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Initially, the scope of ARPANET was restricted to military and research.  Subsequently, its use extended to education
        by supporting various educational institutes. In the 1970s, other networks such as SatNet (Satellite Network), Packet
        Radio, and Ethernet LAN came into being. Different networks deployed different technologies. So, a unifying mechanism
        was required to enable communication between the networks with heterogeneous technologies.  Towards this end,
        Cerf and Kahn developed TCP/IP (Transmission Control Protocol/Internet Protocol) in 1970. TCP/IP became the de facto
        standard for communication during the early eighties. It facilitated interconnectivity amongst heterogeneous networks.
        In late 1984, National Science Foundation (NSF) created NSFNET — a network with six supercomputers that aimed to
        promote advanced research and education. Several regional networks of  universities could access these supercomputers
        via a computer network. Subsequently, in the 1990s, several other countries and regions developed their networks for
        scientific and commercial purposes. When ARPANET and NSFNET were interconnected, the network growth increased
        tremendously. This vast network formed the Internet (network of networks), and its growth connected the whole world.
        In the mid-1990s, the number of hosts connected through the Internet grew exponentially.  Several organisations in
        government and private sectors (collectively called Internet Service Providers (ISPs)) joined hands to provide Internet
        connectivity. The Internet made it possible to exchange information and communicate with remote hosts. The Internet
        provides several services such as
        •  Email:  Sending and receiving electronic messages.
        •  File Transfer: Files can be copied/transferred from one system to another.
        •  Newsgroup: A newsgroup is a discussion forum where users of related interest can post information and reply to
           others’ posts.
        •  Remote login: Remote login enables users on one system to log into a remote system and use hardware and
           software available at the remote computer.
        •  Chat: Chat provides real-time communication between two or more users. It allows the connected users to exchange
           messages in a chat window. Examples of chat applications include WhatsApp, Facebook messenger,  and Telegram.

        •  Video Conferencing: Video Conferencing allows multiple users to exchange video and voice messages in real-time.
           Examples: Video calls using applications like Facebook and WhatsApp, or more sophisticated tools like  Google
           Meet, Zoom  Meetings, Cisco Webex.
        •  Cloud  Computing:  Cloud  Computing  enables  storage  and  computing  services  over  the  Internet.  For  example,
           Google Cloud Platform (GCP), Amazon Web Services (AWS), and Microsoft Azure enable collaborative computing
           environments.
        •  Interspace: Interspace is a client/server software tool that allows users to connect online in dynamic 3D worlds
           using real-time audio, video, and text chat.


               Interspace is a client/server software program that allows multiple users to communicate.





                 1.     Rimit and Azaad are connected with each other through video and voice in real time. Which internet
                     service are they using?
                 2.     Abha has created a document in Google Drive and shared it with her friends. Is she using a Cloud
                     Computing service?



        6.3 Network Topologies

        We already know that a network connects computers and devices (collectively called nodes). The arrangement of
        nodes in a network is called topology. It describes the placement of various network devices and physical connections
        between them. We will discuss various topologies of networks in this section.


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