網(wǎng)絡(luò)與通信(chap7-Location Mibility Management(Mobile IP))課件

WirelessCommunicationandNetworkChapter7Location/MibilityManagement1WirelessCommunicationandNetWhydoweneedlocation/mobilitymanagement?Whatislocation/mobilitymanagement?Typesofmobilitymanagement

HandoffmanagementLocationmanagementLocationManagementinGSMConceptofLocationareaLocationupdateprocedureCalldeliveryprocedureOtherlocationmanagementstrategiesLocationupdatePagingDatabasemanagementMobileIPmanagementWhatwewilllearninthischapter:2Whydoweneedlocation/mobiliWhymobilitymanagement?Inwirelinenetworks,thereisafixedrelationshipbetweenaterminalanditsphysicallocationsIncontrast,mobileterminals(MT’s)arefreetotravelandthusitsnetworkaccesspointchangesasitmovesaroundthenetworkcoverageareaTheIDofanMTnolongerprovidesthecurrentlocationinformationoftheMT.Howtokeeptrackofmobileterminals?3Whymobilitymanagement?InwirWhymobilitymanagement?Anexample:cellularnetworkCaller’stelephonetunestothestrongestsignal.Caller’srequestincludesbothherandCallee’stelephonenumbers.BSrelaystherequesttotheswitch.TheswitchcommandsseveralBS’stotransitpagingmessagescontainingCallee’snumber.Callee’sphonerespondstothepagingmessagebyinformingthesystemofitslocation.TheswitchcommandsCaller’sphonetotunetochannelXandCallee’sphonetochannelY.Thecellularphoneconversationstarts.Duringtheconversation,Calleemovestoanewcell.Thesystemrearrangesitselftomaintaintheconversation.WhereiSendbroadcastmessagesfromeverybasestation?4Whymobilitymanagement?AnexaWhatismobilitymanagement?MobilitymanagementisoneofthemostimportantandchallengingproblemsThe

objectiveisforthenetworktodeterminethelocationoftheMTatanytimeforbothmessagedeliveryandmaintainingconnectionsastheMTismovingintoanewareaMaintainlocationinformationasMTs

power-on,move,orpower-offAfunctionatnetworklayerandabove5Whatismobilitymanagement?MoTypesofmobilitymanagementHandoffmanagement(keeptheconnection)Maintainauser’sconnectionastheMTcontinuestomoveandchangeitsaccesspointtothenetwork.Triggeredbyusermobility/roaming,signalstrengthdeterioration(弱化),trafficloadmanagement,etcLocationmanagement(establishthecommunication)Trackingthe

changesoflocationsofMTs.DiscoveringthecurrentlocationoftheMTforcall/messagedelivery.6TypesofmobilitymanagementHaHandoffmanagementThreestagesInitiation

Eithertheuser,anetworkagent,orchangingnetworkconditionsidentifytheneedforhandoffNewconnectiongenerationThenetworkfindresourcesforthehandoffconnectionandperformanyadditionalroutingoperationsData-flowcontrolThenetworkmustmaintainthedeliveryofthedatafromtheoldconnectionpathtothenewconnectionpathaccordingtoagreed-upon(意見一致)

