May 28, 2024

ARPANET to Internet


ARPANET intially consisted of a number of diverse hosts. However, the subnet of IMPs were identical computers, running the same software. BBN was able to monotor and control all the IMPs. The transition of ARPANET into the Internet was brought about by the introduction of two protocols.

  • Internet Protocol (IP)
  • Transport Control Protocol (TCP)

Other packet-switched systems came into operation around the same time as the advent of ARPANET:

  • Britain - NPL system
  • France - Cyclades network
  • Hawaii - ALOHA packet-radio network
  • SATNET - satellite network

Basic problem - "internetworking" proved impossible due to the incompatibility of the systems, even though they were all based on packet-switching.

The solution was achieved by the introduction of:

  1. Gateways - computers were to act as links between networks.
  2. Hosts were to be made responsible for end-to-end transmission of packets, together with error correction and retransmission if necessary.
  3. Protocols were written to implement 1 and 2.

Together, these two protocols are referred to as TCP/IP and provided for the linking of any network to the rest of the evolving Internet. This linkage was made via the gateway, which utilised the protocols. TCP/IP promoted the organic growth of the Internet (read this essay). All OSs, e.g. Windows, MacOS, are bundled with TCP/IP.


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