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Mobile IP

Mobile IP. Overview and Discussion. Mobility: Vocabulary. home network: permanent “home” of mobile (e.g., 128.119.40/24). home agent: entity that will perform mobility functions on behalf of mobile device, when mobile device is remote. wide area network.

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Mobile IP

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  1. Mobile IP Overview and Discussion

  2. Mobility: Vocabulary home network: permanent “home” of mobile (e.g., 128.119.40/24) home agent: entity that will perform mobility functions on behalf of mobile device, when mobile device is remote wide area network Permanent address: address in home network, can always be used to reach mobile e.g., 128.119.40.186 correspondent

  3. Mobility: Vocabulary visited network: network in which mobile currently resides (e.g., 79.129.13/24) Permanent address: remains constant (e.g., 128.119.40.186) Care-of-address: address in visited network. (e.g., 79.129.13.2) wide area network foreign agent: entity in visited network that performs mobility functions on behalf of mobile agent. correspondent hosts: wants to communicate with mobile device

  4. Mobility: approaches • Let routing handle it: routers advertise permanent address of mobile-nodes-in-residence via usual routing table exchange. • routing tables indicate where each mobile node is located • no changes to end-systems • Let end-systems handle it: • indirect routing: communication from correspondent to mobile device goes through home agent, then forwarded to remote • direct routing: correspondent gets foreign address of mobile device, sends directly to mobile device

  5. Mobility: approaches • Let routing handle it: routers advertise permanent address of mobile-nodes-in-residence via usual routing table exchange. • routing tables indicate where each mobile located • no changes to end-systems • Let end-systems handle it: • indirect routing: communication from correspondent to mobile device goes through home agent, then forwarded to remote • direct routing: correspondent gets foreign address of mobile device, sends directly to mobile device not scalable to millions of mobiles

  6. mobile host contacts foreign agent on entering visited network foreign agent contacts home agent: “this mobile is resident in my network” 1 2 Mobility: registration visited network End result: • Foreign agent knows about mobile device • Home agent knows location of mobile device home network wide area network

  7. foreign agent receives packets, forwards to mobile home agent intercepts packets, forwards to foreign agent correspondent addresses packets using home (“permanent”) address of mobile mobile unit replies directly to correspondent 3 2 4 1 Mobility via Indirect Routing visited network home network wide area network

  8. Indirect Routing: comments • Mobile uses two addresses: • permanent address: used by correspondent (hence mobile location is transparent to correspondent hosts) • care-of-address: used by home agent to forward datagrams to mobile device • foreign agent functions may be done by mobile device itself • triangle routing: correspondent-home-network-mobile • inefficient when correspondent, mobile are in same network

  9. foreign-agent-to-mobile packet packet sent by home agent to foreign agent: a packet within a packet dest: 128.119.40.186 dest: 128.119.40.186 dest: 128.119.40.186 packet sent by correspondent dest: 79.129.13.2 Forwarding datagrams to remote mobile via Tunneling Permanent address: 128.119.40.186 Care-of address: 79.129.13.2

  10. Indirect Routing: moving between networks • suppose mobile user moves to another network • registers with new foreign agent • new foreign agent registers with home agent • home agent update care-of-address for mobile • packets continue to be forwarded to mobile (but with new care-of-address) • Mobility, changing foreign networks is transparent: on going connections can be maintained!

  11. foreign agent receives packets, forwards to mobile mobile device replies directly to correspondent 4 2 4 1 3 Mobility via Direct Routing correspondent forwards to foreign agent visited network home network wide area network correspondent requests, receives foreign address of mobile device

  12. Mobility via Direct Routing: comments • overcomes triangle routing problem • non-transparent to correspondent: correspondent must get care-of-address from home agent • What happens if mobile node changes networks?

  13. Mobile IP • RFC 3344 (August 2002) - three main components of standard: • agent discovery • registration with home agent • routing considerations

  14. Mobile IP: agent discovery • agent advertisement: foreign/home agents advertise service by broadcasting ICMP messages (typefield = 9) 16 0 8 24 type = 9 checksum code = 0 H,F bits: home and/or foreign agent standard ICMP fields router address R bit: registration required type = 16 length sequence # RBHFMGrT registration lifetime reserved bits mobility agent advertisement 0 or more care - of - extension addresses

  15. Mobile IP: registration example visited network: 79.129.13/24 home agent foreign agent ICMP agent adv. HA: 128.119.40.7 COA: 79.129.13.2 Mobile agent MA: 128.119.40.186 COA: 79.129.1 3.2 …. registration req. registration req. COA: 79.129.13.2 HA: 128.119.40.7 Message is sent via UDP to port 434. COA: 79.129.13.2 MA: 128.119.40.186 HA: 128.119.40.7 Lifetime: 9999 MA: 128.119.40.186 identification:714 Lifetime: 9999 …. identification: 714 encapsulation format …. registration reply registration reply time HA: 128.119.40.7 MA: 128.119.40.186 HA: 128.119.40.7 Lifetime: 4999 MA: 128.119.40.18 6 Identification: 714 Lifetime: 4999 encapsulation format Identification: 714 …. ….

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