ch14 连网与网络互连

14.1CHAPTER14:CHAPTER14:NETWORKINGANDINTERNETWORKINGNETWORKINGANDINTERNETWORKING„ObjectiveszzTCP/IPIPz/zzshellzfinger,ftp,ifconfig,nslookup,ping,rcp,rlogin,rsh,ruptime,rusers,rwho,talk,telnet,traceroute114.2IntroductionIntroduction„Inthelate1960s,AdvancedResearchProjectsAgency(ARPA)startedfundingnetworkingresearch„Inthelate1970s,awideareanetwork,ARPANETwasdeveloped„Theearlyinternet,usingtheTCP/IPprotocolsuitebecameoperationalin1982„Theearlyinternetconnectedafewacademic,researchandU.Smilitaryorganizations214.3Introduction(contIntroduction(cont))„In1983only562siteswereconnectedtotheInternet„In1991,thefirstwebbrowser,Mosaicwasdeveloped„By1996,thenumberofcomputersconnectedtotheInternethasreachedto9.5million„Today,almost300million3?,30computers,and1millionnetworksareconnectedtotheInternet„MostnetworkingtechnologiesandprotocolswereinitiallyimplementedonLinuxorUnixplatforms314.4ComputerNetworksandComputerNetworksandInternetworksInternetworks„Iftwoormorehardwareresources(computers,printers,etc)areconnectedtoeachother,theyformacomputernetwork„Eachhardwareresourceonacomputernetworkiscalledahost414.5ComputerNetworksandComputerNetworksandInternetworks(contInternetworks(cont))„Computernetworkcategoriesaccordingtothedistancebetweenhosts:zLAN(LocalAreaNetworks):Connecthostsinaroom,inabuildingorinacampuszMAN(MetropolitanAreaNetworks):ConnecthostswithinacityzWAN(WideAreaNetworks):Connecthostsacrosscities,countries,continents514.6ComputerNetworksandComputerNetworksandInternetworks(contInternetworks(cont))„„(router)(gateway)Internet614.7„„„„bit714.8NetworkModelsNetworkModels„z(ISOOSI)zTCP/IPUsedintheInternet14.914.10TCP/IPTCP/IPTCP/IPProtocolTCP/IPProtocol„Aprotocolis:zThesetofrulesthatboththesenderandthereceiveragreetouseduringdatacommunication„Bothpartiesmustusethesameprotocolsoftwareinordertocommunicate„Eachprotocolperformsacertainpartofthenetworkingprocess„Severalprotocolsareinvolvedineverycomputernetwork,andtheyareknownasprotocolsuites1014.11TCP/IPProtocolTCP/IPProtocol„TheTCP/IPprotocolsuiteTCP/IPisthemostwidelyusedone„ThepublicInternetusestheTCP/IPprotocolsuite„TheTCP/IPprotocolsuiteandtherelationshipsbetweenindividualprotocols,canbeillustratedinalayereddiagram„ThislayereddiagramiscalledtheTCP/IPLayeredModel1114.12TCP/IPProtocolTCP/IPProtocol14.3TCP/IP1214.13TCP/IPProtocolTCP/IPProtocol„AtthetopoftheTCP/IPlayeredmodelistheapplicationlayerthatcontainsapplicationprogramsandutilitiesthatprovidesvariousinternetservicestotheuser:ze-mail,zwebbrowsing,zfiletransfer,zremotelogin,etc1314.14TCP/IPProtocolTCP/IPProtocol„ThetransportlayerisresponsibleforthedeliveryoftheapplicationdatatotheotherpartyzTCPprotocoloffersaconnectionoriented,completelyreliableandin-sequencedelivery(mostinternetapplicationsusethisprotocolattransportlayer.E.g.Telnet,ftp)zUDPprotocoloffersaconnectionless,fast,andunreliabledelivery1414.15TCP/IPProtocolTCP/IPProtocol„Onamultiprocesssystem,usuallymorethanoneprocess(application)useTCPorUDPprotocolsatthesametime(Forex:Webbrowsingandtelnet)„Protocolsusea16-bitnumber(0-65535)calledportnumbers,toidentifywhichdatapacketgoestowhichapplication„Portnumbers0-1024arecalledwell-knownportnumbersandaredistributedbyInternetAssignedNumbersAuthority(IANA)1514.16TCP/IPProtocolTCP/IPProtocol„Somewell-knownTCPportnumbers:zFtp:21zTelnet:22zWebserver:801614.17TCP/IPProtocolTCP/IPProtocol„Thenetworklayerisresponsiblefortheroutingofapplicationsdatatothedestination„Internetprotocol(IP)isusedtoperformthistask„IPprotocolusesanaddressingschemecalledIPAddressingzIPv4uses32-bitnumberszIpv6uses128-bitnumbers„EveryhostontheInternetmusthaveatleastoneIPaddress1714.18TCP/IPProtocolTCP/IPProtocol„AnIPaddressisa32-bitbinarynumber,usuallywrittenindotteddecimalnotationz11000000011001100000101000010101iswrittenasz192.102.10.21indotteddecimalnotation„ThenumberofIPaddressesassignedtoasinglehostcorrespondstothenumberofnetworkconnectionsthathosthas1814.19TCP/IPProtocolTCP/IPProtocol„EachIPv4addressisdividedintothreeparts:zAddressclasszThenetworkid(prefix)(mustbeuniquewithintheInternet)zThehostid(suffix)inthatnetwork(mustbeuniquewithintheLAN)„IPABCDEABCIPDE1914.20TCP/IPProtocolTCP/IPProtocol2014.21TCP/IPProtocolTCP/IPProtocol2114.22TCP/IPProtocolTCP/IPProtocol„Thedivisionpointofthenetworkidandhostidisdeterminedbythesubnetmask(orAddressmask)„Subnetmaskisanother32-bitbinarynumbersimilartotheIPaddress2214.23TCP/IPProtocolTCP/IPProtocol„IPaddress-Subnetmaskexample:zIPAddress:11000000011001100000101000010101(or192.102.10.21indotteddecimalnotation)zNetmask:11111111111111111111111100000000(or255.255.255.0indotteddecimalnotation)zThenetworknumberis:192.102.10zThehostnumberis:212314.24TCP/IPProtocolTCP/IPProtocol14.5Net1ANet3BNet2Net4C2414.25TCP/IPProtocolTCP/IPProtocol„IP127.0.0.0(127.*.*.**0255)Internet„25514.26TCP/IPProtocolTCP/IPProtocol„TheDomainNameSystem(DNS)zAlthoughInternetsoftwareusesIPaddresses,peopleprefertousesymbolicnameszThetranslationfromsymbolicnamestoIPaddressesisperformedbydomainnamesystem(DNS)zOrganizationsusededicatednameservers,thatmapdoma