serviceguarantees7HandoffmanagementThreestagesLocationmanagementEverymobilenetworkmanageslocationinformationdifferentlydependingonseveralfactors:typeofofferedservice(calls,messages,etc..)subscriberdensitytrafficofmobileterminalcalls/messagesTwomainmethodsusedformobilitymanagement:methodswithoutlocationupdatingmethodsusinglocationareas8LocationmanagementEverymobilWithoutlocationupdatingNetworkdoesnotknowwheretheMTislocatedWheneveranincomingmessageorcallarrives,sendssearchingmessagesalloverthecoveredareas.TheadvantageissimplicityDisadvantages:LimitedcapacityforincomingcallsLimitedsubscriberdensitypopulation9WithoutlocationupdatingNetwoUsinglocationareasLocationarea(LA)consistsofacertainnumberofcellsorsubnets.MTreportsitscurrentlocationareafromtimetotime-locationupdateNetworkalwaysknowsinwhichlocationareatheMTislocated(vialocationupdating),butitdoesnotknowpreciselywhatcell.Uponthearrivalofanincomingmessage,theMTissearchedonlyinsidethelocationarea.Limitsthecostofresourceutilizationduetolimitingthesearchingtothelocationarea.GSMusesthismethod.10UsinglocationareasLocationaLocationmanagementTwostagesLocationupdate(registration)MTnotifiesthenetworkofitsnewaccesspoint(e.g.,whenitispoweredon,ormovingintonewarea)NetworkauthenticatestheMTandrevisestheMT’slocation.Needlocationinformationstorage.MessagedeliveryNetworkisqueriedfortheMT’slocationprofileandthecurrentpositionoftheMTisfound.Message/callisdeliveredtothefoundlocation.11LocationmanagementTwostages1TwoMajorComponentsLocationUpdateThemobileterminalinformsthesystemitscurrentlocation.PagingThesystemsendsmessages(fromoneormorebasestations)tofindaparticularuser.12TwoMajorComponentsLocationUTwoExtremeCasesLocationneverupdate(nocost).Needtopageeverycells(highcost).Locationupdatesforeverycellcrossing(highcost).Needtopageonlyonecell(lowcost).Locationupdate13TwoExtremeCasesLocationnevePartitiontheregionintodifferentlocationareas.LocationArea14PartitiontheregionintodiffLocationUpdateLA-1LA-2LocationupdateNolocationupdateLocationupdateisperformedwhenthereisaboundarycrossing.HowtodeterminethesizeofaLA?15LocationUpdateLA-1LA-2LocatioLocationDatabasesHomeDatabaseEveryMSispermanentlyassociatedwithahomedatabaseKeeptrackoftheprofileoftheMSMobileID,authenticationkeys,location,etc.VisitingDatabaseKeepstrackoftheMSsinitsservicearea.ThesetwodatabasescommunicatewitheachothertoauthenticateandupdateeachotheraboutthelocationofanMS.GSMTerminology:HomeLocationRegister(HLR)VisitorLocationRegister(VLR)16LocationDatabasesHomeDatabasMSCMSCVLRVLRHLR(1)(2)(3)(4)(6)(5)GSMExample:LocationUpdateMobileSwitchingCenter17MSCMSCVLRVLRHLR(1)(2)(3)(4)(6)LocationUpdateProceduresMStransmitsaLUtothenewBSTheBSforwardstheLUtotheMSCMSCsendsLUtotheHLRandupdatesVLRHLRdoesthefollowing:authenticatetheMSrecordtheIDofthenewVLRsendanACKtothenewVLRHLRsendsaregistrationcancellationmessagetotheoldVLRTheoldVLRremovestherecordoftheMSandreturnsanACKtoHLR18LocationUpdateProceduresMStGSMExample:CallDeliveryMSCMSCVLRVLRHLR(1)(6)(4)(3)(2)(5)MobileSwitchingCenterCallingMSCalledMS(7)19GSMExample:CallDeliveryMSCMCallDeliveryProcedureCallingMSsendsacallinitiationsignaltoMSCthroughBS.MSCsendsalocationrequesttoHLRofthecalledMSHLRdeterminesservingVLRofcalledMSandsendsarouterequestmessagetoit.MSCallocatesatemporaryIDtoMSandsendsthisIDtoHLRHLRforwardstheIDtoMSCofthecallingMSCallingMSCrequestsacallsetuptothecalledMSCPagingmessagesaresenttocellswithintheLA.20CallDeliveryProcedureCallingOtherLocationManagementStrategies21OtherLocationManagementStraPing-PongEffectLA-1AlotoflocationupdatesmaybegeneratedifausercrossesLAboundaryfrequently.22Ping-PongEffectLA-1AlotoflOtherLocationUpdateAlgorithmsTimeBasedEachuserperiodicallyupdateshislocation(e.g.everyhour)MovementBasedEachusercountsthenumberofboundarycrossingsbetweencells.Updateshislocationwhenthisnumberreachesapredefinedvalue,N.DistanceBasedEachusertracksthedistancehehasmoved(innumberofcells)sincethelastupdate.Updateshislocationwhenthedistancereachesapredefinedvalue,N.23OtherLocationUpdateAlgorithMovementBased(N=2)LocationupdateSupposelocationupdateisperformedwhenenteringthiscell.24MovementBased(N=2)LocationDistanceBased(N=2)LocationupdateSupposelocationupdateisperformedwhenenteringthiscell.25DistanceBased(N=2)LocationPageeverycellswithintheLA.Blanket(地毯)Paging26PageeverycellswithintheLAPagethecellssequentiallyuntiltheuserisfound.SequentialPaging1234876591027PagethecellssequentiallyunHowtodeterminepagingorder?Method1:ShortestDistanceFirstPagestheuserstartingfromthecellwherehelastupdatedhislocation.Moveoutwardinashortest-distance-firstorder.Tiesarebrokenarbitrarily.Example:(inahighway)LastLocationUpdate1234528Howtodeterminepagingorder?Howtodeterminepagingorder?Method2:BasedonLocationProbabilityEstimatetheprobabilitythatauserislocatedineachcellwithinthecurrentLA.Pagethecellsindecreasingorderofprobability.Example:(inahighway)LastLocationUpdateABCDESupposeProb.Distributionis:{0.05,0.2,0.4,0.25,0.1}Pagingorder:C,D,B,E,A29Howtodeterminepagingorder?PagingDelayInourpreviousexample,theexpecteddelayisE

