ARPANET?

ARPANET was the first operational packet switching network. Initially it was setup at 4 places, we can call them 4 nodes. These 4 nodes were UCLA, Stanford Research Institute, UCSB and the University of Utah. First ever communication through ARPANET was established between UCLA and Stanford. They wanted to send “LOGIN“ from UCLA as the message but only “LO” was received at Stanford. They were connected via 56kbps line which is very weak and the system crashed after only “LO“ was received. But this was still a great leap and this was the first ever established communication performed through ARPANET.

Architecture of ARPANET

ARPANET basically was made up of two main components Host Computers or Mainframe Computers and IMPs(Internet Message Processor).

Host Computers were the big computers which the researchers and scientists used at universities. And IMPS can be considered as routers which passed the information further. In ARPANET every Host computer was connected to a IMP and later IMPs were connected to more IMPs like a mesh to relay information.

Above is the simplified diagram of the ARPANET architecture.

Suppose one Host wants to send a message to other Host. Then at first the message from the Host reaches the IMP. Now IMPs worked like a modern day router. The message when received by IMP was divided into multiple packets of data. Now the small packets of data found the best possible path through the IMPs network to reach the Host. But just before reaching the host, IMP used to reassemble all the packets of data into one and then passed this reassembled data to the receiver HOST. This is how communication was done through ARPANET. And the IMPs played a very crucial role in this. The IMPs were connected with each other through dedicated lines(also called leased lines). And through these lines data used to travel between IMPs.

ARPANET used NCP(Network Control Protocol) to establish this communication. Its just a set of rules of communication. And in 1983 it shifted to TCP(Transmission Control Protocol) which is still a very popular protocol today.

Why ARPANET was revolutionary?

ARPANET was truly revolutionary because for the first time it introduced packet switching. Before it circuit switching was used but it had many disadvantages. In circuit switching a dedicated path had to be established for each communication and had to be reserved during the entire communication. This was a lot of wastage of bandwidth. ARPANET solved this by introducing packet switching. In this system no dedicated lines were required for communication and multiple users can use the same line. It was also more resilient because if one route fails then packets can take the other route. It was also very fast when compared to circuit switching. These advantages of ARPANET made it a revolutionary milestone in technology.

What came after ARPANET?

ARPANET was the first network to implement the TCP/IP protocols which are still used prominently to this day. It also gave birth to email in 1970s which became very popular instantly.

Then in 1985 using the research of ARPANET a new network NSFNET(National Science Foundation Network) was created. It was a high speed network funded by US National Science Foundation. It quickly replaced ARPANET and by 1990 ARPANET was decommissioned. NSFNET quickly transitioned into global and open commercial internet. TCP/IP protocols were adopted worldwide. And in 1991 WWW(World Wide Web) was finally released. This was the beginning of the new age of internet. It added browsers and websites to the internet and created the form of internet which we know and use today daily.

Thank you hope you enjoyed reading and learned something. Stay curious