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Many Independent Networks • By late 1970s, many organizations began installing Local Area Networks because they: – Were inexpensive. – Were easy to install – Could operate them independently of a central administration. 3 The Proliferation of LANs • Advantages – An organization can: • budget funds • decide who has access • devise policies for use • Disadvantages – Independent groups can: • Encourage proliferation of different LAN technologies 4 Facts About LANs • Engineers have devised many LAN technologies • LAN performance determines cost. • LAN technology may only work with specific computers. 5 LANs Are Incompatible • Various LAN technologies are completely incompatible. – Connecting multiple LANs is not possible • Engineered to operate over limited distance • May be electrically incompatible • Encoding information may not make sense to another LAN 6 Wide Area Technologies Exist • WAN technology includes an additional special-purpose computer at each site that: –Connects to the transmission lines –Keeps communication independent of the computer 7 Few WANs, Many WANs • WANs cost much more than LANs. –Require more planning –Require more hardware • Only a few companies build their own WAN. 8 WANs And LANs Are Incompatible • Many Wide Area Networks and Local Area Networks exist. –Cannot connect a WAN to a LAN –Cannot interconnect the wires from two different networks 9 The Desirability Of A Single Network • Users should not have to: – Transfer data manually between one network and another. – Move from one computer to another to access different resources. • The best solution is for a computer to have access to all resources. 10 The Department Of Defense Had Multiple Networks • The Defense Department became interested in networks by the late 1960s. • ARPA realized that each network: – Connected a set of computers. – Formed an isolated island with no path between the islands. 11 Connecting Disconnected Machines • ARPA started with a few basic ideas. – Awarded grants to researchers in both industry and academia – Arranged for cooperation in solving problems • Discussed findings • Generated new ideas at regular meetings • Built a prototype to test their ideas 12 The Internet Emerges • ARPA funded research to investigate ways to solve the problem of incompatible networks. – Became known by the name Internet The Internet Emerges by Melissa Lee 13 The ARPANET Backbone • The ARPANET: –Served as a standard network to move data –Allowed researchers to evaluate new network software and applications. 14 Internet Software • Software makes it possible to interconnect networks. –Consists of many programs that interact in complex ways –Formed an integrated system –Resulted in a smooth, almost seamless design 15 The Name Is TCP/IP • Two pieces of Internet software stand out as important and innovative. – The Internet Protocol (IP) • Provides basic communication – Transmission Control Protocol (TCP) • Provides additional facilities 16 The Shock Of An Open System • ARPA made the research public. – Asked researchers to: • Document results in a report. • Document all experience installing and using the software. • Maintain an open system of compatible technology. 17 Open Systems Are Necessary • A large organization needs an open system because it: –Acquires computers from multiple vendors. –Does not restrict computers that connect to the network. 18 TCP/IP Documentation Is Online • Initially researchers planned to issue report in two steps: – Available for comment • Request for Comments (RFC) – Finalized version • Internet Engineering Note (IEN) • Eventually RFC reports became the official record. 19 The Military Adopts TCP/IP • By 1983, ARPA expanded the Internet to include all military sites connected to the ARPANET. – Marked a transition for the Internet – Changed the Internet from an experiment to a useful network 20 21 Glossary • ARPA • – Abbreviation for Advanced Research Projects Agency. Backbone Network – Used to refer to a central network to which many routers connect. 22 Glossary • Internet • – The collection of networks and routers that use the TCP/IP protocol suite and function as a single, large network. Open System – A non-proprietary technology or system: any vendor can use the specifications of an open system to build products and services. 23 Glossary • RFC • – Abbreviation for Request For Comments. TCP/IP – Literally, the name of protocols that specify how computers communicate on the Internet. 24 Glossary • TCP/IP Software • – The name of the software that implements the protocols. Wide Area Network (WAN) – Any network technology that can span long geographic distances. 25