[D

]=0.4×1+0.25×2+0.2×3+0.1×4+0.05×1=1.95(pagingcycles)Worst-casedelayis5pagingcycles.Theexpectednumberofcellstobepagedisalso1.95.Worst-case:5cells.30PagingDelayInourpreviousexBlanketPagingvs.SequentialPagingBlanketSequentialPagingcostLargeSmallPagingdelaySmallLargeSequentialgrouppagingmaybeusedifthereisaconstraintonpagingdelay31BlanketPagingvs.SequentialPagegroupsofcellssequentiallyuntiltheuserisfound.SequentialGroupPaging1222333344Worstcasedelayis4cycles.32PagegroupsofcellssequentiaDatabaseManagementLocationUpdateInvolvestheupdatingoflocationdatabasesCallDeliveryInvolvesthequeryingoflocationdatabasesThecostisveryhighiftheMSislocatedfarawayfromitsHLR.e.g.iftheMSisroaminginUSAanditsHLRisinBeijing.33DatabaseManagementLocationUpDatabaseManagementThreeEnhancementMethods:PerUserLocationCachingUserProfileReplicationForwardingPointers34DatabaseManagementThreeEnhanPer-UserLocationCachingEverytimeuserxiscalled,x’slocatoniscachedattheVLRinthecaller’sLA.AnysubsequentcalltoxoriginatedfromthatLAcanreusethisinformation.Noneedtocontactuserx’sHLR.35Per-UserLocationCachingEveryCacheInvalidationEagerCachingWheneverausermovestoanewLA,allcacheentriesforthisuser’slocationareupdated.Locationupdatecostincreasesifausermovesfrequently.LazyCachingCacheupdateisnotperformed.Twocasescanoccur:ahitoramissIncaseofamiss,contacttheHLRthereisanadditionalcost,sincethecachedVLRmustbevisitedfirst.36CacheInvalidationEagerCachinUserProfileReplicationObservation:Eachuserusuallycommunicatesfrequentlywithasmallnumberofsources.Howcanwemakeuseofthisobservation?UserprofilesarereplicatedatselecteddatabasestoreducethecostofqueryingtheHLR.37UserProfileReplicationObservUserProfileReplicationWhenacallisinitiatedfromacertainLA,thecorrespondingMSCdeterminesifareplicationofthecalledMS’suserprofileisavailablelocally.Ifavailable,noHLRqueryisneeded.WhentheMSmovestoanotherlocation,thenetworkupdatesallreplications.38UserProfileReplicationWhenaPointerForwardingEachtimeausermovestoanewLA,aforwardingpointerissetuptoitsperviousVLRtopointtothenewVLR.CallstotheuserwillfirstquerytheHLRtodeterminethefirstVLRandthenfollowthechaintoreachthecurrentVLR.ThelengthofthepointerchainislimitedtoamaximumvalueN.ThismethodcanreducethecostofupdatingtheHLR.39PointerForwardingEachtimeaMobileIP40MobileIP40OutlineHowtosupportInternetmobility?byMobileIP.OurdiscussionwillbebasedonIPv4(thecurrentversion).41OutlineHowtosupportInternetIPAddressIPaddressisa32-bitnumberassignedtoeachnetworkinterfaceofanode.Nodes(suchasrouters)withmultiplenetworkinterfaceshavemultipleIPaddresses.IPAddressinDotted-DecimalNotation42IPAddressIPaddressisa32-bNetworkPrefix;HostPortionAnIPaddresshastwocomponentsNetworkprefixIdentifyingalinkIdenticalforallnodesattachedtothesamelinkHostportionIdentifyingaspecifichostorrouterconnectedtothatlinkExample:6,prefixlength=24Networkprefix=129.61.18Hostportion=2643NetworkPrefix;HostPortionAnMotivations:Withoutspecificsupport,messagedeliveryisnotpossibleformobilehosts(MHs)awayfromitshomeIPsubnet:IProutingisbasedonthenetworkprefixanddestinationIPaddress:Example:6,prefixlength=24Networkprefix=129.61.18Hostportion=26MTcannotchangeIPaddressonmovingtonewIP-subnet–otherwisenotabletodeliverymessages.44Motivations:WithoutspecificsRoutingTableaRouterARouterBRouterCHost1Target/Prefix-LengthNextHopInterface9/32router1a/24router2a/0router3aHost1’sroutingtableHost1wantstoforwardapackettoRulesforRouting:1.Comparetheleft-mostPrefix-LengthbitsofeachTargetwiththeIPdestinationaddress.2.ChoosethematchingroutewiththelargestPrefix-Length.Defaultroute45RoutingTableaRouterARouterB5454aaac5352cc53b52bbbbHost1Host2Host3Host4Host5RouterARouterBRouterCARoutingExample:

