hepresentnode(Ltypicallyhasthevalue).Theleafsetisusedduringmessageroutingasdescribedinthenextsubsection..RoutingInPastry,messagesareroutedaccordingtoalongestpre-fixmatchprincipleonthedestination’sPastrykey.Ifthekeyofamessageisinrangeofthepresentnode’sleafset,thenthemessageisroutedtothenodewhosenodeIdisclos-esttothekey.Ifthekeyisnotcoveredbythenode’sleafset,itlooksupintheroutingtableanodewhosenodeIdsharesalongerprefixwiththekeythanitsownnodeIdandroutesthemessagetothisnode.Ifthereisnosuchnodethemessageisroutedtoanodethatsharesthesamelengthprefixwiththepresentnode,butisnumericallyclosertothedestinationaddress..NodeArrivalandNodeDepartureAnewnodejoiningtheoverlaynetworkhastoinitializeitsstatetables(i.e.,theroutingtableandtheleafset)andtheninformothersofitspresence.AssumeanodewithnodeIdX.WhennodeXwantstojointhePastrynetworkitfirstlocatesanodeinthenetworkusingforexample“expandingrin将选出那些拥有元数据串返回节点Id,这些元数据串中必须包含所有搜索字。