Mobile IP works and the advantages of it in wireless communication. In IP networks,

1. Mobile IP

2. Background
• With new applications developing at a rapid
pace, and advancements in Mobile
Computing technology, the number of users
replacing their desktop PCs with super-
portable laptops is on the up.

3. Topics covered
• Simple overview : Mobile IP
• Tunneling
• TCP Comparison
• Route Optimization
• Mobile IP in IPv6

4. Design Goals : Mobile IP
• Make size and frequency of routing updates
as small as possible.
• Software level : Simplicity in
implementation
• Allow mobile nodes to operate with on one
IP address, instead of a spool of addresses.

5. Terminology
• Mobile Node
• Home Address, Home Link, and Home
Agent.
• Care-of Address, Foreign Link, and Foreign
Agent.

6. Components : Mobile IP
• Agent Discovery : Provides information
about home and foreign agents to the
mobile node.
• Registration : Mobile node requests services
from its foreign agent.
• Mobile IP defines the rules for routing any
type of packet - unicast, multicast, and
broadcast.

7. Overview of Operation
• When a mobile host moves out of its home
site, it contacts the closest foreign agent.
• Registration takes place.
• Previous foreign(local) agent if any are
notified regarding the change.
• Communication starts. (also known as
triangle routing).

8. Overview of Operation
Figure 1 :CN sending data to MN at home
Correspondent node
bulk data
acknowledgements
Home agent Foreign agent
bulk
adv
acknowledgements
Scenario A:
Mobile node No tunnelling
No fragmentation
No dogleg route

9. Overview of Operation
Figure 2:MN sending data to CN from home
Correspondent node
acknowledgements
bulk data
Home agent Foreign agent
acknowledgements
adv
Scenario B:
bulk
No tunnelling
Mobile node No fragmentation
No dogleg route

10. Overview of Operation
Figure 3:CN sending data to MN through Foreign Agent
Correspondent node
bulk data acknowledgements
tunnelled bulk data
Home agent Foreign agent
bulk data
Scenario C: adv
MTU is 1500 bytes acknowledgements
Tunnelling of bulk data
Fragmentation Mobile node
Dogleg route

11. Overview of Operation
Figure 4:MN sending data to CN via Foreign Agent
Correspondent node
acknowledgements bulk data
tunnelled acknowledgements
Foreign agent
Home agent
acknowledgements
Scenario D: adv
No tunnelling of data bulk data
Tunnelling of acks
No fragmentation Mobile node
Dogleg route

12. TCP Performance in Mobile-IP
• Factors affecting TCP performance
– Tunneling overhead
– Dogleg route overhead
– Fragmentation overhead
– Handover overhead

13. Scenario 1:
Correspondent node
bulk data
acknowledgements
Home agent Foreign agent
bulk
adv
acknowledgements
Scenario A:
Mobile node No tunnelling
No fragmentation
No dogleg route
Fig. 1 - Mobile node is receiving bulk data from the
correspondent node while the mobile node is at home. MTU
is 1500 bytes

14. Scenario 2:
Correspondent node
acknowledgements
bulk data
Home agent Foreign agent
acknowledgements
adv
Scenario B:
bulk
No tunnelling
Mobile node No fragmentation
No dogleg route
Fig. 2 - Mobile node is sending bulk data to the
correspondent node while the mobile node is at home. MTU
is 1500 bytes

15. Scenario 3:
Correspondent node
bulk data acknowledgements
tunnelled bulk data
Home agent Foreign agent
bulk data
Scenario C: adv
MTU is 1500 bytes acknowledgements
Tunnelling of bulk data
Fragmentation Mobile node
Dogleg route
Fig. 3 - Mobile node is receiving bulk data from the
correspondent node while the mobile node is at a foreign
network. MTU is 1500 bytes

16. Scenario 4:
Correspondent node
acknowledgements bulk data
tunnelled acknowledgements
Foreign agent
Home agent
acknowledgements
Scenario D: adv
No tunnelling of data bulk data
Tunnelling of acks
No fragmentation Mobile node
Dogleg route
Fig. 4 - Mobile node is sending bulk data to the
correspondent node while the mobile node is at a foreign
network. MTU is 1500 bytes

