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IP Mobility SupportNetwork Support for MobilityTwo Tier AddressingPowerPoint PresentationArchitecture contd: Forwarding AgentArchitecture contd: Location DirectoryArchitecture contd: Address TranslationArchitecture Contd: Packet ForwardingMobile IPv4: RFC2002Slide 10Basic ConceptsProtocol OverviewAgent DiscoveryRegistrationRegistration OverviewRouting ConsiderationObtain co-located care-off address via DHCPSummaryMobile IP with Route OptimizationMobile IP with Route Optimization (contd)IPv6 Mobility ProposalOverview of Mobile IPv6Fast HandoverIdea behind fast handoverIP Mobility Support•Basic idea of IP mobility managementunderstand the issues of network-layer mobility support in IP networkunderstand the basic design principles underlying all mobility support schemes•Internet standard: mobile IPv4, Mobile IPv6the operations of MIPv4introduction to MIPv6•Fast handover solutionsNetwork Support for Mobility•In TCP/IP, the host address plays two roles:acts as an end-point identifier for connections involving the host•a host address should always remain the sameprovides routing info for packets destined for the host•a host address should change whenever the host moves•Goal: support mobility without having to change the protocols in all the millions of hosts currently on the InternetTwo Tier Addressing•We need an address p air to identify a MH at any time:Home address for identificationcurrent address for routing•How to do two-tier addressing:not physically done (which requires 8 bytes of address per host)perform address translation along the way by some specialized agents that cache both addresses.A Generic Network Layer Architecture to Support Mobility•Mobile host (MH): a host that moves•Home address (HA): a location-independent address for a MH •Home network: the network identified by the net id part of the HA of MH. A home net has some special agents for proxy-arp, packet forwarding, address translation etc. to support mobility•When a MH moves within its home network, no network-level support is needed since packet forwarding is achieved by bridges•When a MH moves across networks, the HA cannot be used for routing, though the HA has to be used for end-point identification by TCPArchitecture contd: Forwarding Agent•Current address must refer to the foreign network when a MH is in a foreign network•Packets destined for the MH contain the address of a Forwarding Agent (FA).•FA forwards packets to the MHIf FA and MH are directly connected, FA simply replaces the destination address with the Home Address of the MHotherwise, FA has to forward the packet to other FAs till the packet reaches the MH•Note that the router/agent that is the last hop to the MH must be mobility aware, since it has to do the final address translation from FA to MHexample: base stations act as FAsArchitecture contd: Location Directory•Location directory (LD) provides the mapping between the home address and forwarding address for a MH•MH is responsible for sending updates to the LD when it moves•LD is distributed•Typically, the Home network maintains LD for its MHs, though parts of the LD are allowed to be cached by other foreign networksArchitecture contd: Address Translation•When a source communicates with a MH, the MH puts its HA in the destination address field.•Somewhere along the route, this has to pass thru an address translation agent (ATA), which converts the HA to the forwarding address.•Address Translation can be provided by 2 mechanisms:IP-IP Encapsulation: encapsulate the original datagram within another datagram that contains the FA addressLoose source routing: indicates intermediate hops over which the datagram must travel to the final destination. In this case, the intermediate hop will be the FA, which then converts the packet address to the final destinationArchitecture Contd: Packet Forwarding•Source sends out packets that are addressed to HA of MH•ATA intercepts packets and maps HA to FA (using IPIP or LSR)•Packets arrive at FA•FA remaps address to HA and delivers packets over the last hop•At the MH, the packet seems to arrive from Source to HA; thus, transport layer is provided transparency•What if the final FA and the MH were co-located ? Optimizations in this case ?Mobile IPv4: RFC2002•Macro-management for mobilityless frequent than once per secondMore concerned about long-term performance: whether to allow seamless mobility or not•Two scenarios for packet forwarding:MH to a static host: as usuala static host to a MH: needs Mobile IPA Quick Mapping for Mobile IPv4 to the Architecture•Forwarding agent: co-located with foreign Agent or with MH (if DHCP is used)•Location Directory: at home router only•Address Translation Agent: co-located with home router•location update protocol: caching of LD is not allowed; when a MH moves, only the primary copy is modifiedBasic Concepts•Home agent: a router on a MH’s home network which tunnels datagrams for delivery to the MH when it is away from home, maintains LD for MH•Foreign agent: a router on a MH’s visited network which provides routing services to the MH while registered. FA detunnels and delivers datagrams to the MH that were tunneled by the MH’s HA. •Care-of Address: termination point of a tunnel toward a MH, for datagrams forwarded to the MH while it is away from home.Foreign agent care-of address: the address of a foreign agent that MH registers withco-located care-of address: an externally obtained local address that a MH gets.Protocol Overview•Mobility agents (FAs & HAs) advertise their presence•MH receives the agent advertisements & determines whether it is on its home net or a foreign netHome net: MH operates without mobility serviceForeign net: obtains a care-of address on the foreign net (via FA’s agent advertisements or DHCP)•if away from home, MH registers its new care-of address with its HA thru a registration request/response process (possibly via a FA).•Datagram sent to the MH’s home address: intercepted by its home agent, tunneled by the HA to the MH’s care-of address, detunneled at the tunnel endpoint (either a FA or MH itself), and finally delivered to the MH•In the reverse direction, using standard IP routing.Agent Discovery•Method used by a MH to determine whether it is in its home net or a foreign net; may allow MH to determine the foreign


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UCLA COMSCI 211 - IP Mobility Support

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