Unit 5 : Mobile Network Layer
Question: Definition of Mobile IP
 Mobile IP is an internet protocol
 It enable the Mobile Device (Smart Phone / Laptop) to stay connect
with network while moving (Traveling) from one place to other place.
Explain about the Assumptions and Quick Solutions for IP problem.
Assumptions
 Every Mobile device has a unique IP address.
 IP address is used to access the Internet.
 Mobile device cannot change its IP address itself.
 If a Mobile device user moves from home network to a new
location/network , then new IP address need to access the internet
connection.
Quick Solution
– Assign new IP address when enter into new location.
Increase problem in TCP because TCP IP layer.
Routers are built for fast forwarding but not for fast update of routing table.
Question: Discuss about the development Goal of Mobile IP and the
requirements for a mobile IP.
Development Goal of Mobile IP:
Mobile IP goal is to provide the ability to Mobile Device to stay connected to
the Internet irrespective of their location (Home Location / New Location).
Requirement Standards for a mobile IP:
There are several requirements for Mobile IP to make it as a standard.
Some of them are:
1. Compatibility
2. Transparency
3. Efficiency and scalability
4. Security
1.Compatibility
 Mobile IP should be Compatible with existing operating system and
routers.
2.Transparency
 Mobility should ‘invisible’ to higher layer.
 Mobile device keep their IP address after point of connection
changed.
3.Efficiency and Scalability
 It should support the large number of mobile users to connect the
world wide web.
 Only additional packet should be necessary between a mobile system
and a node in the network.
4. Security
 The minimum requirement is that of all the messages related to the
management of Mobile IP are authenticated.
Question: Explain about the Entities (Parts) of the Mobile IP.
Mobile IP consists of the following entities:
1. Mobile Node (MN)
Mobile Node is Mobile Device or System. It uses Mobile IP address for
Network Access.
2. Correspondent node (CN)
The Partner of the Mobile Device ie. Sender / Receiver.
3. Home network (HA)
Home network of the Mobile Device / System Node.
4. Home Address
 Home Address is the permanent IP address
 It is assigned by the Home Network to the mobile node.
5. Foreign network (FA):
The foreign network is the current network that Mobile Device visits ( ie.
Roaming / Away from Home network).
6. Home Agent (HA)
1. Home Agent (HA) is a router in Home Network of the Mobile Device.
2. It stores the permanent home address and current location of the
mobile device.
3. It receives the data from Caller Mobile Device (Correspondent Node)
and forward the received data to corresponding Mobile Device
(Receiver).
7. Foreign Agent (FA)
 Foreign Agent (FA) is a router in Foreign Network of the Mobile
Device during Roaming (ie. current visiting location of Mobile
Device).
 It forward the data from the Home Agent to the Mobile Node during
Roaming
8. Care-Of Address (COA)
 It is a secondary, temporary address used by a mobile node while it
is 'traveling” away from its home network ie. Roaming.
 Also, COA is a Current Address of Mobile Device during Roaming
(ie Travelling).
 COA uses Tunneling mechanism to deliver the data to Mobile Device.
9. Foreign agent COA
 Foreign agent COA located at the Foreign Agent (FA).
 It is the IP address of the Foreign Agent (FA).
Question: Explain about IP Packet Delivery in Mobile IP.
According to below image,
1. Correspondent node (CN ie. Sender Device) sends the data to Mobile
Node (MN). So CN is a Source Device. Then the internet forwards
the data send by CN to Home Agent Router (Router HA). Indicated
by Blue Line 1.
2. Home Agent’s Router forward the data which sent by CN to COA
which is located in the Foreign Agent (FA). Indicated by Blue Line
2.
3. COA uses the Tunneling (ie. Starting Point and Ending Point of
source and receiver ) to deliver the data to the Mobile Node which is
in Foreign Network. Indicated by Blue Line 3.
4. Reverse: Sender responds to the message Indicated by Red Line
4.
Figure: IP Packet Delivery
Agent Discovery:
1. First, Home Agent (HA) and Foreign Agent (FA) advertise their
presence by broadcasting their agent advertisement messages using
the ICMP router discovery protocol (IROP).
2. Secondly, The mobile node receives the agent advertisement
message
and determines whether it is in the home network or
foreign network.
