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The following diagram shows the evolution of the Internet:



                                                During the Cold War, the US
                                               Department of Defense (DoD)
                                                recognized the need to build
                                                fault-tolerant networks that
                                                would not fail in the event of
                                                 a nuclear attack and could   The United States
                        It was in 1876 that Alexander   withstand a single point of   Department of Defense saw
                         Graham Bell proposed the   failure. Digital packet switching,   the need to link different   TCP/IP (Transmission Control
                         idea of communication via   which divides the message to   geographic research   Protocol/Internet Protocol)
                        telephone lines. This led to                      computers to build a   was created in 1970 for
                         the creation of the Public   be conveyed into little portions   network. As a result, in 1969,   communication between
                        Switched Telephone Network   called packets, was proposed by   the Advanced Research   multiple heterogeneous
                         (PSTN) in 1877. It ushered   Paul Baran, Donald Davies, and             networks. Along with
                        in new horizons by allowing   Len Kleinrock. Packet switching   Projects Agency (ARPA) of   many smaller networks,
                        people to communicate via   is based on link sharing, as   the Pentagon created a   the National Science
                         telephone lines. From that   opposed to circuit switching,   computer network named   Foundation (NSF) of the
                          time, communication    which reserves resources along   ARPANET. ARPANET made use   United States created NSFNET
                           was mainly through    a dedicated communication   of digital packet switching
                            telephone lines.           line.                technologies.       in 1984 for research and
                                                                                                  teaching purposes.





                 When ARPANET and NSFNET were linked together, the network’s growth exploded. The TCP/IP protocol (communication
                 rules) served as a glue to bring together many heterogeneous networks into a single network. Thus, the Internet was
                 born. The Internet is a large network (network of networks).


                                                                                                   #Subject Enrichment
                           Video Session


                     Scan the QR code or visit the following link to watch the video: Evolution of the Internet
                     https://www.youtube.com/watch?v=km9-XQZkOSE
                     Now answer the following questions:
                     1.  How many nodes were initially connected to ARPANET?
                         .....................................................................................................................................................................................
                     2.  Who invented the WWW?
                         .....................................................................................................................................................................................
                     3.  Who launched the first internet-enabled mobile phone?
                         .....................................................................................................................................................................................




                        Do You Know?


                        •  75 million servers control the Internet.
                        •  Over 550000 miles of underwater cable form the internet’s backbone.
                        •  The internet connects roughly one billion computer systems.
                        •  To answer a single Google search query, 1000 server computers are used in 0.2 seconds.









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