简介：PIM-SM(ProtocolIndependentMulticast-SparseMode)isamainmulticastroutingpro-tocolintheIPv6(InternetProtocolversion6).Itcanuseeitherasharedtreeorashortestpathtreetodeliverdatapackets,consequentlythemulticastIPlookupenginerequires,insomecases,twosearchestogetacorrectlookupresultaccordingtoitsmulticastforwardingrule,anditmayresultinanewrequirementofdoublingthelookupspeedofthelookupengine.TheordinarymethodtosatisfythisrequirementinTCAM(TernaryContentAddressableMemory)basedlookupenginesistoexploitparallelismamongmultipleTCAMs.However,traditionalparallelmethodsalwaysinducemorere-sourcesandhigherdesigndifficulty.Weproposeinthispaperanovelapproachtosolvethisproblem.ByarrangingmulticastforwardingtableinclasssequenceinTCAMandmakingfulluseoftheintrinsiccharacteristicoftheTCAM,ourapproachcangettherightlookupresultwithjustonesearchandasingleTCAM,whilekeepingthehardwareoflookupengineunchanged.ExperimentalresultshaveshownthattheapproachmakeitpossibletosatisfyforwardingIPv6multicastpacketsatthefulllinkrateof20Gb/swithjustoneTCAMwiththecurrentTCAMchip.