The history of Internet evolution seen in the chronology

How has the Internet developed?First, let's take that history.

The origin of the Internet dates back to the experimental network "ARPANET", which was started in 1969 by the US Department of Defense.Initially, it was a network that connected four large computers at the University of California (UCSB), the Stanford Research Institute (SRI), the University of California, Los Angeles (UCLA), and the University of US Yuta University.A machine called "IMP" (Interface Message Processor) was used for the connection.It is the ancestor of the current router.

However, it is not a dedicated hardware product like today.Hanewell's general -purpose computer, "HANEYWELL 516", incorporates NCP (Network Control Program) for communication.US BBN was developed mainly.IMP was installed in the order of UCSB, SRI, UCLA, and Utah University.

各拠点の大型コンピュータは、拠点ごとに置かれたIMPにつないだ。それぞれのIMPの間は、米AT&Tの50kビット/秒の通信回線で互いに接続していた。大型コンピュータ同士がこのネットワークを経由して通信する。

The IMP already had the basic functions of the current router.For example, it is a function that always updates the route table indicating a packet transfer destination to the latest information.As a result, a packet can be delivered on another route even if a certain route cannot be used.It is the basis of the current dynamic routing.It also had functions such as checking errors, retransmission of packets, and flow control to avoid congestion.

The most important thing about Arpanet is that it is the world's first packet exchange network.So let's take a look at how packet replacement was born.

Until the packet exchange appeared, the communication technology of line exchange was the mainstream.This is a method that has been used over the phone for a long time.

A line exchange is a method that allows you to switch the line by switching the line using a machine called a replacement device to achieve many terminal communication with a small number of lines.However, when a specific terminal was communicating with each other, there was a problem that the line used in the communication was mixed and other terminals could not be used.The line is inefficient because the line is dedicated even when the data is not sent.There is also a problem that it is difficult to redundant communication because a fixed line is used.

To solve these problems, packets were born in the 1960s.In this method, the data is divided into a small unit called packet and passed it to the router.By handing the packet between the routers, the packet is delivered to the communication partner.Connect the packet on the side that received the data.

The advantage of this method is that different sources and destination packets can be sent on the same line.Unlike a line exchange in which a certain communication takes a line, multiple communications can be used efficiently because multiple communications share the line.In addition, the address may be sent the same packet in a different route.As a result, the communication path can be easily redundant.

The idea of packet exchange was devised separately by US researcher Paul Balan and British physicist Donald Davis.

Balan was a think tank that studies military strategies, studying networks that can maintain communication functions even if they are attacked.As a result, he came up with packet replacement and autonomous distribution network.In such a method, even if a route cannot be used by attack, you can switch to another route to continue communication.

At about the same time, Davis came up with an idea of packet exchange.However, the purpose is not a military, but the efficiency of the line.At that time, the computer was expensive, so it was common to have a time -sharing system (TSS) in which multiple users share computers.In TSS, the processing time of the computer is divided into each user and switched in a short time.He gained ideas from TSS and thought that it would be efficient if the data was divided into finely divide the data and shared the line by multiple users.By the way, he is said to have used the communication term "packet" and "packet exchange" first.

However, it was thought that it was an unrealistic technology among experts at the time because it requires complicated processing for packets.So Arpanet was born as an experimental packet exchange network.ARPANET shows the usefulness of packet replacement and proved that it can be practical.

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