Target/Prefix-LengthNextHopInterface/24“direct”a/054aHost1’sroutingtableEthernetANetworkPrefix=1.0.0High-SpeedFiberBackboneNetworkPrefix=3.0.0EthernetBNetworkPrefix=2.0.0EthernetCNetworkPrefix=4.0.04655454aaac5352cc53b52bbbbHost1Host2Host3Host4Host5RouterARouterBRouterCARoutingExample:

Target/Prefix-LengthNextHopInterface/24“direct”a/24“direct”c/2453c/2452cRouterA’sroutingtableEthernetANetworkPrefix=1.0.0High-SpeedFiberBackboneNetworkPrefix=3.0.0EthernetBNetworkPrefix=2.0.0EthernetCNetworkPrefix=4.0.04755454aaac5352cc53b52bbbbHost1Host2Host3Host4Host5RouterARouterBRouterCARoutingExample:

Target/Prefix-LengthNextHopInterface/2454c/24“direct”b/24“direct”cRouterB’sroutingtableEthernetANetworkPrefix=1.0.0High-SpeedFiberBackboneNetworkPrefix=3.0.0EthernetBNetworkPrefix=2.0.0EthernetCNetworkPrefix=4.0.04855454aaac5352cc53b52bbbbHost1Host2Host3Host4Host5RouterARouterBRouterCARoutingExample:

