ComputerNetworkPrinciples(EnglishVersion)CourCATALOGUE目錄NetworkingPrinciplesOverviewNetworktopologyandprotocolsNetworkHardwareNetworkSoftwareNetworkArchitectureandDesign01NetworkingPrinciplesOverviewLocalAreaNetworks(LANs)Alocalareanetworkisanetworkthatcoversasmallgeographicalarea,suchasahome,office,orbuilding.LANsaretypicallyusedtoconnectcomputerswithinaconfinedspace.WideAreaNetworks(WANs)Awideareanetworkisanetworkthatcoversalargegeographicalarea,suchasacountryorcontinent.WANsaretypicallyusedtoconnectcomputersacrosslongdistances,oftenusingtelephonelinesorfiberopticcables.MetropolitanAreaNetworks(MANs)Ametropolitanareanetworkisanetworkthatcoversalargeurbanarea,typicallyacityormetropolitanregion.MANsareusedtoconnectcomputerswithinthecitylimitsoralargergeographicalarea.ClassificationofComputerNetworksTheImportanceofComputerNetworksEnhancedcommunication:Computernetworksallowpeopletocommunicateandshareinformationquicklyandefficiently,regardlessoftheirphysicallocation.Resourcesharing:Computernetworksenableuserstoshareresourcessuchasfiles,printers,andapplications,savingtimeandeffort.Collaboration:Computernetworksfacilitatecollaborationamongusers,allowingthemtoworktogetheronprojectsandtasksthatrequiremultiplepeople'sinput.Disasterrecovery:Computernetworksprovideanimportantbackupandrecoverymechanismincaseofnaturaldisastersorotheremergencies,allowingcriticalinformationtobepreservedandretrieved.02NetworktopologyandprotocolsAsinglecablethatrunsthelengthofthenetwork,connectingalldevices.BusTopologyStarTopologyRingTopologyMeshTopologyEachdeviceisconnecteddirectlytoacentralhub.Devicesareconnectedinaclosedloop,withdatatravelinginonedirection.Eachdevicehasaconnectiontoeveryotherdeviceinthenetwork.NetworkTopologyProtocolTCP(TransmissionControlProtocol)Ensuresreliable,ordereddeliveryofdata.UDP(UserDatagramProtocol)Providesasimple,connectionlessservicefordeliveryofsmallmessages.IP(InternetProtocol)Enablesdatatoberoutedacrossmultiplenetworks.HTTP(HypertextTransferProtocol)Usedforwebbrowsingandretrievinginformationfromwebservers.Layer4TransportLayer:Ensuresreliabledeliveryofdata,handlingsegmentation,reassembly,anderrorcontrol.Layer7ApplicationLayer:Handlesapplication-specifictasks,suchasemailandwebbrowsers.Layer6PresentationLayer:Ensuresdataisinaformatthatcanbeinterpretedatthereceivingend.Layer5SessionLayer:Managestheestablishmentandterminationofcommunicationsessions.TheOSIModel03NetworkHardwareNetworkInterfaceCardsNetworkInterfaceCards(NICs):Thesearethehardwarecomponentsthatareresponsibleforconnectingacomputertoanetwork.Theyprovidethephysicallayerinterfacebetweenthecomputerandthenetworkcable.TypesofNICs:TherearedifferenttypesofNICsavailable,suchasPCI,PCIe,USB,andThunderbolt,eachdesignedfordifferenttypesofcomputersandnetworkrequirements.Functionality:NICsareresponsibleforconvertingdatafromthecomputerintoaformatthatcanbetransmittedoverthenetworkcableandviceversa.Theyalsohandlenetworktrafficandprovideconnectionmanagementfunctionalities.Performance:TheperformanceofaNICdependsonvariousfactors,includingitsspeed(measuredinMbps),driversupport,andqualityofcomponentsusedinitsmanufacture.RoutersandSwitchesRouters:Routersaredevicesthatconnectmultiplenetworksandforwarddatapacketsbetweendifferentnetworks.Theyhandleroutingdecisionsbasedondestinationaddressesandensurethatdatareachesitsintendeddestination.Switches:Switchesaredevicesthatconnectcomputersonanetworkandforwarddatapacketsbetweenthem.TheyoperateatthedatalinklayeroftheOSImodelandcanfilterandcontroltrafficbasedonMACaddresses.Functionality:Routersandswitcheshavedifferentfunctionalitiesbutbothareessentialformaintainingnetworkconnectivityandperformance.Routersroutedatabetweendifferentnetworks,whileswitchesforwarddatabetweencomputerswithinanetwork.Differences:Routersandswitchesdifferintheirfunctionalityandusecases.Routersroutedatabetweendifferentnetworks,whileswitchesforwarddatawithinasinglenetwork.Routershavetheabilitytohandlemorecomplexroutingprotocolsandcanconnectdifferenttypesofnetworks,whereasswitchesaredesignedtoconnectcomputerswithinasinglenetworksegment.WiringandCablingWiring:Wiringreferstothephysicalcablesandconnectionsthatareusedtoestablishanetworkconnectionbetweendevices.Thetypeofwiringuseddependsonthenetworktechnologybeingimplemented.Cabling:Cablingreferstothecablesthatareusedtotransmitdatabetweendevicesonanetwork.Therearedifferenttypesofcabling,suchastwisted-pairandcoaxialcabling,eachsuitablefordifferenttypesofnetworksanddistances.TypesofCabling:CommontypesofcablingincludeCat5,Cat6,andCat7cables,whicharetwisted-paircablesusedforEthernetnetworking.Othertypesofcablingincludecoaxialcabling(suchasRG-6)andfiberopticcabling.PerformanceCharacteristics:Theperformancecharacteristicsofwiringandcablingarecrucialfornetworkconnectivityandspeed.Differenttypesofcablinghavedifferentmaximumdistancesoverwhichtheycantransmitdata,aswellasmaximumdatatransferrates.04NetworkSoftwareOperatingSystemsandNetworkSoftwareOperatingSystems:Anoperatingsystemisapieceofsoftwarethatmanagesthecomputer'sresourcesandprovidesaninterfacebetweenthecomputerhardwareandtheuser.Itisresponsibleforallocatingmemory,processingpower,andotherresourcestodifferentprogramsandprocessesrunningonthecomputer.SomepopularoperatingsystemsincludeWindows,macOS,andLinux.NetworkSoftware:Networksoftwareisasetofprogramsthatenablecomputerstocommunicateandinteractwitheachotheroveranetwork.Itincludesprotocols,routers,switches,andothercomponentsthatfacilitatedatatransmissionandnetworkmanagement.SomecommonnetworkprotocolsincludeTCP/IPandHTTP.NetworkUtilitiesNetworkutilitiesareprogramsthatprovidespecificfunctionalitiestohelpmanageandtroubleshootnetworkissues.Theseutilitiescanrangefromsimpletoolsforcheckingnetworkconnectivitytomoreadvancedtoolsfordiagnosingnetworkproblemsandoptimizingnetworkperformance.Someexamplesincludeping,traceroute,andWireshark.NetworkApplicationsNetworkapplicationsaresoftwareprogramsthataredesignedtoperformspecifictasksorprovidespecificservicesoveranetwork.Theseapplicationscanrangefromwebbrowsers,emailclients,filetransfertools,tomorespecializedapplicationslikeVoIP(VoiceoverIP)softwareorvideoconferencingsoftware.NetworkUtilitiesandApplicationsFirewallsaresecuritydevicesthatfilterincomingandoutgoingtrafficbasedonpredefinedsecurityrules.Theycanblockunauthorizedaccesstothenetworkandprotectagainstvarioustypesofnetworkattacks,suchasviruses,worms,andmalware.FirewallsEncryptionisaprocessofconvertingplaintextdataintociphertextusingasecretkeyoralgorithm.Itisusedtoprotectsensitiveinformationtransmittedoveranetworkfrombeinginterceptedortamperedwith.SomecommonencryptionprotocolsincludeSSL/TLSandWEP/WPA/WPA2.EncryptionNetworkSecurity05NetworkArchitectureandDesignClient-ServerArchitecture01Anetworkarchitecturewhereclientsrequestservicesfromservers.Clientsandserverscommunicateoveranetworktoshareresourcesandinformation.Peer-to-PeerArchitecture02Anetworkarchitecturewhereeachnodehasthesamecapabilitiesandresponsibilities.Nodescommunicatedirectlywitheachotherwithouttheneedforcentralizedservers.HierarchicalArchitecture03Anetworkarchitecturewherenodesareorganizedintolayersbasedontheircapabilitiesandresponsibilities.Eachlayerprovidesservicestothelayeraboveit.NetworkArchitectureTopologyDesignThephysicalandlogicallayoutofthenetworknodesandlinks.Topologydesignconsiderationsincludenetworkscalability,faulttolerance,andperformance.ProtocolDesignTherulesandproceduresthatgovernhownetworknodescommunicatewitheachother.Protocoldesignconsiderationsincludedatatransmission,e