3. In case, if
the Mobile Node does not receive any Agent
Advertisement, then the Mobile Node will send Agent Solicitations
message to inform the Agents.
Registration
In this step, Mobile Node registers its current location with the Home Agent
(HA) and Foreign Agent (FA).
i.
In this process, First Mobile Node (MN) send the Registration
Request (RREQ) with its current location information to Home Agent
(HA).
ii.
Then the Home Agent (HA) reply through the Registration Reply
(RREP) message to Mobile Node (MN).
image).
Figure : Registration
(Please see the below
Tunneling
 Tunneling process is used to transfer the data to Mobile Node.
 When a data arrives at Home Agent (HA) for the mobile node, then
Home Agent (HA) forwards the data to the COA of Mobile Node using
a tunnel.
 Tunnel contains Entry Point and End Point. In Tunnel Entry Point is
Home Agent (HA) and End Point is COA in Foreign Agent (FA).
 Tunneling is done using Encapsulation. Encapsulation means putting
a packet header and data as data of another packet.
Explain about Dynamic Host Configuration Protocol (DHCP).
DHCP is a network management protocol.
DHCP automatically assigns a unique IP address to each device that
connects to a network.
DHCP is based on a client/server model as shown below.
Figure : Host Configuration Protocol (DHCP) Process
Figure : Host Configuration Protocol (DHCP) Process
Step 1: Client system send a DHCPDISCOVER request to a server for
configuration process.
Step 2: Servers System reply the client system and provides the
configuration parameters through DHCPOFFER reply.
Step 3: The Client system reply its Acceptance / Rejection through the
DHCPREQUEST reply to Server System.
Explain about Traditional TCP
TCP (Transmission Control Protocol) is used to connects the fixed
systems.
The major responsibilities of Transmission Control Protocol are:
1. Provide reliable Transport of data and Do not allow any data loss.
2. Congestion Control is the one of the major task TCP. Congestions
means Heavy Traffic in Network.
3. Control the data packet flow between the Transmitter and the Receiver.
Explain about the TCP Congestion Control.
Congestions means Heavy Traffic in Network.
 Congestions occurs when the Router’s Buffer is full. Due to this
problem the data packet may be lost.
 TCP protocol recognizes this Congestion problem through the
Missing Acknowledgement Notice and Re-Transmissions of data in
the sender side.
 If Congestion problem is detected, then the TCP protocol uses below
Two Algorithms to control the Congestion.
1. Slow Start algorithm
2. Fast Retransmit / Fast Recovery
1. Slow Start Algorithm:
i.
In slow start algorithm, TCP uses Congestion Window to control
the congestion problem.
ii.
The Congestion Window indicates the maximum amount of data
can be send to Receiver with out any congestion problem.
iii.
The sender device calculates the Congestion window for Receiver
Device. The initial size of the window is one segment.
iv.
The size of the Congestion Window increases exponentially until
it reaches the Congestion Threshold (Maximum Size) and then it
will linearly increase.
v.
If Congestion occurs, then sender resets the congestion threshold
size into half of the current congestion window size.
Congestion Threshold Size = Half of the current Congestion Window Size.
In this way congestion is control by slow start algorithm.
vi.
So the send data size will be decreased and congestion is controlled.
2. Fast Retransmit / Fast Recovery Method:
 If the packet loss occurs, then TCP uses Fast Retransmit / fast
recovery mechanism.
 The sender performs the Fast retransmit /Fast Recovery process.
 In Fast retransmit /Fast Recovery process, the sender retransmits
the lost packets to the receiver.
 In this way, TCP controls the data losses between the Sender and
Receiver.
Explain about Mobile IP Security.
Mobile IP is developed based on the IP protocol for the internet access. So
Mobile IP and IP will expects the same security problem.
SECURITY of Mobile IP is improved by using the following Security Methods:
1. Using Tunneling Instead Of Source Routing:- Tunneling
mechanism is secured way to transfer the data. ie. Tunneling is more
secured than the Source Routing Method.
2. IPSec (Internet Security protocol) : IPSec is a Internet Security
protocol. IPsec is developed by IETF to protect the private network
communications using cryptographic security services.
3. Firewall : The Firewall is used to prevent unwanted access to
network services.
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