Mobile IPMobile IP

Overview Overview and and DiscussionDiscussion

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Mobility: VocabularyMobility: Vocabularyhome network: permanent “home” of mobile(e.g., 128.119.40/24)

Permanent address: address in home network, can always be used to reach mobilee.g., 128.119.40.186

home agent: entity that will perform mobility functions on behalf of mobile device, when mobile device is remote

wide area network

correspondent

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Mobility: VocabularyMobility: Vocabulary

Care-of-address: address in visited network.(e.g., 79.129.13.2)

wide area network

visited network: network in which mobile currently resides (e.g., 79.129.13/24)

Permanent address: remains constant (e.g., 128.119.40.186)

foreign agent: entity in visited network that performs mobility functions on behalf of mobile agent.

correspondent hosts: wants to communicate with mobile device

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Mobility: approachesMobility: approaches Let routing handle it: Let routing handle it: routers advertise routers advertise

permanent address of mobile-nodes-in-permanent address of mobile-nodes-in-residence via usual routing table exchange.residence via usual routing table exchange.– routing tables indicate where each mobile routing tables indicate where each mobile

node is locatednode is located– no changes to end-systemsno changes to end-systems

Let end-systems handle it: Let end-systems handle it: – indirect routing:indirect routing: communication from communication from

correspondent to mobile device goes through correspondent to mobile device goes through home agent, then forwarded to remotehome agent, then forwarded to remote

– direct routing:direct routing: correspondent gets foreign correspondent gets foreign address of mobile device, sends directly to address of mobile device, sends directly to mobile devicemobile device

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Mobility: approachesMobility: approaches Let routing handle it: Let routing handle it: routers advertise routers advertise

permanent address of mobile-nodes-in-permanent address of mobile-nodes-in-residence via usual routing table exchange.residence via usual routing table exchange.– routing tables indicate where each mobile routing tables indicate where each mobile

locatedlocated– no changes to end-systemsno changes to end-systems

Let end-systems handle it: Let end-systems handle it: – indirect routing:indirect routing: communication from communication from

correspondent to mobile device goes through correspondent to mobile device goes through home agent, then forwarded to remotehome agent, then forwarded to remote

– direct routing:direct routing: correspondent gets foreign correspondent gets foreign address of mobile device, sends directly to address of mobile device, sends directly to mobile devicemobile device

not scalable

to millions of mobiles

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Mobility: registrationMobility: registration

End result:End result: Foreign agent knows about mobile deviceForeign agent knows about mobile device Home agent knows location of mobile deviceHome 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”

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Mobility via Indirect RoutingMobility via Indirect Routing

wide area network

homenetwork

visitednetwork

3

2

41

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

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Indirect Routing: commentsIndirect Routing: comments Mobile uses two addresses:Mobile uses two addresses:

– permanent address:permanent address: used by correspondent used by correspondent (hence mobile location is (hence mobile location is transparenttransparent to to correspondent hosts)correspondent hosts)

– care-of-address:care-of-address: used by home agent to used by home agent to forward datagrams to mobile deviceforward datagrams to mobile device

foreign agent functions may be done by mobile foreign agent functions may be done by mobile device itselfdevice itself

triangle routing:triangle routing: correspondent-home-network- correspondent-home-network-mobilemobile– inefficient when inefficient when correspondent, mobile correspondent, mobile are in same networkare in same network

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Forwarding datagrams to remote Forwarding datagrams to remote mobile via Tunnelingmobile via Tunneling

Permanent address: 128.119.40.186

Care-of address: 79.129.13.2

dest: 128.119.40.186

packet sent by correspondent

dest: 79.129.13.2 dest: 128.119.40.186

packet sent by home agent to foreign agent: a packet within a packet

dest: 128.119.40.186

foreign-agent-to-mobile packet

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Indirect Routing: moving between Indirect Routing: moving between networksnetworks suppose mobile user moves to another suppose mobile user moves to another

networknetwork– registers with new foreign agentregisters with new foreign agent– new foreign agent registers with home agentnew foreign agent registers with home agent– home agent update care-of-address for home agent update care-of-address for

mobilemobile– packets continue to be forwarded to mobile packets continue to be forwarded to mobile

(but with new care-of-address)(but with new care-of-address) Mobility, changing foreign networks is Mobility, changing foreign networks is

transparent: transparent: on going connections can on going connections can be maintained!be maintained!

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Mobility via Direct RoutingMobility via Direct Routing

wide area network

homehomenetworknetwork

visitedvisitednetworknetwork

4

2

41correspondent 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

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Mobility via Direct Routing: Mobility via Direct Routing: commentscomments

overcomes triangle routing problemovercomes triangle routing problemnon-transparent to correspondent:non-transparent to correspondent:

correspondent must get care-of-correspondent must get care-of-address from home agentaddress from home agent– What happens if mobile node changes What happens if mobile node changes

networks?networks?

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Mobile IPMobile IP

RFC 3344RFC 3344 (August 2002) - three (August 2002) - three main components of standard:main components of standard:– agent discoveryagent discovery– registration with home agentregistration with home agent– routing considerationsrouting considerations

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Mobile IP: agent discoveryMobile IP: agent discovery agent advertisement:agent advertisement: foreign/home foreign/home

agents advertise service by agents advertise service by broadcasting ICMP messagesbroadcasting ICMP messages (typefield = (typefield = 9)9)

RBHFMGrT bits

type = 16

type = 9 code = 0

checksum

router address

standardstandard ICMP fieldsICMP fields

mobility agent mobility agent advertisement advertisement

extensionextension

length sequence #

registration lifetime

0 or more care-of-addresses

0 8 16 24

R bit: registration required

H,F bits: home and/or foreign agent

reserved

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Mobile IP: registration Mobile IP: registration exampleexample

visited network: 79.129.13/24 home agent

HA: 128.119.40.7 foreign agent

COA: 79.129.13.2 COA: 79.129.13.2

….

ICMP agent adv. Mobile agent MA: 128.119.40.186

registration req.registration req.

COA: 79.129.13.2 HA: 128.119.40.7 MA: 128.119.40.186 Lifetime: 9999 identification:714 ….

registration req.registration req.

COA: 79.129.13.2 HA: 128.119.40.7 MA: 128.119.40.186 Lifetime: 9999 identification: 714 encapsulation format ….

registration reply registration reply

HA: 128.119.40.7 MA: 128.119.40.186 Lifetime: 4999 Identification: 714 encapsulation format ….

registration reply registration reply

HA: 128.119.40.7 MA: 128.119.40.186 Lifetime: 4999 Identification: 714

….

time

Message is sentvia UDP to port434.