多跳扩展网络NS2.docx
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多跳扩展网络NS2.docx
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多跳扩展网络NS2
AMulti-homingExtensionofWirelessNode
ImplementationinNS-2
QinghuaWang,TingtingZhang
DepartmentofInformationTechnologyandMedia
MidSwedenUniversity,85170Sundsvall,Sweden
Email:
{qinghua.wang,tingting.zhang}@miun.se
Abstract—Duetotherapidgrowthofwirelesscommunication,itisnowbelievedthatwirelessdeviceswithmultipleinterfacesupportwillhighlyincreaseinthenearfuture.IntheresearchcommunityofNetworkSimulator,therehasrecentlybeenquitealargeinterestinextendingthecurrentwirelessnodeimplemen-tationsoastobeabletoincludemorethanoneradiointerfacetoworksimultaneously.
Wefocusoureffortsontheextensionofmulti-homingabilityofns-2,whichhasbeenthemostusednetworksimulatorinwirelessnetworkresearch.Multi-hominghereisdefinedastheabilityofasingleend-pointtosupportmultipleIPaddressesbytheuseofmultipleinterfaces.Thens-2simulationenvironmentisaflexibletoolfornetworkengineerstoinvestigatehowvariousprotocolsperformwithdifferentconfigurationsandtopologies.However,thesupportforwirelessandmobilenetworkinginns-2ismonolithicandnotentirelyconsistentwithbasicdesignprinciplessothatitmakesitquitedifficult,ifnotimpossible,toextendamulti-homingsupportbasedoncurrentmobilenodedesign.Thispaperdescribeshowweextendthens-2frameworktoincludesupportforanimititatedwirelessmulti-homednode.
IndexTerms—Multi-homing,multipleinterfaces,ns-2.
I.INTRODUCTION
Inrecentyearsthetremendoussuccessanddemandmetbywirelesstechnologies,havefosteredaconsiderableamountofresearchworkrangingfrompropagationmodels,radioplanning,powerconsumption,mediumaccess,routingpro-tocolstoQoSandsecurityissues.Topicssuchasmobilead-hocnetworks(MANETsandwirelesssensornetworksforinstancehavebeenthefocusofalotofstudiesandpapersduringthelastfewyears.IntheMANETsandsensornetworkresearchcommunity,alotofstudieshavebeenbasedonthesimulation.Andamongthenetworksimulators,ns-2[1]hasbeenusedinnearlyhalfofthemandbecomeadefactostandard,ifwereferto[6].
Theobject-orienteddesignofns-2allowsforstraightfor-wardcreationanduseofnewprotocols.Thecombinationofeasyinprotocoldevelopmentandpopularityhasensuredthatahighnumberofdifferentprotocolsarepubliclyavailable,despitenotallofwhichareincludedaspartofthesimulator’srelease.ItsstatusasthemostusedMANETssimulatorhasalsoencouragedfurtherpopularity,asdeveloperswouldprefertocomparetheirworktoresultsfromthesamesimulator.However,ns-2iscurrentlynotperfectinsupportingMANETssimulationresearch.Itdoesnotsupportwellforsomeimportantfeatures.Anexampleofsuchafeatureneededtodayisthemulti-homingabilityforawirelessnode.Amulti-homednodeisdefinedasanodethatenjoystheabilityofsupportingmultipleIPaddressessimultaneously,andthiskindofabilityisusuallyimplementedbyaddingmultipleinterfaces,includingwiredandwirelessinterfaces,inasinglenode.Theutilizationofamulti-homednodecanbeversatile.Forexam-ple,thefeatureofredundancyininterfacenumberscanbeusedtoprovidereliabletransmissionandincreasethesurvivabilityofthesessioninthepresenceofnetworkfailures,suchaswhatTheStreamControlTransmissionProtocol(SCTP[3]isdoing.Anotherimportantutilizationistousethemulti-homednodeasacommunicationswitcherinaheterogenousnetwork.Anetworkcanbecomeheterogenousbecauseofdifferentreasons,suchastheneedofthecohabitationbe-tweenanetworkwithupdatedprotocolandanoldnetwork,ornetworkwithnodescomingfromdifferentproviders,orsimplydifferenttypeofnetworksneedingtocommunicate.Inthiscase,themulti-homednodemustpossesstheabilityinforwardingandtranslatingpacketsamongdifferenttypesofconnectednetworks.Asketchgraphofoneheterogenousnetworkinterconnectedbymulti-homednodesisshowninFig.1.
Inthispaper,weextendthecurrentns-2wirelessnodedesigntosupporttheabilityofmulti-homing,soitcanbeusedtoperformthesimulationoftheheterogenouswirelessnetworkinterconnection.
Inthefollowingofthispaper,SectionIIintroducesthens-2wirelessnodedesignandtheexistingeffortsinextendingitsmulti-homingability.SectionIIIfurtherdetailsthewirelessnodedesignincurrentns-2release,whichisthebasisofourmulti-homingextension.SectionIVthengivesthedesigndetailsofourmulti-homingextension.Aninitialns-2imple-mentationofthepresentedmulti-homingextensionisgiveninsectionV.Finally,theconclusionisgiveninsectionVI.
