Mobility And Mobile I Pv4
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  • 1. Mobility issues
  • 2. Support for Mobility in IP Internetworks
    • Routing done with IP address
    • IP address of device tied to a network
    • No redirection possible for mobile node
    • Routing by
      • Manual configuration
      • Unique address for nodes
  • 3. Mobility support in IPv4
    • Seamless Device Mobility Using Existing Device Address
    • No New Addressing or Routing Requirements
    • Interoperability
    • Layer Transparency
    • Limited Hardware Changes .
    • Scalability
    • Security
  • 4. Mobility overview
    • Implementing a forwarding system for mobile devices
    • When a mobile unit is on its “home” network, it functions normally
    • When it moves to a different network, datagrams are sent from its home network to its new location
    • This allows normal hosts and routers that don't know about Mobile IP to continue to operate as if the mobile device had not moved
    • Special services required to implement Mobile IP:
      • Letting a mobile device determine where it is
      • Telling the home network where to forward messages etc
    • Mobile IP was designed under the specific assumption that the attachment point would not change more than once per second
  • 5. Message forwarding
    • The mobile node’s home router serves as home agent (HA) in Home Network (HN)
    • the router in Foreign Network (FN) as the foreign agent (FA)
    • The mobile has been assigned a temporary, “care-of” address to use while in FN
    • In step #1, the remote client sends a datagram to the mobile using its home address, as before.
    • It arrives in HN as usual.
    • In step #2, the HA encapsulates that datagram in a new one and sends it to the mobile node in FN.
  • 6. Mobile IP operation
  • 7. Mobile IP Devices & Roles
    • Mobile Node: Node on the move
    • Home Agent: This is a router on the home network
    • Foreign Agent: This is a router on the network to which the mobile node is currently attached
    • The HA receives datagrams destined for the MN’s normal IP address and forwards them to the MN’s current location, either directly or by sending to the FA.
    • The HA and FA are also responsible for various communication and setup activities that are required for Mobile IP to work.
  • 8. Gen operation of Mobile IP
    • Agent Communication
      • Agent Discovery process
        • Listens for Agent Advertisement messages
        • Agent Solicitation message
    • Network Location Determination by Mobile node
      • by looking at the information in the Agent Advertisement message.
    • Care-Of Address Acquisition
      • From the foreign Agent Advertisement message
      • Or other means
    • Agent Registration
      • informs the HA on its HN of its presence on the FN
      • registering with the HA
      • This may be done either directly between the MN and the HA, or indirectly using the FA as a conduit.
    • Datagram Forwarding: directly or through FA
  • 9. Home and care of addresses
    • Home address
      • This is the address used by the device on its home network
    • Care-Of Address
      • A secondary, temporary address used by a MN while it is 'traveling” away from its HN
    • Mobile IP Care-Of Address Types
      • Foreign Agent Care-Of Address
        • This is a care-of address provided by a foreign agent in its Agent Advertisement message
        • In fact it is the address of foreign agent itself
        • HA forwards MN’s message to FA
      • Co-located Care-of Address
        • MN acquires by manually in the FN
        • MN acquires from DHCP in FN
  • 10. Agent Discovery Process
    • Agent/Node Communication
    • Orientation
    • Care-Of Address Assignment
  • 11. Mobile IP Messages
    • Agent Advertisement
      • This is a message transmitted regularly by a router acting as a Mobile IP agent.
      • It consists of a regular Router Advertisement message that has one or more extensions added that contain Mobile-IP-specific information for mobile nodes
    • Agent Solicitation Messages
      • This message can be sent by a mobile IP device to nudge a local agent to send an Agent Advertisement.
  • 12. Mobile IP Mobility Agent Advertisement Extension Format
  • 13. Registration
    • Direct Registration ( co-located care-of address )
      • Mobile node sends Registration Request to home agent.
      • Home agent sends Registration Reply back to mobile node.
    • Indirect Registration ( FA care-of address )
      • Mobile node sends Registration Request to foreign agent.
      • Foreign agent processes Registration Request and forwards to home agent.
      • Home agent sends Registration Reply to foreign agent.
      • Foreign agent processes Registration Reply and sends back to mobile node.
  • 14. Registration messages
    • Registration is performed by the mobile node sending a Registration Request message
    • the home agent returns a Registration Reply .
    • The foreign agent may be required to act as a “middleman” to facilitate the transaction, but is otherwise not involved
  • 15. Mobile IP Data Encapsulation
    • The home agent will intercept datagrams intended for the mobile node as they are routed to its home network and forward them to the mobile node.
    • This is done by encapsulating the datagrams and then sending them to the node's care-of address.
    • IP-in-IP is default encapsulation
  • 16. Mobile IP data Delivery tunnel
    • The start of the tunnel is the home agent
    • The end of the tunnel depends on what sort of care-of address is being used:
      • Foreign Agent Care-Of Address:- FA
      • Co-located care-of Address:- Mobile Node
  • 17. Triangle delivery path
    • Normally, the tunnel is used only for datagrams that have been sent to the mobile node and captured by the home agent.
    • When the mobile nodes wants to send a datagram, it doesn't tunnel it back to the home agent; this would be needlessly inefficient.
    • Instead it just sends out the datagram directly using whatever router it can find on its current network, which may or may not be a foreign agent.
    • When it does this, it uses its own home address as the source address for any requests it sends.
    • As a result, any response to those requests will go back to the home network.
    • This sets up a “triangle” of sorts for these kinds of transactions
  • 18. Mobile tunneling Triangle path
  • 19. Mobile IP Reverse Tunneling
    • A reverse tunnel is set up between the mobile node and the home agent, or between the foreign agent and the home agent, depending on care-of address type.
    • All transmissions from the mobile node are tunneled back to the home network where the home agent transmits them over the internetwork
    • A more symmetric operation rather than the “triangle” path
    • This is needlessly inefficient, because it means each communication requires four steps.
    • Thus, it is used only when necessary.
  • 20. Situation for reverse tunneling
    • where network where the mobile node is located has implemented certain security measures that prohibit the node from sending datagrams using its normal IP address.
    • In particular, a network may be set up to disallow outgoing datagrams with a source address that doesn’t match its network prefix.
    • This is often done to prevent “spoofing” (impersonating another’s IP address.)