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Mobile IP. Overview: Standard IP Evolution of Mobile IP How it works Problems Assoc. with it. What is an IP?. A computer’s return address. Each computer on the network has a unique set of numbers (0-255) in the form of XXX.XXX.XXX.XXX Can be static or dynamic.

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Mobile ip

Mobile IP


Standard IP

Evolution of Mobile IP

How it works

Problems Assoc. with it

What is an ip
What is an IP?

  • A computer’s return address.

  • Each computer on the network has a unique set of numbers (0-255) in the form of XXX.XXX.XXX.XXX

  • Can be static or dynamic.

  • IP addresses enable IP routing algorithms to get packets to the correct network

Evolution of mobile ip
Evolution of Mobile IP

In standard IP, end hosts are in fixed physical locations. So, if a host moves to another physical location, it has to change its IP address

Mobile IP allows hosts to stay connected to the internet regardless of their location.

Mobile ip1
Mobile IP

  • Mobile IP was created to allow users to KEEP THE SAME IP ADDRESS while ‘traveling’ to a different network (which may even be on a different wireless operator), This means that roaming individuals can continue communication without breaking their connection.

What makes it possible
What makes it possible?

The three components of Mobile IP: *Mobile Node (MN)

*Home Agent (HA) *Foreign Agent (FA)

Home & Foreign Agents are also known as Mobile Agents

Mobile ip components relationship
Mobile IP Components & Relationship

How does it work 1 3
How does it work? (1/3)

Each mobile node has two IP addresses:

  • A permanent home address that is assigned to the home network and;

  • A temporary care-of address representing the current location of the host.

    Mobility is supported by transparently binding the home address of the mobile node with its care-of address.

How does it work 2 3
How does it work (2/3)

Mobility binding is maintained by specialized routers known as mobility agents.

Table mapping a mobile node's home address with its care-of address.

Mobility Binding Table

How does it work 3 3
How does it work? (3/3)

Foreign Agents are specialized routers on the foreign network where the mobile node is currently visiting.

The FA maintains a visitor list which contains information about the mobile nodes currently visiting that network.

Visitor List

Mobile ip protocol 1 5
Mobile IP Protocol (1/5)

STAGE 1: Agent Discovery

Mobility agents periodically broadcasts Agent Advertisement messages.

With this AA, a mobile node determines if it is on the home or foreign network.If a mobile node discovers that it is on the home network operate without mobility services. If it discovers it’s on a new network…….

Mobile ip protocol 2 5
Mobile IP Protocol (2/5)

STAGE 2: Registration

Mobile node registers with the foreign agent by sending a Registration Request message.

Foreign agent registers on behalf of the mobile host by sending a RR to the home agent.

Home agent receiving RR updates MBT.

Acknowledgement sent to Foreign Agent, which updates its visitor list and relays reply to Mobile Node.

Mobile ip protocol 4 5
Mobile IP Protocol (4/5)

STAGE 3: In-Service

When a correspondent node communicates with the mobile node, it sends an IP packet addressed to the permanent IP address of the mobile node.

The home agent intercepts this packet and consults the MBT to verify that the mobile node is currently visiting another network.

HA obtains the MN care-of address and constructs a new IP header containing MN’s care-of address as the destination IP address.

The original IP packet is put into the payload of this IP packet and is sent. Encapsulating an IP packet into the payload of another is known tunneling.

Mobile ip protocol 5 5
Mobile IP Protocol (5/5)

When encapsulated packet reaches the mobile node's current network, the FA decapsulates the packet and finds mobile node's home address.

It then consults the visitor list to see if it has an entry for that mobile node.

If an entry exists, the foreign agent retrieves the corresponding media address and relays it to the mobile node.

When a mobile node wants to send a message to a correspondent node, it forwards the packet to the FA, which in turn relays the packet to the correspondent node using normal IP routing.

Shortcomings of mobile ip
Shortcomings of Mobile IP

  • Triangle Routing - when the correspondent host and the mobile host are in the same network, the messages will experience unnecessary delay since they have to be first routed to the home agent that resides in the home network

Other problems
Other Problems

  • Security – Firewalls often makes it hard for Mobile IP because they block all classes of incoming packets that do not meet specified criteria.

  • Competition from other protocols - other alternative protocols also offer portability to mobile computers. (E.g PPTP, L2TP)

  • Slow Growth in wireless LAN?


Cisco Mobile IP solutions

Association for Computing Machinery

Mobile Networking Through Mobile IP

Charles E Perkins, Sun Microsystems