Fragmentation Offset - Internet Core Protocols - O'Reilly Media

The Fragmentation Offset field is used by the final destination system to figure out which fragment goes where in the reassembly process. Since there are no ... Skiptomaincontent InternetCoreProtocols:TheDefinitiveGuidebyEricHall GetfullaccesstoInternetCoreProtocols:TheDefinitiveGuideand60K+othertitles,withfree10-daytrialofO'Reilly. There'salsoliveonlineevents,interactivecontent,certificationprepmaterials,andmore. Startyourfreetrial NameFragmentationOffsetSynopsisIndicatesthestartingbyte positionoftheoriginalIPdatagram’sdatathatthisfragmentprovides,in 8-bytemultiples.SizeThirteenbits.NotesThefirstfragment’sFragmentationOffsetwillalways besetto0,indicatingthatthefragmentcontainsthefirst byteoftheoriginaldatagram’sdata.TheFragmentationOffsetfieldisusedbythefinal destinationsystemtofigureoutwhichfragmentgoeswhere inthereassemblyprocess.Sincetherearenofields thatprovidea“fragmentsequencenumber,”thedestination systemmustusethisfieldinconjunctionwiththeTotal PacketLengthfieldandtheMoreFragmentsflag.Forexample,let’sassumethatanIPdatagram’sdata hasbeensplitintotwo64-bytefragments.Thefirst fragment’sIPheaderwillshowaFragmentationOffsetof0, indicatingthatitcontainsthefirstfewbytesofthe originalIPdatagram’sdata.Aftersubtractingthevalueof theHeaderLengthfieldfromtheTotalPacketLength,theIP softwarewillbeabletodeterminethatthefragment’sdata is64byteslong.Inaddition,theMoreFragmentsflagwill besetto1,indicatingthatmorefragmentsare coming.ThenextfragmentwillthenshowaFragmentationOffsetof64bytes,althoughthiswillbeprovidedinan8-bytemultiplesotheFragmentationOffsetfieldwouldactuallyshowthevalueof8.AftersubtractingtheHeaderSizevaluefromtheTotalPacketSizevalue,theIPsoftwarewilldeterminethatthefragment’sdatais64... GetInternetCoreProtocols:TheDefinitiveGuidenowwithO’Reillyonlinelearning. O’Reillymembersexperienceliveonlinetraining,plusbooks,videos,anddigitalcontentfrom200+publishers. Startyourfreetrial Don’tleaveempty-handed GetMarkRichards’sSoftwareArchitecturePatternsebooktobetterunderstandhowtodesigncomponents—andhowtheyshouldinteract. It’syours,free. Getitnow Close