Target/Prefix-LengthNextHopInterface/2454c/24“direct”b/24“direct”cRouterB’sroutingtableEthernetANetworkPrefix=1.0.0High-SpeedFiberBackboneNetworkPrefix=3.0.0EthernetBNetworkPrefix=2.0.0EthernetCNetworkPrefix=4.0.0?495ProblemThepacketisundeliverableHost4isnotconnectedtoEthernetB.RouterBwillthensendaHostUnreachableerrormessagebacktoHost1.Q:Howtosolveit?50ProblemThepacketisundeliverSolution1:Host-SpecificRoutePlacehost-specificroutesintheroutingtablesofRouterA,B,andCasfollows:Target/Prefix-LengthNextHopInterface/3252cTarget/Prefix-LengthNextHopInterface/3252cTarget/Prefix-LengthNextHopInterface/32“direct”bRouterARouterBRouterCQ:Isthisagoodsolution?51Solution1:Host-SpecificRouSolution2:ChangeIPAddressSimplychangetheIPaddressofhost4,asitmovesfromEthernetBtoEthernetC.Forexample,DynamicHostConfigurationProtocol(DHCP)canbeusedtoacquireanewIPaddress.這是我們通常使用的方式！Q:Isthisagoodsolution?52Solution2:ChangeIPAddressSSolution3:MobileIPAstandardproposedtosolvetheproblemofInternetmobility.ItallowsthemobilenodetousetwoIPaddresses:afixedhomeaddressacare-ofaddressthatchangesateachnewpointofattachment53Solution3:MobileIPAstandar引入移動IP的原因主機移動接入位置的變化IP變化無法路由到原來的主機地址上連接中斷54引入移動IP的原因主機移動54移動IP的設(shè)計目標移動節(jié)點在改變數(shù)據(jù)鏈路層接入點后，應(yīng)能夠保持與Internet上其它節(jié)點的連續(xù)通信移動節(jié)點無論連接到任何接入點，應(yīng)該能夠用原來的IP地址進行通信移動節(jié)點應(yīng)該能夠與不具有移動IP的其它節(jié)點進行通信，并且不需要修改這些節(jié)點的協(xié)議移動節(jié)點不應(yīng)該比Internet上的其它節(jié)點面臨更多的安全危險55移動IP的設(shè)計目標移動節(jié)點在改變數(shù)據(jù)鏈路層接入點后，應(yīng)能夠移動IP的功能實體移動節(jié)點（MobileNode）家鄉(xiāng)代理（HomeAgent）外地代理（ForeignAgent）56移動IP的功能實體移動節(jié)點（MobileNode）56Mobile

IPTerminology&Func.MNHAFACNInternetMN,MobileNodeAnIPhostthatmaintainsnetworkconnectivityusingits“home”IPaddress,regardlessofwhichsubnet(ornetwork)itisconnectedtoFA,ForeignAgentProvidesanaddressablepointofattachmenttotheMNcalledCareOfAddress(COA)MaintainsanawarenessforallvisitingMNsActsasa‘relay’betweentheMNanditsHomeAgentReceivesallpacketsfortheMNfromtheMN’sHomeAgentHA,HomeAgentMaintainsanassociationbetweentheMN’s“home”IPaddressanditscareofaddress(loanedaddress)ontheforeignnetworkRedirectsandtunnelspacketstothecareofaddressontheforeignnetworkCN,CorrespondentNodeDestinationIPhostinsessionwithaMobileNodeCOAMN57Mobile

