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Mobile IP
IP
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?
Cellular Network
Addressing
The IP addresses are designed to work
with stationary hosts because part
of the address defines the network to
which the host is attached.
Mobile IP
Addressing
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.
13.10.121.11/16
182.12.11.78/24
Internet
182.12.11.0/24
13.10.0.0/16
Care of address: Mobile host original home address.
Mobile IP
Mobile IP
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.
Addressing
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.
Mobile IP
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
How these addresses are converted into each other?
Who will handle these addressing to provide communication services without
interruption?
Mobile IP
Agent
Agent provide transparent change in address.
Home Agent.
Foreign Agent.
Mobile IP
Home Agent & Foreign Agent
Mobile IP
Communication
• Example network
HA
MN
router
home network
Internet
(physical home network
for the MN)
FA
foreign
network
router
(current physical network
for the MN)
CN
end-system
router
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Communication
• Data transfer to the mobile system
HA
2
MN
home network
Internet
receiver
3
FA
1
CN
sender
foreign
network
1. Sender sends to the IP address of MN,
HA intercepts packet
2. HA tunnels packet to COA, here FA,
by encapsulation
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3. FA forwards the packet to the MN
Communication
• Data transfer from the mobile system
HA
1
home network
MN
sender
Internet
FA
foreign
network
1. Sender sends to the IP address
of the receiver as usual,
FA works as default router
CN
receiver
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Mobile host to Remote host communication
To communicate with remote host, mobile host requires three phases.
1. Agent Solicitation
2. Registration
3. Data Transfer
Mobile IP
Mobile host to Remote host communication
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Mobile IP
Mobile host to Remote host communication
Agent Advertisement
HA and FA periodically send advertisement messages into their physical subnets
MN 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
Advertisement
HA advertises the IP address of the MN (as for fixed systems), i.e. standard
routing information
Routers 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
Remote host to mobile host communication
1
2
3
Mobile IP
Inefficiency in Mobile IP-Double Crossing
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
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2
3
Sender sends all packets via HA to MN higher latency and network load
Solutions – optimization HA informs a sender about the location of MN . Sender
learns the current location of MN
direct tunneling to this location
big security problems!
Mobile IP
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?