How did the Internet evolve?

The Internet was not an overnight development, it has evolved over thirty years and can be traced back to the first computer networking projects, the key developments & personalities of which will be explained in this section.

Following the launch of Sputnik (the first artificial earth satellite) by the USSR in 1957, the US Department of Defense formed the Advanced Projects Research Agency (ARPA) to establish a lead in world technology for the USA.

The first head of this organisation was J.C.R. Licklider, who wrote a series of memos in 1962 discussing his ideas of a "Galactic Network", a global set of computers that were interconnected and allowed users to access data and programs from any site. He promoted his networking theory to his successors at ARPA, Ivan Sutherland, Bob Taylor and Lawrence G Roberts.

In 1965, Lawrence Roberts directly connected a TX-2 computer at MIT in Massachusetts to a Q-32 computer in California via a dedicated phone line. This experiment was the first-ever Wide Area Network (WAN), (the first Local Area Network (LAN) was developed some years later by Bob Metcalfe at Xerox PARC, using the Ethernet protocol, which is probably the dominant network technology on today's Internet).

The experiment proved that time-sharing computers could network but it also proved that the circuit switching was not adequate and he approached ARPA to develop the computer network concept further. The result was his plan for the ARPANET, a number of individual computers connected by leased lines using packet switching. Roberts had been convinced on the theory of using packet switching by Leonard Kleinrock, who wrote the first paper on packet-switching theory in 1961, although three independent bodies worked on this concept, the National Physical Laboratory (NPL), RAND and MIT.

The first four nodes of ARPANET were at UCLA, Stanford Research Institute, UC Santa Barbara and University of Utah and these formed the initial ARPANET in 1969. The Network Working Group, headed by Steve Crocker, finished the initial ARPANET Host-to-Host protocol in 1970 which was called the Network Control Protocol (NCP). The implementation of this protocol enabled the network users to develop applications.

Bob Kahn, who had been working at Bolt Beranek & Newman (BBN), the company which had built the Interface Message Processors (IMPs) of the ARPANET, posed the problem of how computers could interwork without any knowledge of the characteristics of the underlying networks as there were more than one packet switched network. Bob Kahn employed the skills of Vint Cerf (previously involved in the design of NCP and the measurement of ARPANET) to establish a solution to getting these to "internetwork". They concluded that the following key features were needed:

• Using computers as gateways or routers between different networks
• Making hosts responsible for end-to-end transmission of packets together with error correction and retransmission if necessary
• Devising the protocols necessary to make the first two points happen

In 1974 Bob Kahn and Vint Cerf published "A Protocol for Packet Network Interconnection" which specified the Transmission Control Protocol (TCP). This new protocol, TCP, was eventually split into Transmission Control Protocol/Internet Protocol (TCP/IP) to make it even more efficient. In the early 1980s, TCP/IP was established as the protocols on the ARPANET, replacing the NCP.

Through the 1980's ARPANET was revised, and new networks were established including NSFNET, but TCP/IP was essential to them all. More and more networks have interconnected to form the Internet. Vint Cerf has stated in an online interview:

"Today, there are an unknown number of networks interconnected to form the Internet - certainly in excess of 200,000 around the world and likely more than that. There are at least 60 million computers on the Internet and possibly as many as 200 Million."

Source:
http://www.wcom.com/about_the_company/cerfs_up/

As the Internet and its capabilities has developed, more protocols have been added in a layered approach in addition to TCP/IP, such as the Domain Name System (DNS), the email protocols (POP3, IMAP, and SMTP) and the World Wide Web protocols (HTTP, HTML, and XML).

One of the keys to the rapid growth of the Internet has been the availability of basic documents and specifications of the protocols. These were available as Requests for Comments (RFCs). Jon Postel acted as the RFC Editor; in addition to his role as director of the Internet Assigned Numbers Authority, a non-profit body that administers the required protocol number assignments.