Mobile IP

IP

Cellular Network

Internet

212.10.123.23 180.4.34.12

IP address is used by router to direct data packet to it’s destination. IP address works well if user is static.

If User is moving while active session, How to handle it?

Addressing

Mobile IP

The IP addresses are designed to work with stationary hosts because part of the address defines the network to which the host is attached.

Addressing

Mobile IP

Possible Solution

Keep Up – address and update routing tables. Not feasible to update all routers every time whenever host moves to a new network

Get a New IP This requires that configuration files are changed. Ongoing transmission will be interrupted.

Two addresses - Home address - Care 0f address

Mobile IP

Mobile IP

Home Address: Mobile host original home address.

Internet

182.12.11.0/24

182.12.11.78/24

13.10.0.0/16

13.10.121.11/16

Care of address: Mobile host original home address.

Mobile IP adds mobility support to the Internet network layer protocol IP.

The Internet started at a time when no-one had a concept of mobile computers.

The Internet of today lacks mechanisms for the support of users traveling through the world.

IP is the common base for thousands of applications and runs over dozens of different networks; this is the reason for supporting mobility at the IP layer.

Mobile IP

Addressing

Mobile IP

Mobile IP has two addressing

The home address is permanent;

The care-of address changes as the mobile host moves from one network to another.

Terminology

Mobile Node (MN)system (node) that can change the point of connection to the network without changing its IP address

Home Agent (HA)system in the home network of the MN, typically a router registers the location of the MN, tunnels IP datagrams to the COA

Foreign Agent (FA)system in the current foreign network of the MN, typically a router forwards the tunneled datagrams to the MN, typically also the default router of the MN

Care-of Address (COA)address of the current tunnel end-point for the MN (at FA or MN)actual location of the MN from an IP point of view

Correspondent Node (CN)communication partner

Addressing

Mobile IP

How these addresses are converted into each other?Who will handle these addressing to provide communication services without interruption?

Agent

Mobile IP

Agent provide transparent change in address.

Home Agent.

Foreign Agent.

Home Agent & Foreign Agent

Mobile IP

12

(current physical network for the MN)

home network

(physical home networkfor the MN)

• Example network

Internet

router

HAMN

router

FA foreign network

routerend-system

CN

Communication

13

• Data transfer to the mobile system

Internethome network

foreignnetwork

FA

HA

MN

receiver

1

2

3

sender

CN

1. Sender sends to the IP address of MN, HA intercepts packet2. HA tunnels packet to COA, here FA, by encapsulation3. FA forwards the packet to the MN

Communication

14

foreignnetwork

home network

• Data transfer from the mobile system

Internet

HA

MN

sender

receiver

CN

1. Sender sends to the IP address of the receiver as usual, FA works as default router

FA

1

Communication

Mobile host to Remote host communication

Mobile IP

To communicate with remote host, mobile host requires three phases.

1. Agent Solicitation

2. Registration

3. Data Transfer

16

Mobile hostafter move Remote host

Time Time Time Time Time

Mobile hostwhen at home

Foreign agentHome agent

Mobile IP

Mobile host to Remote host communication

Agent AdvertisementHA and FA periodically send advertisement messages into their physical subnetsMN listens to these messages and detects, if it is in the home or a foreign network (standard case for home network)MN reads a COA from the FA advertisement messages

Registration (always limited lifetime!)MN signals COA to the HA via the FA, HA acknowledges via FA to MN these actions have to be secured by authentication

AdvertisementHA advertises the IP address of the MN (as for fixed systems), i.e. standard routing informationRouters adjust their entries, these are stable for a longer time (HA responsible for a MN over a longer period of time)Packets to the MN are sent to the HA, independent of changes in COA/FA

Mobile host to Remote host communication

Remote host to mobile host communication

Mobile IP

Homeagent

Foreignagent

Mobile hostoriginal home

Remotehost

Mobilehost

Internet

Home network

Foreign network

Remote network

2

1

3

Inefficiency in Mobile IP-Double Crossing

Mobile IP

Homeagent

Foreignagent

Remotehost

Could-bepath

Mobilehost

Internet

Homenetwork

Foreign network

1

2

Communication involving mobile IP can be inefficient. The inefficiency can be severe or moderate. The severe case is called double crossing or 2X . The moderate case is called triangle routing or dog-leg routing.

Mobile IP

Inefficiency in Mobile IP-Triangle routing

Homeagent

Foreignagent

Remotehost

Could-bepath

Mobilehost

Internet

Homenetwork

Foreign network

Remote network

1

2

3

Sender sends all packets via HA to MN higher latency and network loadSolutions – optimization HA informs a sender about the location of MN . Sender learns the current location of MN

direct tunneling to this locationbig security problems!

Questions

Q. Explain when mobile IP is needed Q. Why and where is encapsulation needed for mobile IP?Q. Explain packet flow if two mobile nodes communicate and both are in foreign networks. What additional routes do packets take if reverse tunnelling is required?Q. What is meant by tunnelling? Explain how tunnelling works for mobile IP using IP-in-IP. Discuss the advantages and disadvantages of this method.Q. Name the inefficiencies of mobile IP regarding data forwarding from a correspondent node to a mobile node. What are optimizations and what additional problems do they cause? Q. What are general problems of mobile IP regarding security? Q. What is the basic purpose of DHCP? Name the entities of DHCP. Q. How can DHCP be used for mobility and support of mobile IP?