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院系名称信息科学与技术学院
学生姓名
学生学号__200503013098
专业班级_计科03-7
指导教师
10
外文资料
出处:
计算机世界报第03期C20
ALANmaybecreatedbasedonapeeringoraclient-server.SmallLANsareoftencreatedbasedonasimplepeeringrelationship.Usersmayshareresourcesandcommunicatewithoneanotheronapeernetwork,butnosinglecomputercontrolsapeernetwork,andpeernetworkusersdonottypicallycentralizefilesononemachine.Asarule,peernetworkstendtolackorganizationandadequatesecuritycontrols.
Theclient-serverarchitectureisusuallyusedforsevercontrolsnetworkaccessandnetworkresources.Clientsrequestresourcesfromtheserver,andtheserverprovidesresourcestoclients.ServersmayrangeincomplexityfrommainframestoPCs.ClientsmayrangeincomplexityfromPCstodisplaytoterminals(DTS).Client-Servernetworksprovidestrongcentralsecurity,centralizedfileorganizationandstorage,andcentralizeddatapreservation.Comparedtoapeernetwork,aclient-servernetworkrequiresmorecentralizedandspecializedadministration.
Alongwiththerapidscientificandtechnologicaldevelopment,computeruseinproductionasaproportiongrowing,increasinglyplayadecisiveroleintheministry,theofficehascomputers,greatlyfacilitatethedepartment'
swork,anotherdemandgraduallyrevealthemselves.Thatisthesingletransmissionofinformationbetween.Computernetworksshouldbeestablishedassoonaspossibleontheagenda.Establishcomputernetworksmainpurposeistorealizea"
resourcesharing"
thatallnetworkuserscanenjoythecomputersystemsofallorpartoftheresources.
LANarecurrentlyusedtobroadcastthetechnicalbasisforEthernet,anytwonodesofcommunicationbetweenthedatapacketisnotonlythesetwonodesbythecardreceipt,werealsoatthesameEthernettothenodesofanetworkcardbytheinterception,AslongashackersaccesstotheEthernetnodesforaninterception,cancapturetheEthernetinthedatapacketandallitspacketanalysissolution,therebystealingcriticalinformation,ThisistheEthernetinherentsecurityrisks.Infact,manyontheInternetfreeofthehackingtoolsareputEthernetinterceptionasthemostfundamentalmeans.
Afirewallisanetworkdevicethatenforcessecuritypolicyfornetworktraffic.Thetermoriginatesfromfirewall,afireproofwallusedasabarriertopreventthespreadoffire.AnInternetfirewallcreatesabarrierbetweenseparatenetworksbyimposingapointofcontrolthattrafficneedstopassbeforeitcanreachadifferentnetwork.Afirewallmaylimittheexposureofhoststomaliciousnetworktraffic,e.g.,remoteadversariesattemptingtoexploitsecurityholesinvulnerableapplications,bypreventingcertainpacketsfromenteringnetworksprotectedbythefirewall.
Wheninspectinganetworkpacket,afirewalldecidesifitshoulddroporforwardthepacket.Thedecisionisbasedonafirewall'
ssecuritypolicyanditsinternalstate.Beforeforwardingapacket,afirewallmaymodifythepacket'
scontent.Packetinspectionmayoccuratseveraldifferentlayers:
(1)Thelinklayerprovidesphysicaladdressingofdevicesonthesamenetwork.Firewallsoperatingonthelinklayerusuallydroppacketsbasedonthemediaaccesscontrol(MAC)addressesofcommunicatinghosts.
(2)ThenetworklayercontainstheInternetprotocol(IP)headersthatsupportaddressingacrossnetworkssothathostsnotonthesamephysicalnetworkcancommunicatewitheachother.
(3)Thetransportlayerprovidesdataflowsbetweenhosts.OntheInternet,thetransmissioncontrolprotocol(TCP)andtheuserdatagramprotocol(UDP)areusedforthispurpose.Mostfirewallsoperateatthenetworkandtransportlayer.TCPprovidesreliabledataflowbetweenhosts.UDPisamuchsimplerbutunreliabletransportprotocol.
(4)Theapplicationlayercontainsapplicationspecificprotocolslikethehypertexttransferprotocol(HTTP).Inspectionofapplicationspecificprotocolscanbecomputationallyexpensivebecausemoredataneedstobeinspectedandmorestatesarerequired.
Afirewallisapieceofsoftwareorhardwarethathelpsscreenouthackers,viruses,andwormsthattrytoreachyourcomputerovertheInternet.Ifyouareahomeuserorsmall-businessuser,usingafirewallisthemosteffectiveandimportantfirststepyoucantaketohelpprotectyourcomputer.
ItisimportanttohaveafirewallandantivirussoftwareturnedonbeforeyouconnecttotheInternet.
Ifyourcomputerisnotprotectedwhenyouconnectto