17. Scenario 5:
Correspondent node
bulk data acknowledgements
tunnelled bulk data
Home agent Foreign agent
bulk data
adv
acknowledgements
Scenario E:
MTU is 1450 bytes Mobile node
Tunnelling of bulk data
No fragmentation
Dogleg route
Fig. 5 - Mobile node is receiving bulk data from the
correspondent node while the mobile node is at a foreign
network. MTU is 1450 bytes

18. Comparisons: Differences in Setup
Scenario : Sender of the Location of MTU (in
file mobile node bytes)
A CN At home 1500
B MN At home 1500
C CN At foreign 1500
D MN At foreign 1500
E CN At foreign 1450
Table 1 - Differences in setup between the five different scenario

19. Comparisons: Presence of tunneling, fragmentation
and dogleg route
Scenario : Tunnelling Fragmentation Dogleg route
overhead overhead overhead
present? present? present?
A No No No
B No No No
C Yes Yes Yes
D Yes No No
E Yes No Yes

20. Test Details
• MTU in scenario 5 was reduced solely to
prevent fragmentation.
• Comparison using FTP file transfer, 30.2
MB file ≈ 241.6 Mbits
• Repeated 20 times
• Throughput = file size / mean transfer time
• % throughput = throughput / maximum
capacity of link

21. Comparisons: Mean transfer time and standard
deviation for FTP file transfer
Scenario : Mean transfer Standard Throughput
time (s) deviation (s) (Mbit/s)
A 41.21 1.81 5.86
B 43.30 1.04 5.58
C 78.22 1.43 3.09
D 46.17 1.14 5.23
E 75.62 1.33 3.19

22. Evaluations
• File transfer takes 90% more time to complete, with all 3
overheads.
• Encapsulation and Decapsulation of bulk data or
acknowledgments takes the same time
• The longer route results in a higher delay before the
packets reach the mobile node
• Link usage will increase if the IP packet and its
encapsulated form both use the same link while being
routed to the destination
• The tunneling overhead causes the file transfer to take
about 7% more time to complete

23. Evaluations
• Fragmentation overhead causes the file transfer to take
about 6% more time to complete
• The dogleg route overhead obtained using this method
causes the file transfer to take about 80% more time to
complete
• The handover overhead will depend on the TCP handover
latency, the frequency of handoffs, the duration of the TCP
connection and the agent advertisement interval
• The TCP handover latency is about 60% more than the
MIP network handover latency

24. Evaluations
• The handover overhead is about 13%.
• Two ways of reducing the handover overhead:
– reduce the retransmission timer value
– reduce the agent advertisement interval.
• Tradeoff: bandwidth consumption

25. Route Optimization and
Authentication
• The paper describes the Internet Mobile
Host Protocol with the following features:
– route optimization
– authentication of management packets
– performance and operational
transparency to the user.

26. IMHP Architecture Entities
• Mobile host
– unique home address
• Local Agent
– helps mobile host register, provides care-
off address
– maintains a visitor list
• lists all the mobile hosts
• needs to be refreshed

27. IMHP Architecture Entities
• Cache Agent
– Maintains the location cache
– using cache entry the data packet is
“tunneled” to the mobile host.
• Done by including a small IMHP header
• adds 8 or 12 bytes of overhead to each
packet

28. IMHP Architecture Entities
• Home Agent
– maintains a home list
– special case: home agent maintains a
visitor entry for mobile host
– must also be a cache agent for its mobile
hosts

29. Authentication
• Basically required to authenticate
binding and management packets.
• MH to HA : by including an
authenticator based on a shared secret
• General Authentication: node sends a
request for binding with random
number and gets reply with the same
number.

30. Authentication
• Use of route flag in management packet to
enforce normal IP routing of packet.
• Local agent authenticates visitor list entries
from the home agent.
• All entries into lists are timer based.

31. Optimization
• special tunnel packet - destination of
tunnel is same as destination of packet.
• Specified as a set of forwarding rules
for the IMHP entities.

