多跳扩展网络NS2.docx

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