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tΩbInternetMIntranetܡA~MqtΡANO
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b@ɦUaqbȡAצɳiHiJ~qAұ
AٱoFH˩OΤ򯫯kӱNb~~InternetWbȪ
צb~HSpIUؤPJIޭǩOH
MPĥΤP޳Nh{Ou@Ak_ӥLDO@
qnMw骺զXAuiH@ǯSwƱq𪺤@ݨt@ݡC
q`O~M~Internetߤ@qDAҦpNmb~M
InternetAȴѪ(ISP)ѾA~Ҧ~ɪơAάOq~
InternetiJ~ơAgL𪺽T{A~Cҧ@
T{AOѤ@Ǩƥ]wwWhMFӧA̴MĥΪ
T{q覡Oƫʥ]LoMε{hLo覡AL٦@Ƿs
LokAѦpqhLoMNz𵥡C
@Bƫʥ]LoGƫʥ]Lo(Packet Filter)NL
ʥ](packet)JӦaˬdT{AHפӶiX𪺥qC²檺@ظ
ʥ]LoNOѾ(router)CbѾ|ഫNiH]w֥iH
qLAӽ֤qLCoغ޹Dإ߰_Ӥ
AL{ΦpGOĥάۦPfA|HOFTPɮ׶ǿ骺
AӼ˩A]ӳyF@ӦwW|}Cbq
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ަYѪv覡AΤ@ӰIP}NiHNFoιCثej
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OqMa̤]{AuΫʥ]Loo@kOLkOå
~wC
GBε{hLoGε{hLo(Application Filter)
OݩNzhqD覡AQαMʪ{Ӱ@InternetW{Ϊ
̡AϨ䦨hqD(Gateway)ӱN~M~ɪInternetj}Cˬd
OSIҦ̰hơAi~N~s_ӡCѩoث
@ΦbOSIҦ̰@hA]iHAѩҦLƪqTwAåB
iH[WUدSww\AӬO@ؤw𫬦AL]
@ǯʾѡG
ij
TBqhLoGqhLo(Circuit-level Filter)OGWz
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@ӧsxAA]O̾ڤ@ǳWhӳ]wXJިAO@Ω
ChA]MC@ε{ӯSO]wպAC
~A̪񦳤@طsLo޳NˬdʺAƫʥ]A(state)AoئW
A(statefull inspection)޳Nbd簪hqTwPɡAKNLq
AOUӡCѩ󦳤FAOAtΥiHXǬOq~~o
XqTAȭnDAӭǬO^~oXqTAȪ^ơC