IPTerminology&Func.M常用術(shù)語家鄉(xiāng)地址轉(zhuǎn)交地址外地代理轉(zhuǎn)交地址(ForeignAgentCare-of-Address)配置轉(zhuǎn)交地址(CollocatedCare-of-Address)家鄉(xiāng)網(wǎng)絡(luò)、家鄉(xiāng)鏈路外地網(wǎng)絡(luò)、外地鏈路通信對端節(jié)點移動綁定58常用術(shù)語家鄉(xiāng)地址58隧道(Tunnel)當一個數(shù)據(jù)包被封裝在另一個數(shù)據(jù)包的凈荷中進行傳送時，所經(jīng)過的路徑稱為隧道。圖中還給出了一個例子，表明家鄉(xiāng)代理為將數(shù)據(jù)包傳送給移動節(jié)點，把數(shù)據(jù)包通過隧道先送給外地代理。59隧道(Tunnel)當一個數(shù)據(jù)包被封裝在另一個數(shù)據(jù)包的凈荷中移動IP的工作機制1.通過周期地組播或廣播一個稱為代理廣播（AgentAdvertisements）的消息，家鄉(xiāng)代理和外地代理宣告它們與鏈路的連接關(guān)系。60移動IP的工作機制1.通過周期地組播或廣播一個稱為代理廣播（移動IP的工作機制2.移動節(jié)點收到這些代理廣播消息后，檢查其中的內(nèi)容以確定自己是連在家鄉(xiāng)鏈路還是外地鏈路上。當它連在家鄉(xiāng)鏈路上時，移動節(jié)點就可像固定節(jié)點一樣工作，即它不再利用移動IP的其他功能。61移動IP的工作機制2.移動節(jié)點收到這些代理廣播消息后，檢查其移動IP的工作機制下面的步驟假設(shè)移動節(jié)點連接在一條外地鏈路上。3.連在外地鏈路上的移動節(jié)點需要一個轉(zhuǎn)交地址。它可以從外地代理廣播的代理廣播消息中找到外地代理轉(zhuǎn)交地址，配置轉(zhuǎn)交地址必須通過一個配置規(guī)程得到，比如用DHCP（DynamicHostConfigurationProtocol）、PPP的IPCP或手工配置。62移動IP的工作機制下面的步驟假設(shè)移動節(jié)點連接在一條外地鏈路上移動IP的工作機制4.移動節(jié)點向家鄉(xiāng)代理注冊從第3步中得到的轉(zhuǎn)交地址，可以通過移動IP中定義的消息交換來完成。在注冊過程中，如果鏈路上有一個外地代理，移動節(jié)點就向它請求服務(wù)。為阻止拒絕服務(wù)攻擊，注冊消息要求進行認證。63移動IP的工作機制4.移動節(jié)點向家鄉(xiāng)代理注冊從第3步中得到移動IP的工作機制5.家鄉(xiāng)代理或者是在家鄉(xiāng)鏈路上的其他一些路由器廣播對移動節(jié)點家鄉(xiāng)地址的網(wǎng)絡(luò)前綴的可達性，從而吸引發(fā)往移動節(jié)點家鄉(xiāng)地址的數(shù)據(jù)包，家鄉(xiāng)代理截取這個包（可能用代理ARP），并根據(jù)移動節(jié)點在第4步中注冊的轉(zhuǎn)交地址，通過隧道將數(shù)據(jù)包傳送給移動節(jié)點。6.在轉(zhuǎn)交地址處——可能是外地代理或移動節(jié)點的一個端口，原始數(shù)據(jù)包被從隧道中提取出來送給移動節(jié)點64移動IP的工作機制5.家鄉(xiāng)代理或者是在家鄉(xiāng)鏈路上的其他一些移動IP的工作機制65移動IP的工作機制65MobileIPPacketForwardingTrafficissentasusualtothehomesubnetThehomeagentintercepts(ProxyARP)thetrafficwhilethemobilenodeisregisteredasawayTrafficistunneledtoitscurrentlocationTrafficfromthemobilenodecangodirectlytothecorrespondenthostMobileNodeHomeAgentForeignAgentCorrespondentHostMobileIPPacketForwardingTra代理搜索代理搜索由兩條簡單的消息構(gòu)成代理廣播消息（AgentAdvertisement）代理請求消息（AgentSolicitation）通過ICMP協(xié)議改進實現(xiàn)的67代理搜索代理搜索由兩條簡單的消息構(gòu)成67移動檢測移動檢測：移動節(jié)點確定自己從一條鏈路移到了另一條鏈路上用生存時間域作移動檢測用網(wǎng)絡(luò)前綴作移動檢測68移動檢測移動檢測：移動節(jié)點確定自己從一條鏈路移到了另一條鏈路移動注冊注冊消息

1.注冊請求（RegistrationRequest）

2.注冊應(yīng)答（RegistrationReply）注冊種類

1.移動節(jié)點用外地代理轉(zhuǎn)交地址注冊在一條外地鏈路上

2.移動節(jié)點用配置轉(zhuǎn)交地址注冊在一條外地鏈路上

3.移動節(jié)點在回到家鄉(xiāng)鏈路后進行注銷69移動注冊注冊消息69注冊的種類70注冊的種類70路由71路由71路由優(yōu)化是否可行？72路由優(yōu)化是否可行？72移動IP廣播接收廣播

1.用配置轉(zhuǎn)交地址接收廣播

2.用外地代理轉(zhuǎn)交地址接收廣播家鄉(xiāng)代理必須用多重封裝(NestedEncapsulation)來向注冊了外地代理轉(zhuǎn)交地址的移動節(jié)點發(fā)送廣播包。首先，家鄉(xiāng)代理將廣播包封裝進第一層封裝中，源IP地址為家鄉(xiāng)代理的地址，目的IP地址為移動節(jié)點的家鄉(xiāng)地址。然后，家鄉(xiāng)代理為經(jīng)過第一層封裝的包加上第二層封裝，這時的源IP地址為家鄉(xiāng)代理的地址，目的IP地址為移動節(jié)點的轉(zhuǎn)交地址。73移動IP廣播接收廣播73移動IP廣播發(fā)送廣播

