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Mobile IP, or TCP/IP on tour

Distribueradesystem, VT2000Jerry.Eriksson@cs.umu.se

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OutlineWhy Mobility?IP routing, very

shortThe need for Mobile

IP.Mobile IP - OverviewThe Gory DetailsTunneling

Future: Mobility for IPV6

Open Issues TCP performance (RSVP and Real-

Time Traffic) Service Location

Summary and future for Mobile IP

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Mobile IP: A standard for mobile computing and networkingComputers doesn’t

stay put.Change location

without restart its application or terminating any ongoing communication

Example 1: Un-plug at campus, and plug it back at home

Example 2: Un-plug from office, let the wireless network take over

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IP NetworkingProtocol layer

Network Layer Transport Layer

What does IP do moving packets

from source to destination

No ’end-to-end’ guarantees

IP addresses Network-prefix Host portion

IP Routing Packet Header Network-prefix Every node on the

same link has the same network-prefix

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The Need for Mobile IPFig 3.1host Specific Routes (too costly)Node’s IP address (TCP fails)Link layer (Too many standards)

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Mobile IP Solves the following problemsIf a node moves

from one link to another without chnging its IP address, it will be unable to receive packets at the new link; and

If a node changes its IP address when it moves, it will have to terminate and restart any on-going communications each time it moves

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Mobile IP OverviewProposed as a

Standard in November 1996

Solution for Internet Scalable, robust,

secure, maintain communication

Use their permanent IP address

Routing protocol Route packets to

nodes that could potentially change location very rapidly

Layer 4-7, outside Mobile IP, but will be of major interest (TCP, for example)

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Reqiurements for Mobile IP; A node must be able toCommunicate wtih

other nodes after changing its link-Layer attachment to the internet.

Communicate using only its home IP address.

Communicate with other computers not using Mobile IP.

Handle security threats efficiently

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Design goals

Size and and the frequency as small as possible

Simple to implement.Aviod solutions that uses multilpe IP

adresses (Running out of IPv4 adresses

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4.7: Mobile IP Entities and Relationships (Fig. 4-1)Mobile Node (mobilen)Home Agent (Hemagent)Foreign agent (fjärragent)Home link (hemmalänk)Foreign Link (fjärrlänk)care-of-addresses (c/o, besöksadress)

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Home agentA router with an interface on the mobile

node’ home link Node keep the Home agent informed of its current

location (care-of-addresses) Advertises reachability to the network-prefix of

the mobile node’s home adress (Attracting IP adresses)

intercepts packets destined to the mobile node’s home adress and tunnels them to (c/o)

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Foreign AgentA router on a mobile node’s foreign

link which assists the mobile node in informaing its

home agent of its current (c/o) provides (c/o) adress and de-tunnels

packets (sent from the home agent) default router generated by the mobile

node.

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TunnelingAn encapsulating IP packet including a

path and an original IP packetFigure 4-2

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Definitions on ’Home’Home Adress - IP adress permanently

assigned to a mobile node (Does not change)

Home Link - network-prefix of the mobile node’s home address define its home link

Home agent - A router that has at least one interface on the mbile node’s home link

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Definitions on c/oA c/o is specific to the foreign link currently

being visited by a mobile node.A node’s c/o changes every time the mobile

node moves from one foreign link to anotherPackets desitnated to a c/o can be delivered

using existing Internet routing mechanismsA c/o is used as an exit pont of a tunnel from

the home agent toward the mobile node

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4.8: A high Level desription (Fig. 4-3)Home agents and foreign agents advertise their

presence by periodically multicasting (broadcasting) Agent advertisements

Mobile node’s listens to Agent advertisements (I am a home or away)

A mobile node connected to a foreign link acquires a c/o adress

Mobile node registers its c/o address with its home agent

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4.8: A high Level desription (Fig. 4-3) Cont:Home agent adverties reachibility to the netwrok-

prefix of the mobile node’s home link (Attracting packets sent to the mobiles home adress. Intercept these messages and tunnels them to the C/O

At C/O, the original packet is extracted from the tunnel and then delivered to the mobile node

In reverse odirection, packets sent from the mobile node are routed directly to thier destination, without need for tunneling (FA only router)

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5: The gory detailsAgent Discovery

Determines whether it is currently connected to its home link or a foreign link.

Detects whether it has moved from one link to another

obtains a care-of adress when connected to a foreign link

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5.2.1: MessagesAgent advertisements; Used by agents to

announce their capabilities to mobile nodes Agent advertisements are continuously

transmitted (multicast/broadcoast) on a specific link

Allow the mobiles to determine whether any agent is present (gets identities)

Agent solicitations; are sent by mobile that do not have the patience to wait for an Agent advertisment

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5.2.2 How does a mobile node detrmine that is has moved?Using Lifetime: Tells the mobile how soon

it should expect to hear another Agent Advertisment. AA three times faster than Lifetime

Multiple foreign agents

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5.3 What is registration A mobile node

register whenever it detects that it has chnged link from one network to another.

Reregisters when it has not moved, but when it existing registration due to expire.

Mobile IP registration is the process by which a mobile node: requests routing services from a foreign agent or foreign

link informs its home agent of its current care-of-address. Renews a registration due to expire deregisters when it returns to its home link

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5.3.1 Registration scenariosA registration consists of an exchange of a

Registration request and a Registration Reply between a mobile node and its home agent.

Three common scenarios: Using foreign agent c/o Using collocated c/o deregisters upon returning home

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5.3.2 How do nodes Process registrations Se summary

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5.3.3 How can a Mobile learn

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5.3.4. How Does

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5.4: How are the Packets routed

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5.4.6 Why the triangle routing

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5.5 SummaryAgent DiscoveryRegistrationRouting

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Tunneling: 6.1 IP Encapsulation

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Future Topics; Work in progress 12: IPv6 vs IPv4Size adresses: 128 bits vs 32 bits

No real chance of running out of adresses A single newtowrk-prefix route Autoconfigure using very simple

mechanismsLess frequently used fields in IPv4

moved into optionalIPv6 more rigorously defined (more

useful)

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12.2 Relevant to Mobile IP V6Larger adresses - No need for Foreign agents

Collocated C/O is the only one needed, snice there are sufficient IP adresses

New routing Header help Security attack (less options) Very fast forward desicion- not all routers need to

read by every router, Router Discovery Static Address Autoconfiguration -

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12.1.1 HeadersBase: Priority fields, Flow label (Real-time

traffic)Extension headers: Form a chain of

headers

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12.4 How Does it work

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12.5 How does a Mobile ...

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12.6 How Does

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12.8: IP V6 summary

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13: Open Issues. 13.1: TCP Performance and Mobility

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13.1.1: What is TCP

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13.1.2: How does TCP works

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13.1.3: Are TCP’s ..

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13.1.4: How can TCP

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13.2 RSVP and Real-Time Traffic

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13.3 Service Location

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14: SummaryBackgroundTerminologyApplying Mobile IPOpen Issues

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14: The future of Mobile IP