Introduction to Mobile IP topics like location and handoff management, Mobile IP, Mobile IP in IPv6, and security.

1. Mobile IP
CS4492 Wireless and Broadband Networking
Dilum Bandara
Dilum.Bandara@uom.lk

2. Outline
 Location management
 Handoff management
 Mobile IP
 Mobile IP in IPv6
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3. Why?
 Everything is becoming mobile
 IP wasn’t designed with mobility in mind
 Goals
 Users
 Transparent roaming
 Software level
 Simplicity in implementation
 Network level
 Minimum routing updates & low overhead
 Allow nodes to operate with on one IP address, instead of a
spool of addresses 3

4. Mobility Management – Tasks
 Location management
 Establishing connections to MN
 Search & update
 Search cost vs. update cost
 Granularity vs. search cost
 Handoff management
 Maintaining network connectivity
 Routing packets/connection
 Deciding when to handoff
 Selecting new AP
 Acquiring resources such as channels
 Informing old AP 4

5. Location Management
 Location Registers (LR)
 Location management using a single LR
 Home Location Register (HLR)
 HLR maintains mobility binding
 Last known cell for each mobile node
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6. Location Management Using a Single
LR
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Source: Adelstein et al., Fundamentals of Mobile and
Pervasive Computing, Tata McGraw-Hill, 2005

7. Location Management Using a Single
LR (Cont.)
7
Source: Adelstein et al., Fundamentals of Mobile and
Pervasive Computing, Tata McGraw-Hill, 2005

8. Location Management Using a Single
LR (Cont.)
8
Source: Adelstein et al., Fundamentals of Mobile and
Pervasive Computing, Tata McGraw-Hill, 2005

9. Location Management Using a Single
LR (Cont.)
9
Source: Adelstein et al., Fundamentals of Mobile and
Pervasive Computing, Tata McGraw-Hill, 2005

10. Location Management (Cont.)
 Single HLR
 Single point of failure
 Single bottleneck
 Distributed HLR
 How to distribute location information?
 Degree of replication?
 Registration Area (RA) based location management
 One LR for one RA
 Organization of location registers?
 Flat or hierarchical
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11. RA-Based Location Management
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Source: Adelstein et al., Fundamentals of Mobile and
Pervasive Computing, Tata McGraw-Hill, 2005

12. Deciding When to Handoff
 Factors to consider
 Signal strength &
quality
 Load on current AP/
base station
 Availability of resources
in AP / base station
 Mobility patterns
 MN controlled vs.
network controlled
 Soft handoff vs. hard
handoff 12
Source: http://telecommunicationengineeringconcepts.
blogspot.com/2012/05/gsm-handoverhandoff.html

13. Location Management In GSM
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Source: www.freepatentsonline.com/7171219.html
• A separate VLR is maintained for each RA

14. Mobile IP
 Developed to transparently deal with problems of mobile
users
 Enables hosts to stay connected to Internet
regardless of their location
 Enables hosts to be tracked without needing to
change their IP address
 Requires no changes to software of non-mobile
hosts/routers
 Requires addition of some infrastructure
 Requires no modifications to IP addresses or IP
address format
 Supports security
14

15. Mobile IP Operation – Extensions to
IPv4
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Source: http://searchunifiedcommunications.techtarget.com/feature/Mobile-IP-networks-An-overview

16. Terminology
 Mobile Node (MN)
 Home Address
 Permanent address assigned to MN
 Home Agent (HA)
 Router located on home network of MN
 Does mobility binding of MN’s IP with its COA
 Forwards packets to appropriate network when MN is away
 Care-of Address (CoA)
 Address which identifies MN’s current location
 Sent by FA to HA when MN attaches
 Foreign Agent (FA)
 Router that is used to send/receive data to/from HA
 Forward’s MN’s registration request 16

17. Protocols Operation
 Agent Discovery
 Registration
 Data Transfer
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18. Agent Discovery & Registration
 HA’s & FA’s broadcast their presence to network
they are attached
 Beacon messages via ICMP Router Discovery
Protocol (IRDP)
 MN’s listen for advertisement & then initiate
registration
 When MN is away, it registers its COA with its HA
 Typically through the FA with strongest signal
 Registration control messages are sent via UDP to a
well-known port
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19. Registration Process
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20. Agent Discovery & Registration
(Cont.)
 After receiving registration request from a MN,
HA acknowledges & registration is complete
 HA intercepts all packets destined for MN
 HA masquerades as MN
 There is a specific lifetime for service before a MN
must re-register
 There is also a de-registration process with HA if MN
returns home
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HA FA

21. Tunneling
 When MN is in a different network
 HA encapsulates all packets addressed to MN &
forwards them to FA
 IP tunneling
 FA decapsulates all packets addressed to MN &
forwards them via hardware address
 Learned as part of registration process
 MN can perform FA functions if it acquires an (public) IP
address, e.g., via DHCP
 Bidirectional communications require tunneling
in each direction
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22. Mobile IP Tunneling
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23. Problems with Mobile IP
 “Triangle” routing
 What if MN is in same sub-network as the node to
which it is communicating & HA is on other side of the
world?
 It would be nice if we could directly route packets
 Solution – Let Correspondent Node (CN) know COA
of MN
 Then CN can create its own tunnel to MN
 CN must be equipped with software to enable it to learn COA
 Initiated by HA who notifies CN via “binding update”
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24. Triangular Routing Problem
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25. Problems with Mobile IP (Cont.)
 Single HA model is fragile
 Solution – have multiple HA
 Frequent reports to HA if MN is moving
 Possible solution – support of FA clustering
 Security
 Connection hijacking, snooping…
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26. Security in Mobile IP
 Authentication can be performed by all parties
 Only authentication between MN & HA is required
 Keyed MD5 is the default
 Replay protection
 Timestamps are mandatory
 Random numbers on request reply packets are
optional
 HA & FA don’t have to share any security
information
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27. Mobility in IPv6
 Route optimization is a fundamental part of
Mobile IPv6
 Mobile IPv4 is an optional set of extensions that may
not be supported by all nodes
 FAs aren’t required in Mobile IPv6
 MNs can function in any location without services of
any special router in that location
 No tunneling
 Mobility Header – IPv6 extension header
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28. IPv6 Extension Header
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29. Mobility in IPv6 (Cont.)
 Route optimization provided to avoid “triangular
routing” problem
 Return routability procedure to secure binding
updates
 Fast handover
 Use hierarchical mobile IP
 Security
 Nodes are expected to employ strong authentication
& encryption
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30. Secure Binding Updates for
Corresponding Nodes
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31. Proxy Mobile IPv6 (PMIP)
 Network-based
mobility management
for hosts
 Host changes point-
of-attachment without
changing its IP
address
 Network is
responsible for
mobility management
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MAG – Mobile Access Gateway
Source: www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_13-3/133_pmipv6.html