Mobile IP Overview and Discussion

2 Spectrum of Mobility – from network perspective no mobility high mobility mobile user, using same access point mobile user, passing through multiple access point while maintaining ongoing connections ( like cell phone) mobile user, connecting/ disconnecting from network using DHCP.

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

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

5 Mobility: approaches Let routing handle it: routers advertise permanent address of mobile-nodes-in-residence via usual routing table exchange. 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: 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

6 Mobility: approaches Let routing handle it: routers advertise permanent address of mobile-nodes-in-residence via usual routing table exchange. 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: 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

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

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

9 Indirect Routing: comments Mobile uses two addresses: 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 foreign agent functions may be done by mobile device itself triangle routing: correspondent-home-network- mobile triangle routing: correspondent-home-network- mobile –inefficient when correspondent, mobile are in same network

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

11 Indirect Routing: moving between networks suppose mobile user moves to another network 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! Mobility, changing foreign networks is transparent: on going connections can be maintained!

12 Mobility via Direct Routing wide area network homenetwork visitednetwork correspondent requests, receives foreign address of mobile device correspondent forwards to foreign agent foreign agent receives packets, forwards to mobile mobile device replies directly to correspondent 3

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

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

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

16 Mobile IP: registration example visited network: /24 home agent HA: foreign agent COA: COA: …. ICMP agent adv. Mobile agent MA: registration req. COA: HA: MA: Lifetime: 9999 identification:714 …. registration req. COA: HA: MA: Lifetime: 9999 identification: 714 encapsulation format …. registration reply HA: MA: Lifetime: 4999 Identification: 714 encapsulation format …. registration reply HA: MA: Lifetime: 4999 Identification: 714 …. time Message is sent via UDP to port 434.