54Computer Network

INTRODUCTIONTOCOMPUTERNETWORKSSantoshKumarSahuMasterinComputerApplicationSoftwareSchool,NanchangUniversityJiangxi,China(QQ:860397288,Email:[e-mail])WhatisComputer?•Computerisaelectronicdevice,thatcanaccept,store,processanddisplayinformationofitsuser.•Nowadayswhereeverwecangowecanseethecomputers,nolifewithoutcomputers.Everyfieldweusecomputers,becausenowitisusedforcomputingpurpose,itisusedfordifferentpurpose.WhatisNetwork?•Anetworkisacollectionofterminals,computers,servers,andcomponentswhichallowsfortheeasyflowofdataanduseofresourcesbetweenoneanother.ComputerNetworksComputernetworkconnectstwoormoreautonomouscomputers.Thecomputerscanbegeographicallylocatedanywhere.IntroductiontoComputerNetworksComputerNetworksAcomputernetworkisagroupofcomputersandotherrelateddevicesinterconnectedbycommunicationschannelsthatfacilitatecommunicationsamongusersandallowsuserstoshareresourcesIntroductiontoComputerNetworkscommunicationschannelsCopperWires.FiberopticsmicrowavesinfraredSatellitesRoutershubsetc…IntroductiontoComputerNetworksApplicationsofNetworksIntroductiontoComputerNetworksResourceSharingHardware(computingresources,disks,printers)Software(applicationsoftware)InformationSharingEasyaccessibilityfromanywhere(files,databases)SearchCapability()CommunicationEmailMessagebroadcastRemotecomputingUsesofComputerNetwork1.1.1BusinessApplicationsResourcesharing-makeallprograms,data,andequipmentavailabletoanyoneonthenetworkwithoutregardtothephysicallocationHighreliability-Incaseofoneresourcefailure,theotherscouldbeused.Savingmoney:Scalability:-TheabilitytoincreasesystemperformancegraduallybyaddingmoreprocessorsPowerfulcommunicationmedium-Networksmakecooperationamongfar-flunggroupsofpeopleeasywhereitpreviouslyhadbeenimpossible.IntroductiontoComputerNetworksUsesofComputerNetwork1.1.2.NetworksforpeopleAccesstoremoteinformation:Person-to-personcommunication:InteractiveentertainmentElectroniccommerce.IntroductiontoComputerNetworksAccesstoremoteinformation:•Homereservationsforairplanes,trains,hotels,restaurants,theaters,andsoon,anywhereintheworldwithinstantconfirmation.•Homebankingandshopping.•On-lineandpersonalizedelectronicnewspapers,journals,andlibraries.•Accessto(WorldWideWeb)whichcontainsinformationaboutmanytopics-toomanytomention!IntroductiontoComputerNetworksPerson-to-personcommunication:•Electronicmailsoremailsforeveryone.•Videoconferencingandvirtualmeetingenvironments,allowremoteuserstocommunicatewithnodelay,possiblyseeingandhearingeachothersaswell.Electroniccommerce1.1.3MobileUsers•Mobilecomputers,suchasnotebookcomputersandpersonaldigitalassistants(PDAs),IPAD,WEPADareoneofthefastestgrowingsegmentsofthecomputerindustry.1.1.4SocialIssues•Thewidespreadintroductionofnetworkingwillintroducenewsocial,ethical,politicalproblems:•Shouldsubjectsberegulatedifnewsgroupsaresetupontopics,suchaspolitics,religion,fashion,cultureorsportsDistributedSystems•Collectionofautonomouscomputers,connectedthroughanetwork,whichenablescomputerstocoordinatetheiractivitiesandtosharetheresourcesofthesystem,sothatusersrecognizethesystemasasingle,integratedcomputingfacility.•Ex––Internet-WebpagesComputerNetworksVs.DistributedSystems•ComputerNetworks:•Acomputernetworkisaninterconnectedcollectionofautonomouscomputersabletoexchangeinformation.•Acomputernetworkusuallyrequireuserstologinontoonemachine,submitjobsremotely,movefiles/dataaroundthenetwork.ComputerNetworksVs.DistributedSystems•DistributedSystems:•Theexistenceofmultipleautonomouscomputersinacomputernetworkistransparent(open)totheuser.•Theoperatingsystemautomaticallyallocatesjobstoprocessors,movesfilesamongvariouscomputerswithoutuserinterference.ClientandServerSystem•ComputerusedbythecommonuseriscalledClient•ServerispowerfulcomputerstoreandmaintainthecentralizeddataandoperatedbytheAdministrators.ClientandServerSystem•Theclient-servermodelinvolvesrequestsandreplies.Peer-to-Peer•person-to-personcommunicationoftengoesbythenameofpeer-to-peercommunication•Inapeer-to-peersystemtherearenofixedclientsandservers.WAP•WAP(WirelessApplicationProtocol)isaspecificationforasetofcommunicationprotocolstostandardizethewaythatwirelessdevices,suchascellulartelephonesandradiotransceivers,canbeusedforInternetaccess,includinge-mail,theWorldWideWeb,newsgroupsetc…1.2NetworkHardware•Thiscanbealonglist.SomeoftheHardwaredevicesusedinNetworkareRouters,Switches,Modems,Hubs,LANCardsetc.•Herewewilldiscussaboutthetransmission(Spreading)technologiesTransmissiontechnologies•1.Broadcastlinks.–Broadcastnetworkshaveasinglecommunicationchannelthatissharedbyallthemachinesonthenetwork.–Shortmessages,calledpacketsincertaincontexts,sentbyanymachinearereceivedbyalltheothers–Somebroadcastsystemsalsosupporttransmissiontoasubsetofthemachines,somethingknownasmulticastingTransmissiontechnologies•2.Point-to-pointlinks.•point-to-pointnetworksconsistofmanyconnectionsbetweenindividualpairsofmachines.•Point-to-pointtransmissionwithonesenderandonereceiverissometimescalledunicastingClassificationofNetworks•PAN–PersonalAreaNetworks•LAN–Loca