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USC CSCI 551 - 15_mobileip

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1 Computer Communications - CSCI 551 Copyright © William C. ChengCS551Wireless and MobileNetworkingBill Chenghttp://merlot.usc.edu/cs551-f12cellular vs. ad hocinterference from other radios and obsticals⇒ much less reliableWireless2How Is Wireless & Mobile Different FromTraditional Networking? Computer Communications - CSCI 551 Copyright © William C. Chengtransmission media is airhigher error ratesmitigated by physical level work (coding)not everyone can hear each otherslower speed than traditional (limited spectrum)securitynetwork may not trust usersusers may not trust networklocation change ⇒ routing needs to changewhat basestation are you talking toMobile3How Is Wireless & Mobile Different FromTraditional Networking? (Cont...) Computer Communications - CSCI 551 Copyright © William C. Chenglimited energy (battery)scaling may not be as importantscaling in ad hoc network is open researchsecurity, againnetwork may not trust usersusers may not trust networkone-hop to base-stationvs. ad hoc/multi-hopEx: it may be easier toshare files withfloppiesmobility4Dimensions of Wireless/Mobile Computer Communications - CSCI 551 Copyright © William C. Chengfixed vs. mobilewirelessIP vs. cell phone (3G)vs. protocols for sensornetworksprotocolsenergyconstraintsradio rangeantenna directionalitydo you trust others toforward your datatrustto overhear your packetseven if you haveconnectivity, what canyou do?app-level issuesoften e-mail must gothrough a centralserverlink-layer: MACAWLots of work in mobile/wireless5Approach For This Class Computer Communications - CSCI 551 Copyright © William C. ChengLook at small samplerouting: Mobile IP and DSRtransport-layer: SNOOPapplications (CSci555)sensor network: Direct Diffusion6 Computer Communications - CSCI 551 Copyright © William C. ChengCS551Mobile IP[Johnson96b]Bill Chenghttp://merlot.usc.edu/cs551-f12how do people find you if you move around?Mobile IP:7Key Ideas Computer Communications - CSCI 551 Copyright © William C. Chengspecifically: how do you keep your IP address anywhereyou goImpact on IP addressingHow do we deliver IP packets when endpoints move?8Mobile IP Computer Communications - CSCI 551 Copyright © William C. ChengIssuesImpact on routingScaleKey design considerationsIncremental deploymentInternet standard for support for mobility in IPResult: Mobile IP [RFC 2290]doesn’t scale to millions of hostsWhy not just announce a route to your host?9Possible Approaches Computer Communications - CSCI 551 Copyright © William C. Chengbreaks hierarchical addressing!then people can’t find outWhy not re-address your host?but this is what 95% of people do today, because theyonly run clients, not serverstoo many protocols use IP addresses instead of hostnames,especially for open connectionsWhy not separate naming and addressing?keeps track of where you areA location registry10The IETF Mobile IP Approach Computer Communications - CSCI 551 Copyright © William C. Chengtunnels packets to yougood scalability (many users)Pros:incremental deployment easytriangle routing through homeCons:must be careful about securityis it really necessary? (consider end-to-end argument)11Mobile IP Terminology Computer Communications - CSCI 551 Copyright © William C. ChengHA FACHCorrespondingHost(CH)HomeAgent(HA)ForeignAgent(FA)HomeNetwork(HN)MobileHost(MH)Q:12Discovering Agents Computer Communications - CSCI 551 Copyright © William C. ChengHow do laptops usually figure things out? Why not use that?A: DHCP... because it didn’t exist when Mobile IP started.HA FAMHCHRouters periodically beaconICMP router advertisements13Registration Computer Communications - CSCI 551 Copyright © William C. ChengHA FAMHhomeCH14Registration (Cont...) Computer Communications - CSCI 551 Copyright © William C. ChengHA FAMHhomeCHMHIP=?MH moves to foreign network15Registration (Cont...) Computer Communications - CSCI 551 Copyright © William C. ChengMH registers with FA and gets temp local IP addressHA FAMHhomeCHMHtemp-localFA informs HA so HA always knows16Registration (Cont...) Computer Communications - CSCI 551 Copyright © William C. ChengHA FAMHhomeCHMHtemp-local17Registration (Cont...) Computer Communications - CSCI 551 Copyright © William C. ChengHA setups tunnel to FAHA FAMHhomeCHMHtemp-local18Tunneling Computer Communications - CSCI 551 Copyright © William C. ChengFA gets tunneledpkt, decapsulatesit, sends it toMHtemp-localCH sends pkt to MH’sIP address like normalHA intercepts pkt(uses same IPnetwork as MH) andtunnels pkt to FAMH’s reply can then go straightback to the CHHA FACHMHtemp-localCH does not have to be Mobile IP-awareTriangular routingresulting paths are not optimal, they all go through the HAsmart senders keep cache of FA & MHlocal-tempRoute optimality19Other Mobile IP Issues Computer Communications - CSCI 551 Copyright © William C. Chengone more thing to keep updatedcan be improved with route optimizationdon’t want to drop pkts when changing FAsSmooth handoffsauthenticationSecurity issuesconfidentialityFA may make false claim that MH is in its networkdon’t want others to claim to be MHFA may be listening and recordingFA may modify


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