Mobile IP

Seamless connectivity for mobile computers

Problem definition

• IP combines routing information with

host identification in a globally unique IP address.

• On mobility it needs to get a new IP address to indicate the new point of attachment to router.

Problem definition

• TCP uses IP internally to maintain connection state for connections being operated by mobile computer.

• On IP change connection status cannot be maintained.

• Reason :

IP used for both routing & host identification.

Issues of mobile IP

• Compatibility

co-work with wired infrastructure.

• Scalability

Support large number of users.

• Transparency

No difference in wired or wireless domain.

Terminologies

• MN – Mobile Node ,requiring mobility support.

• CN - Correspondent Node, a node to which MN communicates.

• FA - Foreign agent, currently connected router.

• HA – Router corresponding to MN IP’s Subnet.

Essence of Mobile IP

• Usage of old IP address but with a few additional mechanisms, to provide mobility

support

• MN assigned another Care of Address (COA)

Mobile IP

• Two types of COA

• Foreign Agent Based COA

COA of the MN is address of FA.

• Colocated COA– IP address belonging to the home sub-net.– A topologically correct IP

Mobile IP

Mobile IP

• Both methods use IP Tunneling

• Packet encapsulated at HA.

• The place of de- capsulation is difference in two methods.

• High degree of in-efficiency.

Asymmetric Routing

Registration with HA

• Initiated when MN moves to a new location.

• MN sends agent advertisement packet.

Involves authentication & authorization of MN by HA.

Advertising packet

Practical Constraints

• Ingress filtering

• Firewalls

• TTL

• Packets get blocked or dropped.

• Reduce TTL by only one till home.

• Follow triangular routing.

Simultaneous Binding

• More than one COA.

• HA needs to send duplicated packets to all

COA.

• Improves reliability of data transmission.

Route Optimization

• Make CN Mobility aware

• Ability to de - capsulate packets from MN

• Ability to send packets directly to MN

by passing HA.

Route Optimization

• Binding cache

Associating mobile node’s IP address with COA & lifetime is called binding.

This binding is done during registration.

Send this to CN.

Binding Cache Maintenance

• Four new UDP messages defined.

• Binding warning.

• Binding request.

• Binding update.

• Binding Acknowledgement.