Mobile IP - A layer upon normal IP to add mobility services

1. ACN Seminar
Mobile IP
NIJO JOB
CS-B S7
54

2. Mobile IP
- Mobile IP is a standard that allows users to move from one network
to another without loosing connectivity.
- It is a modification to IP that allows nodes to continue to receive
datagrams no matter where they happen to be attached to the
Internet
- The network is updated with the new location every time the user
changes the computer's point of attachment to the Internet.
- Mobile IP basically adds mobility support to the Internet network
layer protocol IP.

3. Requirement
s Compactability:- A new standard cannot introduce changes for
applications or network protocols already in use. Mobile IP has to
remain compatible with all lower layers used for the standard, non-mobile,
IP. End-systems enhanced with a mobile IP implementation
should still be able to communicate with fixed systems without
mobile IP. Mobile IP has to ensure that users can still access all the
other servers and systems in the internet using the same address
format and routing mechanisms.

4. Requirement
s Transparency:- Mobility should remain ‘invisible’ for many higher
layer protocols and applications. Besides maybe noticing a lower
bandwidth and some interruption in service, higher layers should
continue to work even if the mobile computer has changed its point
of attachment to the network. Many of today’s applications have not
been designed for use in mobile environments, so the only effects of
mobility should be a higher delay and lower bandwidth. However,
there are some applications for which it is better to be ‘mobility
aware’. Examples are cost-based routing or video compression.

5. Requirement
s Scalability and efficiency:- Introducing a new mechanism to the
internet must not jeopardize its efficiency. Enhancing IP for mobility
must not generate too many new messages flooding the whole
network. Also, it is crucial for a mobile IP to be scalable over a large
number of participants in the whole internet, worldwide.
Security:- The minimum requirement is that of all the messages
related to the management of Mobile IP are authenticated. The IP
layer must be sure that if it forwards a packet to a mobile host that
this host receives the packet.

6. Terminologie
s Mobile node:- A mobile node is an end-system or router that can
change its point of attachment to the internet using mobile IP.
Home network:- The home network of a mobile device is the
network within which the device receives its identifying IP address.
Correspondent node:- At least one partner is needed for
communication. The CN can be a fixed or mobile node.
Home address:- The home address of a mobile device is the IP
address assigned to the device within its home network.
Foreign network:- A foreign network is the network in which a mobile
node is operating when away from its home network.

7. Terminologie
s Care-of address:- The care-of address of a mobile device is the
network-native IP address of the device when operating in a foreign
network.
Home agent:- A home agent is a router on a mobile node’s home
network which tunnels datagrams for delivery to the mobile node
when it is away from home. It maintains current location information
for the mobile node. It is used with one or more foreign agents.
Foreign agent:- A foreign agent is a router that stores information
about mobile nodes visiting its network. Foreign agents also
advertise care-of-addresses which are used by Mobile IP.

8. Agent
Discovery A mobile node discovers its foreign agents and home agents during
agent discovery.
In mobile IP, both a foreign agent and a home agent periodically
broadcast agent advertisement messages.
A mobile host must discover(learn the address of) a home agent
before it leaves the home agent.
A mobile host must also discover a foreign agent after it moved to a
foreign network.
It allows mobile nodes to discover foreign agents and get care-of
addresses, to know the services provided by the foreign agent and to
determine whether an agent is its home agent or a foreign agent

9. Agent Solicitation
When an mobile host has moved to a new network and has not
received agent advertisements,it can initiate an agent solicitation.
A mobile node can generate agent solicitation messages when it is
looking for a foreign agent.

10. Registration
When a mobile node receives a care-of address from a foreign
agent, its home agent needs to be informed.
The mobile node sends a registration request to its home agent
through the foreign agent who has provided the new care-of
address.
When the home agent receives the request, it updates its routing
table and sends a registration reply back to the foreign agent.

11. Tunnelling
The transfer of the packet from the home agent to the care-of
address is called tunnelling
The home agent is the source of the tunnel. The home agent inserts
a new tunnel header in front of the IP header of a packet addressed
to the mobile agent and received by the home agent
The tunnel header is the care-of IP address of the mobile node. The
old header is preserved as it was in the original packet.
The foreign agent is the receiver of the tunnel
When the foreign agent receives the tunnelled packet, it has to
delete the tunnel header to recover the original packet.
The foreign agent delivers the packet to the mobile node after
removing the tunnel header

12. Data Transfer
When a remote host wants to send a packet to the mobile host, it
uses its address as the source address and the home address of
the mobile host as the destination address .
After receiving the packet, the home agent sends the packet to the
foreign agent . The home agent encapsulates the whole IP packet
inside another IP packet using its address as the source and the
foreign agent’s as the destination address.
When the foreign agent receives the packet, it removes the original
packet. Since, the destination address is the home address of the
mobile host, the foreign agent consults a registry table to find the
CAO.

13. Sample network
(current physical network
•for the MN)
•13
•HA
•home network
•(physical home network
•for the MN)
•Internet
•router
•MN
•router
•FA foreign
•network
•CN
•end-system •router

14. •14
•Tunneling
Data transfer to the mobile system
•Internet
•home network
•foreign
•network
•FA
•HA
•MN
•receiver
•1
•2
•3
•CN
•sender
•1. Sender sends to the IP address of MN,
• HA intercepts packet
•2. HA tunnels packet to COA, here FA,
• by encapsulation
•3. FA forwards the packet to the MN

15. •15
•Tunneling
•1
•foreign
•network
Data transfer from the mobile system
•home network
•Internet
•HA
•MN
•sender
•receiver
•CN
•FA
•1. Sender sends to the IP address
• of the receiver as usual,
• FA works as default router

16. Optimization
An inefficient behavior of a non-optimized mobile IP is called
triangular routing. The triangle is made of the three segments, CN
to HA, HA to COA/MN, and MN back to CN.

17. Optimization
The current location of the MN is informed to CN. The CN can learn
the location by caching it in a binding cache which is a part of the
local routing table for the CN.
- Binding request: Any node that wants to know the current location
of an MN can send a binding request to the HA.
- Binding update: This message sent by the HA to CNs reveals the
current location of an MN.
- Binding acknowledgement: If requested, a node returns this
acknowledgement after receiving a binding update message.
- Binding warning: If a node decapsulates a packet for an MN, but it
is not the current FA for this MN, this node sends a binding warning.

18. Reverse Tunneling
The return path from the MN to the CN looks quite simple. The MN
can directly send its packets to the CN as in any other standard IP
situation. The destination address in the packets is that of CN.
Quite often firewalls only allow packets with topologically correct
addresses to pass. However, MN still sends packets with its fixed IP
address as source which is not topologically correct in a foreign
network. Firewalls often filter packets coming from outside
containing a source address from computers of the internal network.

19. Reverse Tunneling
•19
•Internet
•receiver
•FA
•HA
•MN
•home network
•sender
•foreign
•network
•3
•2
•1
•1. MN sends to FA
•2. FA tunnels packets to HA
• by encapsulation
•3. HA forwards the packet to the
• receiver (standard case)
•CN

20. THANK YOU