CS 6390 – Advanced Computer NetworksWhat is mobility?Mobility and Standard IP RoutingMobility: VocabularyMobility: more vocabularyMobility: approachesSlide 7Mobile IP - RegistrationMobility via Indirect RoutingIndirect Routing: commentsMobility via Direct Routing (Route Optimization)Mobility via Direct Routing: commentsMobile IP vs IP MulticastCS 6390 – Advanced Computer NetworksIP-MobilityWhat is mobility?spectrum of mobility, from the network perspective:no mobilityhigh mobilitymobile user, usingsame access pointmobile user, passing through multiple access point while maintaining ongoing connections (like cell phone)mobile user, connecting/ disconnecting from network using DHCP.Mobility and Standard IP RoutingIP assumes end hosts are in fixed physical locationsWhat happens if we move a host between networks?IP addresses enable IP routing algorithms to get packets to the correct networkEach IP address has network part and host partThis keeps host specific information out of routersLayer2 is used to get packets to hosts in networksThis still assumes a fixed end hostWhat if a user wants to roam between networks?Mobile users don’t want to know that they are moving between networksWhy can’t mobile users change IP when running an application?Mobility: Vocabularyhome network: permanent “home” of mobile(e.g., 128.119.40/24)Permanent address: address in home network, can always be used to reach mobilee.g., 128.119.40.186home agent: entity that will perform mobility functions on behalf of mobile, when mobile is remotewide area networkcorrespondentMobility: more vocabularyCare-of-address: address in visited network.(e.g., 79.129.13.2) wide area networkvisited network: network in which mobile currently resides (e.g., 79.129.13/24)Permanent address: remains constant (e.g., 128.119.40.186)foreign agent: entity in visited network that performs mobility functions on behalf of mobile. correspondent: wants to communicate with mobileMobility: approachesLet routing handle it: routers advertise permanent address of mobile-nodes-in-residence via usual routing table exchange.routing tables indicate where each mobile locatedno changes to end-systemsLet end-systems handle it: indirect routing: communication from correspondent to mobile goes through home agent, then forwarded to remotedirect routing: correspondent gets foreign address of mobile, sends directly to mobileMobility: approachesLet routing handle it: routers advertise permanent address of mobile-nodes-in-residence via usual routing table exchange.routing tables indicate where each mobile locatedno changes to end-systemsLet end-systems handle it: indirect routing: communication from correspondent to mobile goes through home agent, then forwarded to remotedirect routing: correspondent gets foreign address of mobile, sends directly to mobilenot scalable to millions of mobilesMobile IP - RegistrationEnd result:Foreign agent knows about mobileHome agent knows location of mobilewide area networkhome networkvisited network1mobile contacts foreign agent on entering visited network2foreign agent contacts home agent: “this mobile is resident in my network”Mobile IP: IETF’s proposal for supporting IP mobility in the InternetMobility via Indirect Routingwide area networkhomenetworkvisitednetwork3241correspondent addresses packets using home address of mobilehome agent intercepts packets, forwards to foreign agentforeign agent receives packets, forwards to mobilemobile replies directly to correspondentIndirect Routing: commentsMobile uses two addresses:permanent address: used by correspondent (hence mobile location is transparent to correspondent)care-of-address: used by home agent to forward datagrams to mobileforeign agent functions may be done by mobile itselftriangle routing: correspondent-home-network-mobileinefficient when correspondent, mobile are in same networkHow does the home agent receives packets destined to mobile node?Uses Proxy ARP mechanism to impersonate the mobile to the access routerMobility via Direct Routing (Route Optimization)wide area networkhomenetworkvisitednetwork4251correspondent requests, receives foreign address of mobilecorrespondent forwards to foreign agentforeign agent receives packets, forwards to mobilemobile replies directly to correspondent3Mobility via Direct Routing: commentsovercome triangle routing problemnon-transparent to correspondent: correspondent must get care-of-address from home agentWhat happens if mobile changes networks?Mobile IP vs IP MulticastInteraction between Mobile IP and IP multicast?Can we use ASM based multicast ideas to support IP mobility?Can we use SSM based multicast ideas to support IP
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