What is the INTERNET?• The Internet is the system which connectscomputer networks. Internet links millions ofcomputers all over the world. It allows yourcomputer to get information stored on othercomputers far away. Computers connect tothe Internet through telephone and cablesystems.• The largest network of networks in theworld.• Uses TCP/IP protocols and packet switching• Runs on any communications substrate.
• The Internet grew out of an experiment in the 1960s by theU.S. Department of Defense. The DoD wanted to create acomputer network that would continue to function in theevent of a disaster, such as a nuclear war. If part of thenetwork was damaged or destroyed, the rest of the systemstill had to work. That network was ARPANET, (AdvancedResearch Projects Agency Network) which linked U.S.scientific and academic researchers. It was the forerunnerof todays Internet.• 1968 - DARPA (Defense Advanced Research Projects Agency)contracts with BBN (Bolt, Beranek & Newman) to createARPAnet• 1974 - TCP specification by Vint CerfWhere did the Internet come from?
• 1984 – On January 1, the Internet with its 1000 hostsconverts en masse to using TCP/IP for its messaging• 1984Domain Name Server (DNS) introduced and number ofhost is 1,000 1986 NSFNET created a high speed backbone(56Kbps) to interconnect supercomputer centers 1987 Number of hosts breaks 10,000 1992 WWW released by CERN (a physics researchinstitute in Switzerland)Number of hosts breaks1,000,000 1995*.com sites exceed *.edu sites 1996 Electronic commerce gets going seriously
• The creation of the Internet solved the following challenges:– Basically inventing digital networking as we know it– Survivability of an infrastructure to send / receive high-speed electronic messages– Reliability of computer messagingCreation of the Internet
1977: 111 hosts on Internet 1981: 213 hosts 1983: 562 hosts 1984: 1,000 hosts 1986: 5,000 hosts 1987: 10,000 hosts 1989: 100,000 hosts 1992: 1,000,000 hosts 2001: 150 – 175 million hosts 2002: over 200 million hosts By 2010, about 80% of the planet will be on the InternetInternet Growth Trends
• Transport control protocol (TCP)– A protocol that operates at the transport layer and isused in combination with IP by most Internetapplications• Backbone– An Internet high-speed, long distance communicationslinks (like a bus; wire that connects nodes)• Uniform resource locator (URL)– An assigned address on the Internet for each computer– E.g., http://www.yorku.ca/How the internet works
Access to the Internet• LAN servers• Local servers can provide access to the Internetthrough normal connections (e.g., Ethernet)• Serial line internet protocol (SLIP) andPoint-to-point protocol (PPP)• Communications protocol software that transmitspackets over telephone lines, allowing dial-up accessto the Internet• Connection via an on-line service• Examples are America Online and Microsoft Network.These services usually require sign-up procedures
• The Web physically consists ofyour personal computer, webbrowser software, aconnection to an Internetservice provider, computerscalled servers that host digitaldata, and routers and switchesto direct the flow ofinformation.Net structure
• A web browser is the softwareprogram you use to access theWorld Wide Web, the graphicalportion of the Internet. Thefirst browser, called NCSAMosaic, was developed at theNational Center forSupercomputing Applications inthe early 1990s. The easy-to-use point-and-click interfacehelped popularize the Web.Microsoft Internet Explorer andNetscape Navigator are the twomost popular ones.Web Browser
• World Wide Web is a network of electronic files stored onmillions of computers all around the world. Hypertext linksthese resources together. Uniform Resource Locators orURLs are the addresses used to locate the files. Every URL isunique and identifies one specific file.• example:http://www.mu.ac.inThe home page of Mysore University.Web Addresses
• Every computer that hosts data on the Internet has a uniquenumerical address. For example, the numerical address forthe White House is 188.8.131.52. But since few peoplewant to remember long strings of numbers, the DomainName System (DNS) was invented. DNS, a critical part of theInternets technical infrastructure, correlates a numericaladdress to a word. To access the White House website, youcould type its number into the address box of your webbrowser. But most people prefer to use"www.whitehouse.gov." In this case, the domain name iswhitehouse.gov.Domain Names
Domain AffiliationsDomain AffiliationsArts cultural and entertainment activitiesCom business organizationsEdu educational sitesfirm businesses and firmsgov government sitesinfo information service providersmil military sitesnom individualsnet networking organizationsorg organizationsrec recreational activitiesstore businesses offering goods for purchaseweb entities related to World Wide Web activitiesnet networking organizations