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1、附录A英文阅读材料本阅读材料引自BehrouzA.Forouzan所著DATACOMMUNICATIONSANDNETWORKINGSECONDEDITION,McGraw-HillCompanies,Inc.(清华大学影印版2001.4)。在此，特对作者表达谢意！CHAPTER24TCP/IPProtocolSuite:Part1TheTransmissionControlProtocol/InternetworkingProtocol(TCP/IP)isasetofprotocols,oraprotocolsuite,thatdefineshowalltra
2、nsmissionsareexchangedacrosstheInternet.Namedafteritstwomostpopularprotocols,TCP/IPhasbeeninactiveuseformanyyearsandhasdemonstrateditseffectivenessonaworldwidescale.24.1OVERVIEWOFTCP/IPIn1969,aprojectwasfundedbytheAdvancedResearchProjectAgency(ARPA),anarmoftheU.S.DepartmentofDefense.
3、ARPAestablishedapacket-switchingnetworkofcomputerslinkedbypoint-to-pointleasedlinescalledAdvancedResearchProjectAgencyNetwork(ARPANET)thatprovidedabasisforearlyresearchintonetworking.TheconventionsdevelopedbyARPAtospecifyhowindividualcomputerscouldcommunicateacrossthatnetworkbecameTC
4、P/IP.Asnetworkingpossibilitiesgrewtoincludeothertypesoflinksanddevices,ARPAadaptedTCP/IPtothedemandsofthenewtechnology.AsinvolvementinTCP/IPgrew,thescopeofARPANETexpandeduntilitbecamethebackboneofaninternetworktodayreferredtoastheInternet.TCP/IPandtheInternetTCP/IPandtheconceptofinte
5、rnetworkingdevelopedtogether,eachshapingthegrowthoftheother.Beforemovingmoredeeplyintotheprotocols,however,weneedtounderstandhowTCP/IPrelatestothephysicalentityofanyInternetitserves.AninternetunderTCP/IPoperateslikeasinglenetworkconnectingmanycomputersofanysizeandtype.Internally,anin
6、ternet(or,morespecifically,theInternet)isaninterconnectionofindependentphysicalnetworks(suchasLANs)linkedtogetherbyinternetworkingdevices.Figure24.1showsthetopologyofapossibleInternet.Inthisexample,thelettersA,B,C,andsoonrepresenthosts.AhostinTCP/IPisacomputer.Thesolidcirclesinthefig
7、ure,numbered1,2,3,andsoon,areroutersorgateways.Thelargerovalscontainingromannumerals(I,II,III,etc.)representseparatephysicalnetworks.Figure24.1AninternetaccordingtoTCP/IPToTCP/IP,thesameinternetappearsquitedifferently(seeagainFigure24,1).TCP/IPconsidersallinterconnectedphysicalnetwor
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