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1、Module7InternetAndInternetProtocolSuiteVersion1ECE,IITKharagpurLesson21InternetandIPv4Version1ECE,IITKharagpurLESSONOBJECTIVEGeneralThelessonwilldiscussapopularnetworklayerprotocol,i.e.theInternetProtocolSpecificThefocusareasofthislessonare:1.DefinitionofIPv4.2.StructureofIPv4header.3.Id
2、eaofVoIP.4.Variousclassesofserviceandtypesofnetworks.7.1.1INTRODUCTION:AttheX.25leveleachfundamentalentityisknownasapacket.InIPterminologywecallitasadatagram.Datagramwillhaveasourceanddestinationaddress.ThisaddressisknownasIPaddress.AlldevicesconnectedtotheinternetworkhaveanIPaddress.The
3、IPdatagramformatisasshowninthediagrambelow7.1.2IPV4IPv4Header0841631VersionHeaderTypeofServiceTotalLengthLengthIdentifierFlagFragmentOffsetTimetoliveProtocolHeaderCheckSumSourceAddressDestinationAddressOptions+PaddingUserDataVersion1ECE,IITKharagpurThevariousfieldsintheheadermaybeexplain
4、edasfollowsVersion:ThisfieldspecifiestheIPversionbeingusedIHLInternetHeaderLengthspecifiesthetotallengthoftheheaderin32-bitwords.Theminimumvalueis5.TypeofserviceItspecifiesthetypeofservicebeingprovided.TheparametersareParameterLevel1Precedence82Reliability23Delay24Throughput2TotallengthI
5、tspecifiesthetotallength(includingtheheaderandthedata)IdentifierItisused,alongwiththesourceanddestinationaddress,touniquelyidentifythedataunitFlagTheFlagfieldhas3bits,twoareforMoreandDon’trdfragmentindicator,the3isnotusedcurrently.FragmentoffsetIndicateswhereintheoriginaldatagramthisfrag
6、mentexistsTime-to-liveSpecifies,innumberofhops,howlongadatagramisallowedtoremaininthenetworkProtocolSpecifiestheupperlevelprotocolusedinthedestination.Headerchecksum:One’scomplementofmodulo-16additionofall16bitwordsintheheader.Sourceaddress32bitsDestinationAddress32bitsOptionsandDependin
7、gonISPsomeoptionsmaybeavailable.paddingPaddingisusedtoensurethedatagramheaderisamultipleof32bits.ThoughTCPandIPweredevelopedtogetherbyDODUSAtheyarenotreallydependent,theprotocolfieldinIPheaderspecifiesthetransportprotocolbeingused.Version1ECE,IITKharagpurISVOIPREALLYINEXP