1.送往移動節(jié)點外地鏈路的特定鏈路廣播

2.送往移動節(jié)點家鄉(xiāng)鏈路的特定鏈路廣播

3.特定前綴廣播74移動IP廣播發(fā)送廣播74EntitiesandRelationshipsHomeLink–thelinkhavingthesamenetworkprefixasthenode’sIPaddressMobileNode“athome”HomeAgent–arouteronthemobilenode’shomelink.ForeignAgentForeignAgentForeignLinkForeignLinkMobileNode“visiting”aforeignlink75EntitiesandRelationshipsHomeCare-ofAddressTwoconceptualtypesofcare-ofaddressesForeignagentcare-ofaddressCollocatedcare-ofaddress76Care-ofAddressTwoconceptualForeignAgentCare-ofAddressIPaddressofaforeignagentwhichhasaninterfaceontheforeignlink.TheforeignagentmayhavemorethanoneIPaddress;hence,thenetwork-prefixneednotequalthenetworkprefixoftheforeignlinkThesameaddresscanbesharedbymanymobilenodessimultaneously.77ForeignAgentCare-ofAddressICollocatedCare-ofAddressAnIPaddresstemporarilyassignedtoamobilenode.Itcanbeusedbyonlyonemobilenodeatatime.Thenetworkprefixmustequalthenetworkprefixoftheforeignlink.Itmightbeusedbyamobilenodeinsituationswherenoforeignagentsareavailable.78CollocatedCare-ofAddressAnIThreeMechanismsAgentDiscoveryRegistrationRouting79ThreeMechanismsAgentDiscover1.AgentDiscoveryHomeAgentsandForeignAgentsperiodicallybroadcastsAgentAdvertisements.e.g.onceeveryfewsecondsIfthemobilenodedoesnotwanttowaitfortheperiodicadvertisement,itcanbroadcastAgentSolicitationsthatwillbeansweredbyanyforeignagentthatreceivesit.Mobilenodesdeterminewhethertheyhavemovedfromonelinktoanother.(How?)801.AgentDiscoveryHomeAgentsMoveDetectionAgentAdvertisementhasaLifetimefield.specifyhowsoonamobilenodeshouldexpecttohearanotheradvertisementfromthatsameagent.IfthemobilenodefailstohearanadvertisementfromthatagentwithinthespecifiedLifetime,thenitassumesthatithasmovedtoadifferentlink.81MoveDetectionAgentAdvertisemCare-ofAddressAmobilenodeconnectedtoaforeignlinkacquireaforeignagentcare-of-addressfromtheAgentAdvertisements.Ifmultiplecare-of-addressesarelisted,anyoneofthemcanbeused.Ifaforeignagentisunavailable,themobilenodeobtainacollocatedcare-ofaddressbyDynamicHostConfigurationProtocol(DHCP).82Care-ofAddressAmobilenodecDHCPGoalallowhosttodynamicallyobtainitsIPaddressfromnetworkserverwhenitjoinsanetworkAclient-serverprotocolFour-wayhandshake83DHCPGoal83DHCPClient-ServerScenario7EDHCP

server

arrivingDHCPclientneedsaddressinthisnetworkDHCPrelayagent(typicallyarouter)for223.1.1and223.1.3.ItknowstheaddressofaDHCPserverforthesenetworks.84DHCPClient-ServerScenario223DHCPserver:arrivingclienttimeDHCPdiscoversrc:,68dest.:55,67yiaddr:transactionID:654DHCPoffersrc:,67dest:55,68yiaddrr:transactionID:654Lifetime:3600secsDHCPrequestsrc:,68dest::55,67yiaddrr:transactionID:655Lifetime:3600secsDHCPACKsrc:,67dest:55,68yiaddrr:transactionID:655Lifetime:3600secsChooseanofferifmorethanoneserverreplies.BroadcastAddress:55UDPport67Whatissourceaddress?AllocatesanIPaddressandsetthetimeforwhichtheaddresswillbevalid.85DHCPserver:arriving2.RegistrationRegistrationistheprocessbywhichamobilenoderequestsroutingservicesfromaforeignagent;informsitshomeagentofitscurrentcare-ofaddress;renewsaregistrationwhichisduetoexpire;deregisterswhenitreturnstoitshomelink.862.RegistrationRegistrationisScenario1:RegisteringForeignAgentCare-ofAddressForeignAgentHomeAgent1234Themobilenode,withtheassistanceofaforeignagent,sendsa

