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Mobile IPv4

Mobile IPv4. Courtesy of Scott Midkiff with Virginia Tech Mary Baker with Stanford (Now HP). Motivation: the changing wireless environment. Explosion in wireless networks/services Some connectivity everywhere Overlapping, heterogeneous networks Small, portable devices

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Mobile IPv4

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  1. Mobile IPv4 Courtesy of Scott Midkiff with Virginia Tech Mary Baker with Stanford (Now HP)

  2. Motivation: the changing wireless environment • Explosion in wireless networks/services • Some connectivity everywhere • Overlapping, heterogeneous networks • Small, portable devices • A choice of network connectivity on one device: wireless technologies convergence

  3. Opportunity for connectivity • New environment gives us opportunity • Continuous connectivity for a mobile host • Seamless movement between networks • Examples • Move from office to elsewhere in building • Move outside building, across campus, to cafe • Why maintain connectivity? • Avoid restarting applications/networks • Avoid losing “distributed/ongoing state”

  4. Different approaches • The traditional approach: support in the network • Intelligence (and expense) is in the network • End-points are cheap (handsets) • Allows for supporting infrastructure • Requires agreements/trust amongst multiple vendors • Examples: • A link/physical level • At routing level • Doesn’t work when switching between technologies and often not between vendors • In Internet, this approach would require modifying lots of routers

  5. Different approaches, continued • The Internet approach: end-to-end • Intelligence (and expense) is in the end-points • Network is cheap (relatively) and as fast as possible • Less work/trust required amongst multiple vendors • End-to-end support at transport/naming/application levels • May be ideal in future, but requires extensive changes • Not currently backwards compatible

  6. Different approaches, continued • Use end-to-end support at routing level • Makes problem transparent at layers above and below • Current Internet standard: Mobile IPv4 (RFC 3344) TCP/IP network stack: application Modify all applications? transport Modify TCP, UDP, etc.? routing Modify IP end-points? link Modify all device drivers? physical How does this work across network technologies?

  7. IP address problem • Internet hosts/interfaces are identified by IP address • Domain name service translates host name to IP address • IP address identifies host/interface and locates its network • Mixes naming and location • Moving to another network requires different network address • But this would change the host’s identity • How can we still reach that host?

  8. MH = mobile host CH = correspondent host Foreign network Home network MH CH Routing for mobile hosts How to direct packets to moving hosts transparently? CH Home network Foreign network MH

  9. ?

  10. Then, let’s use two kinds of addresses For both IPv4 and IPv6 mobility

  11. LD: location directory (address: location)

  12. Mobile IPv4

  13. Three main functions in MIPv4

  14. Mobile IPv4 (RFC 3344) • Leaves Internet routing fabric unchanged • Does not assume “base stations” exist everywhere • Simple • Correspondent hosts don’t need to know about mobility • Works both for changing domains and network interfaces

  15. CH MH Foreign network Home network HA FA Recap Mobile IPv4 –to mobile hosts MH = mobile host CH = correspondent host HA = home agent FA = foreign agent (We’ll see later that FA is not necessary or even undesirable) • FA broadcasts “agent advertisement” message (CoA included) • MH registers new “care-of address” (FA) with HA • HA tunnels packets to FA • FA decapsulates packets and delivers them to MH

  16. Agent advertisement

  17. Agent advertisement

  18. Registration message is application layer!

  19. Registration request

  20. Not ARP !

  21. datagram

  22. Packet addressing Packet from CH to MH Source address = address of CH Destination address = home IP address of MH Payload Home agent intercepts above packet and tunnels it Source address = address of HA Destination address = care-of address of MH Source address = address of CH Destination address = home IP address of MH Original payload

  23. Delivery issues routing

  24. Tunnel management • Tunneling cannot always guarantee delivery • By maintaining “soft state” • MTU of the tunnel (Section 5.1) • TTL (path length) of the tunnel • Reachability of the end of the tunnel • The encapsulator can return accurate ICMP messages to the original sender

  25. If MH comes back to its home network

  26. HA location?

  27. Route optimization(Not in IPv4 mobility spec.) datagram

  28. Foreign network #1 Foreign network #2 CH MH MH FA #1 FA #2 HA Smooth handoff(not in IPv4 mobility spec.) Home network • MH registers new address (FA #2) with HA & FA #1 • HA tunnels packets to FA #2, which delivers them to MH • Packets in flight can be forwarded from FA #1 to FA #2

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