32. Rules for forwarding
• Node receives tunneled packet with its
own destination address.
• Node receives a non-tunneled packet
with its own destination address

33. Rules: Home Agent
• HA receives an IMHP management
packet with route flag set.
• HA receives a special tunnel packet.
• HA receives packet for one of its
mobile hosts
– HA has a visitor entry for the host.
– HA does not have a visitor entry.

34. Rules: Home Agent
• HA never tunnels a packet back to a
node that has just tunneled the packet
to it.

35. Rules: Other Agents
• Receives special tunnel packet with route
flag set.
• LA receives a tunneled packet for host in
visitor list.
• LA receives a regular packet for host in
visitor list
• CA receives a packet and has an entry in its
location cache.

36. Rules: Other Agents
• Receives packet that was tunneled directly
to this node, and the agent is unable to
forward it further.
– Solution : special tunnel

37. Bindings
• Binding notifications:
– MH notifies HA and previous LA about
“change of address”.
– Any node can notify any other node
about wrong binding information stored
by it.
– Notification Back-off

38. IMHP : Other Issues
• restrictions on advertising bindings - use of
private flag.
• MH in Popup Mode
– requires facilities such as DHCP
– acts as its own local agent.
– Binding should be kept private
• Performance of MH at home should be like
a stationary host.

39. Mobility Support in IPv6
• IPv6:
– 128 bit address space
– link local addresses
• Extension headers : Destination
Options header, hop-by-hop header,
routing header and an authentication
header.

40. Overview of Mobile IPv6
• All packets carrying information must be
authenticated.
• Avoid “remote redirection” attacks
• Allows MH to allow more than one care-of
addresses at a time, but registers only one of
its bindings.
• Allows CH to dynamically learn the MH’s
binding. In this case it uses the Routing
header but does not encapsulate.

41. Overview of Mobile IPv6
• Reasonable to expect all the IPv6 nodes to
have caching capabilities.
• Implementation of the Binding Updates and
Binding Acknowledgments - the key to
reliability and optimization.

42. Binding Update Option
• Provides optimization and performance in
IPv6
• Used by mobile host to:
– notify home agent of its primary care-of
address
– notify correspondent nodes of its current
binding
• Binding Updates should always be
authenticated.

43. Binding Update Format

44. Binding Update Format
• Lifetime:time duration for which the
binding remains valid.
• Identification: To ensure in order
processing of updates.
• Care-of address: Holds the current care of
address

45. Binding Update Format
• Flags:
– H: Destination requested to serve as home
agent.
– A: Acknowledgment expected
– L:Link Local address present
• Updates could be retransmitted if there is no
acknowledgment.

46. Binding Acknowledgment Format

47. Binding Acknowledgment Format
• Code: indicates whether binding update
was accepted or rejected.
– < 128 update accepted
– >= 128 update rejected
• Lifetime: during for which node will retain
the binding.
• Refresh: time interval for sending updates
• Identification: Same number as the update.

48. Sending Updates
• First update sent to home agent to register
the new care-of address.
– From another foreign network
– From the home network
• Can be included in a regular packet or sent
alone.
• Only the mobile node can send its own
binding updates.

49. Movement detection
• Neighbor Discovery protocol including
Router Discovery and Neighbor
Unreachability Detection to create list
• Selects the default router from the list
• configures its care-off address

50. Unreachability
• detecting unreachability
– using the Neighbor Unreachability detection
– using the higher layers
– using the lower layers.
– When not receiving packets

51. Smooth Handoffs
• Using overlapping cells - accept packets at
multiple addresses for a short while.
• Router Assisted - Previous router can
forward packets to new local router.
• Renumbering the home network

52. CH & HA Operations
• Sending packet to MH
• Handling ICMP error messages
• Home agent discovery

53. More information on Mobile IP
• National University of Singapore
• Carnegie Mellon University
• Columbia University

54. • Presentation based on the reading
list sent out earlier.
All diagrams and tables have been included
from the reading list research papers.

55. Mobile IP
Prashant Bhargava
CS 599 : Wireless Communications
and Mobile Computing
602 08 8857