RegistrationRequest

withthecare-ofaddressinformation.Whenthehomeagentreceivesthisrequest,itaddsthenecessaryinformationtoitsroutingtable,andsendsaRegistrationReplybacktothemobilenode.MobileNode“visiting”aforeignlink87Scenario1:RegisteringForeigScenario2:RegisteringCollocatedCare-ofAddressHomeAgent1.RegistrationRequestMobileNode“visiting”aforeignlink2.RegistrationReply88Scenario2:RegisteringCollocScenario3:DeregistrationHomeAgent1.(de-)RegistrationRequestMobileNodereturnstoitshomelink2.(de-)RegistrationReply89Scenario3:DeregistrationHomAuthenticationThehomeagentmustbecertainthatregistrationwasoriginatedbythemobilenodeandnotbysomeothermaliciousnode.Registrationofthecare-ofaddressrequiresauthentication.Themobilenodeneedstoproveitsidentitytoitshomeagent.Itisdonebymakinguseofasecretkeyknownonlytothemobilenodeanditshomeagent.90AuthenticationThehomeagentm3.RoutingDifferentScenarios:MobileNode→CorrespondentNodeCorrespondentNode→MobileNodeWithaforeignagentWithoutaforeignagent913.RoutingDifferentScenarios:HowtoSendPacketstoaCorrespondentNode?ForeignAgentHomeAgentCorrespondentMobileNodeSimplyusetheCorrespondent’sIPaddressasthedestinationaddress.Howaboutthesourceaddress?OriginalIPaddress?Care-ofAddress?92HowtoSendPacketstoaCorrHowtoSendPacketstoaMobileNode?ForeignAgentHomeAgentCorrespondentMobileNodeSourceaddressCorrespondent’sIPaddressDestinationaddressMobile’sIPaddress93HowtoSendPacketstoaMobiTunnelingtotheCare-ofAddressForeignAgentHomeAgentMobileNode“visiting”aforeignlinkTunnelHomeAgentinterceptspacketsdestinedtothemobilenode’shomeaddressand

tunnels

themtothemobilenode’scare-ofaddress.ForeignAgentremovesoriginalpacketfromthetunnelanddeliverstheoriginalpackettothemobilenodeovertheforeignlink.94TunnelingtotheCare-ofAddreIPinIPEncapsulationHeaderPayloadOriginalIPpacketIpsrc=OriginalSender Ipdes=Destination’sHomeAddressOuterHeaderOuterPayloadIpsrc=HomeAgent Ipdes=Mobilenode’sCare-ofAddressEncapsulatingIPpacketHeaderPayloadThehomeagentinsertsanewIPheader,ortunnelheader,infrontoftheIPheaderofanydatagramaddressedtothemobilenode’shomeaddress.95IPinIPEncapsulationHeaderPaTriangleRouting移動節(jié)點“訪問”一條外部鏈路ForeignAgentHomeAgent通信對方Whydoesn’tthemobilenodeinformthecorrespondentofitscare-ofaddressandhaveittunneldirectlytothemobilenode?96TriangleRouting移動節(jié)點“訪問”一條外部OptimizedRoutingMobileNode“visiting”aforeignlinkForeignAgentHomeAgentCorrespondentThisispotentiallymoreefficientintermsofdelayandresourceconsumption.Whyisitnotused?97OptimizedRoutingMobileNode“MainObstacle:SecurityMobileNode“visiting”aforeignlinkForeignAgentHomeAgentCorrespondentAbadguysendsafakeregistrationtothecorrespondentItisimpracticaltodistributekeysbetweenamobilenodeandeveryothernodewithwhichitmightcorrespond.98MainObstacle:SecurityMobileEND!99END!99WirelessCommunicationandNetworkChapter7Location/MibilityManagement100WirelessCommunicationandNetWhydoweneedlocation/mobilitymanagement?Whatislocation/mobilitymanage