局域网毕业论文文献翻译中英文对照.doc

局域网毕业论文文献翻译中英文对照.doc

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外文资料及中文译文

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