securityproblemsinthetcpprotocolsuite：在tcp协议的安全问题

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1、SecurityProblemsintheTCPProtocolSuiteTCP/IPPrincipleAndRealizationAlthoughTCP/IPworkstransparentlyfortheuser,occasionallycommunicationsseemtobeslowandTCP/IPissuspectedasthecause・Mostusersareimpatientandexpectthingstohappenrightaway,sodelaysforanyreasonleadtofrustration.Ratherthan

2、sitandwait,mostusersliketobeabletoverifythataconnectiontoaremotemachineisactiveandadelayiscausedbynetworktrafficinsteadofasystemfailure・Attheleast,mostuserswouldliketounderstandwhyasessionisprogressingsiowly.TCP/IPhasseveralutilityprogramsthatprovidestatusinformationandperformanc

3、estatistics・Alsoavailableareseveraldebuggingprogramsandoptionstoenableadeveloperorknowledgeableusertotraceaproblem・Thischapterexaminesthebasicsetofthesetools・AlthoughTCP/IPisastandard,therearemanydifferentimplementationsoftheprotocolfamily.Mostversionshavethebasictoolsetdiscussed

4、today,althoughsomemightalternamesandoutputtotheirownliking・Notallthecommandsshowninthischapterareavailabletoregularusers(asopposedtosystemadministrators)onallsystems,althoughsomesystemadministratorsdoenablesomeaccesstotheutilitiesforcheckingconnectionandTCP/IPstatus・Thecommandsar

5、epresentedheretoshowthedebugginganddiagnosticcapabilitiesavailabletotheTCP/IPuserandadministrator.ThecommandsarenotcoveredinexhaustivedetailbutareintendedtocompletetheTCP/IPpictureforyou.ManyoftheseprogramsandutilitiesareseenagainlaterinthisbookwhenIsetupasampleTCP/IPnetwork・Seve

6、ralfilesareinvolvedinthecompletespecificationofnetworkaddressesandconfigurationforTCP/IP・Forillustrativepurposes,aUNIXsystemisusedasthestandardhere,althoughafewotheroperatingsystemsarementionedasappropriate・Otheroperatingsystemsusedifferentfilenames,butthepurposeofthefilesisusual

7、lythesame・Youmighthavetocheckwithyouroperatingsystemdocumentationtoidentifythefilesusedforeachpurpose・UNIXallowscommentsoneverylineoftheseconfigurationdes,aslongastheyareprefacedbyapoundsign(#)・Ifyouseethischaracterinyourownsystem'sconfiguration"les,youshouldnotethatitisnotpartof

8、anentry.Withmanyoperatingsystems,thedefa