II.RELATEDWORK
Ns-2isthemostpopularsimulationtoolforMANETs.Itbeganasns(NetworkSimulatorin1989withthepurposeofgeneralnetworksimulation.Itswirelessandmobilenet-workingsupportextensionisoriginallydevelopedbyCMUMonarchgroup[2]inthelate1990’sandlaterintegratedinthemainlinecode.Theprimarypurposeofthisextensionwastoenablesimulationofwirelessnetworks,inparticularmultihopadhocnetworks.Thesupportofsensornetworksimulation
MultihomedNode
Fig.1.AninterconnectedheterogenousMANET
inns-2isalsobasedonCMUMonarchextension,withasmallnumberofadd-ons.TheCMUMonarchextensionwillbefurtherdetailedinSectionIIIandourwirelessmulti-homednodeextensionwillbebasedontheCMUMonarchwirelessnodedesign.
Thereisactuallyalreadyonemulti-homingimplementationincludedincurrentns-2release.ItistheimplementationofTheStreamControlTransmissionProtocol(SCTPprovidedbyUniversityofDelaware.However,it’snotasatisfyingsolutionforthemulti-homingrequirementofMANETs.Thefirstargument,againsttheuseofSCTPfortherealizationofmulti-hominginMANETs,isthatthemulti-homingincurrentSCTPimplementationisonlyusedforthetransportredundancybetweenexactlytwoendpoints,anditdoesnotsupporttheinterconnectioninaheterogenousnetwork,whichhoweverisourfocus.Thesecondargumentisthatthemulti-homingfeatureincurrentSCTPimplementationisnotanindependentfeatureandalwaysneedtobeusedtogetherwithSCTP,whichhoweversuppressestheuseofothertransportprotocol,suchasTCPandUDP.ThelastargumentisthatthesupportofSCTPintheexistingInternetinfrastructureandMANETsisminimal.Anextremeexampleistheredundantlydeployedsensornetwork,wheretransmissionreliabilityisnotsoimportantandaconnectionlesstransportprotocolsimilartoUDPispreferredforthesavingoflimitedenergy.
InRef.[5],theauthorstryto(intheformatofahowtoaddressallthechangesthatareneededonns-2sourcecode(bothTCLandC++soastobeabletoextendcurrentwirelessnodeimplementationtosupportmultipleinterfaces.However,inthecurrentwirelessnodestucture,onlyasingleroutingagentcanbeattached.Themanualofns-2[7]saidthatawirelessnodemayhavemorethanoneinterfaces,itisassumedthatauniqueroutingprotocolagentrunsoveralltheinterfaces.WhatRef.[5]canhelpistosupportsuchkindofmultipleinterfaces.Nottomentionmassiveoftechnicalworkneedstobedonetosupportsuchamultipleinterfaceimplementation,suchkindofsupportisnotsufficientfortheinterconnectionrequirementofheterogenousMANETs.
ResearchersintheuniversityNTNUrealizedtheinsuffi-ciencyincurrentns-2wirelessnodedesign,andthoughtthecurrentwirelessnodedesignhasmadeitdifficulttoextendnewfeatures[8].Thustheyprovidedamodifieddesignofns-2wirelessnode,andbasedonthismodifiedwirelessnodedesign,amultipleinterfacewirelessnodewitheachinterfaceattachedwithanindependentroutingagentcanbeeasilybuilt.Thedrawbackisthatthismodifiedwirelessnodedesignisnotincludedinthens-2releasecurrentlyandtherearefewpubliclyavailablemobileprotocolimplementationsthatcansupportthismodifieddesign,althoughitisconsideredtobemorereasonable.
AnotherdrawbackofRef.[5]proposalandNTNUpro-posal[8]isthatalthoughmultipleinterfacescanbesup-portedbytheirproposals,allinterfacesmustsharethesameSource/Sinkagent.Thatmeans,allinterfacesmustsharethesameIPaddress,sinceaSource/SinkagentmustandcanonlybeboundwithastaticIPaddressinthecurrentimplementation.Accordingtothedefinitionofmulti-homing,boththesetwoproposalscannotprovidetherealsensemulti-homingabilityforawirelessnode.
Itmayhoweverbeinterestingtotakealookatthens2-MIRACLEframework[9],wheremultiplemodulesareal-lowedtocoexistwithineachlayeroftheprotocolstack.Thusmulti-homingmaybesupportedusingtheirframework.Inthispaper,wearenotgoingtopresentasubversiveredesignofthens2structure,ratherthanprovideashortcutofimplementingmulti-homednodewithafewadd-ons.
III.CURRENTWIRELESSNODEDESIGNINNS-2
Thissectiongivesabriefoverviewofthewirelessnet-workingsupportinns-2,originallydevelopedasextensionstons-2bytheCMUMonarchgroup[2].Eachwirelessnodeisanindependententitythatisresponsibleforcomputingitsownpositionandvelocityasafunctionoftime,andeachwirelessnodeconsistsofaseriesofcomponents.Basically,thesewirelessnodecomponentsfollowtheISOnetworkstack.Thephysicallayerincludesradiopropagationmodels,radioin-terfaceswithadjustableparameterssuchastransmissionpowerandreceiversensitivityandantennasmodels.Thelinklayerincludesmediumaccesscontrol(MACprotocolsneededinsuchenvironment,andinadditionaddressresolutionprotocol(ARPfortheMACaddresstranslationinanyoutgoingIPpacket.Thenetworklayerareimplementedasaroutingagent.Alltheseentitiesarelinkeduptogetherinsidethewirelessnode.Fig.2showsthebasicschematiclayoutofatypical
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