基于web代理缓存技术来提高计算机网络性能的模型研究(IJITCS-V5-N11-5)

I.J.InformationTechnologyandComputerScience,2013,11,42-53PublishedOnlineOctober2013inMECS()DOI:10.5815/ijitcs.2013.11.05Copyright©2013MECSI.J.InformationTechnologyandComputerScience,2013,11,42-53AProposedModelforWebProxyCachingTechniquestoImproveComputerNetworksPerformanceNashaatel-KhameesyProf.andHeadofComputers&InformationsystemsDept-SAMS,MaadyCairo,EgyptE-mail:[e-mail]medComputer&InformationSystemDept-SAMS,MaadyCairo,EgyptE-mail:[e-mail],[e-mail]—oneofthemostimportanttechniquesforimprovingtheperformanceofwebbasedapplicationsiswebproxycachingTechnique.Itisusedforseveralpurposessuchasreducenetworktraffic,serverload,anduserperceivedretrievaldelaysbyreplicatingpopularcontentonproxycachesthatarestrategicallyplacedwithinthenetwork.Theuseofwebproxycachingisimportantandusefulinthegovernmentorganizationsthatprovidesservicestocitizensandhasmanybranchesalloverthecountrywhereitisbeneficialtoimprovetheefficiencyofthecomputernetworksperformance,especiallyremoteareaswhichsufferfromtheproblemofpoornetworkcommunication.Usingofproxycachesprovidesallusersinthegovernmentcomputernetworksbyreducingtheamountofredundanttrafficthatcirculatesthroughthenetwork.Italsoprovidesthembygettingquickeraccesstodocumentsthatarecached.Inaddition,therearealotofbenefitswecanobtainfromtheusingofproxycachesbutwewilladdressthemlater.Inthisresearch,wewillusewebproxycachingtoprovidealloftheabovebenefitsthatwearementionedaboveandtoovercomeontheproblemofpoornetworkcommunicationinENR(EgyptianNationalRailways).Wearegoingtouseaschemetoachievetheintegrationofforwardwebproxycachingandreverseproxycaching.IndexTerms—WebProxyCachingTechnique,Forwardproxy,ReverseProxyI.IntroductionOneofthemostwell-knownstrategiesforimprovingtheperformanceofWeb-basedsystemisWebproxycachingbykeepingWebobjectsthatarelikelytobeusedagaininthefutureinlocationclosertouser.ThemechanismsTheWebproxycachingareimplementedatthefollowinglevels:clientlevel,proxylevelandoriginalserverlevel.[1],[2]itisknownthatproxyserversarelocatedbetweenusersandwebsitesforlesseningoftheresponsetimeofuserrequestsandsavingofnetworkbandwidth.Wealsoshouldbuildanefficientcachingapproachinordertoachievebetterresponsetime.Generally,weusewebProxyserverstoprovideinternetaccesstouserswithinafirewall.Forsecurityreasons,companiesrunaspecialtypeofHTTPserverscalledproxyontheirfirewallmachines.WhenaProxyserverreceivesanyrequestsfromtheclients,itforwardsthemtotheremoteserversinterceptstheresponses,andsendstherepliesbacktotheclients.Duetoweusethesameproxyserversforallclientsinsideofthefirewallinthesameorganization,theseclientssharecommoninterestsandtheywouldprobablyaccessthesamesetofdocumentsandeachclienttendstobrowsebackandforthwithinashortperiodoftime,Sothisprovidestheeffectivenessofusingtheseproxiestocachedocuments.Therefore,thiswillincreasethehitratioforapreviouslyrequestedandcacheddocumentontheproxyserverinthefuture.Inadditiontowebcachingatproxyserversavesnetworkbandwidth,italsoprovidesloweraccesslatencyfortheclients.MostWebproxyserversarestillbasedontraditionalcachingpolicies.ThesetraditionalcachingpoliciesonlyconsideronefactorincachingdecisionsandignoretheotherfactorsthathaveimpactontheefficiencyoftheWebproxycaching.DuetothisreasontheseconventionalpoliciesaresuitableintraditionalcachinglikeCPUcachesandvirtualmemorysystems,buttheyarenotefficientinWebcachingarea.[3],[4]Weusetheproxycacheoftheproxyserveranditislocatedbetweentheclientmachinesandoriginserver.Theworkoftheproxycacheissimilartotheworkofthebrowsercacheinstoringpreviouslyusedwebobjects.Thedifferencebetweenthemisthebrowsercachewhichdealswithonlyasingleuser,theproxyserverserviceshundredsorthousandsofusers.Theworkoftheproxycacheisasfollow,whentheproxyserverreceivesarequestitchecksitscacheatfirstiftheAProposedModelforWebProxyCachingTechniquestoImproveComputerNetworksPerformance43Copyright©2013MECSI.J.InformationTechnologyandComputerScience,2013,11,42-53requestisfoundtheproxyserversendstherequestdirectlytotheclientbutiftherequestisnotfoundtheproxyserverforwardstherequesttotheoriginserverandaftertheoriginserverrepliestotheproxyserveritforwardstherequesttotheclientandalsosaveacopyfromtherequestinlocalcacheforfutureuse.TheproxycachingisusedtoreduceuserdelaysandtoreduceInternetcongestionsitiswidelyutilizedbycomputernetworkadministrators,technologyproviders,andbusinesses.[5],[6],[7]Theproxyserverusesitsfilteringrulestoevaluatetherequest,soitmayuseIPaddressorprotocoltofilterthetraffic.Iftherequestisvalidbythefilter,theproxyprovidesthecontentbyconnectingtotheoriginserverandrequestingtheserviceonbehalfoftheclientincasetherequiredcontentisnotcachedontheproxyserver.TheproxyserverwillreturnthecontentdirectlytotheclientifitwascachedbeforebytheproxyserverWemustconsiderthefollowingproblemsbeforeapplyingwebproxycaching:SizeofCache:Intraditionalarchitectureseachproxyserverkeepsrecordsfordataofallotherproxyservers.Thiswillleadinincreasingincachesizeandifcachesizebecomeslargethiswillbeaproblem