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A Dynamical Redirection Approach to Enhancing
Mobile IP with Fault Tolerance in Cellular Systems
Jenn-Wei Lin, Jichiang Tsai , and Chin-Yu Huang
IEEE Global Telecommunication Conference 2002Taipei, Taiwan, R.O.C., Nov. 17-21, 2002
Department of Computer Science & Information Engineering, Fun Jen Catholic University, Taipei, Taiwan
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Outline
IntroductionIntroduction Background Proposed Approach Evaluation Conclusions
3
Introduction
Mobility IP in Cellular Systems– Ongoing data sessions without disruption due to
mobility
– IETF RFC 2002• Two kinds of mobility agents
– Foreign agent (FA)
– Home agent (HA)
– Failure Occurrence• Interrupting the data executable capability of mobile users
4
Introduction
Mobile Packet Data Flow – Data request
Radio Access Network
Mobile Mobile Packet Packet BaBackboneckbone
Foreign Agent Home Agent
Internet
Application Server
Mobile Node
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Introduction
Mobile Packet Data Flow – Data response
Home Agent
Internet
Application Server
Mobile Mobile Packet Packet BaBackboneckbone
Foreign AgentRadio Access Network
Mobile Node
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Introduction
Failure Occurrence – Failures in FAs
• Data requests unable to be delivered
Home AgentForeign Agent
Internet
Application Server
Failure
Radio Access Network
Mobile Node
Mobile Mobile Packet Packet BaBackboneckbone
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Introduction
Failure Occurrence– Failures in HAs
• Data response unable to be sent back
Home AgentForeign Agent
Internet
Application Server
Failure
Radio Access Network
Mobile Node
Mobile Mobile Packet Packet BaBackboneckbone
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Introduction
Goal– Not terminating the data services of mobile
users when failures occur in mobility agents• Proposing a reliable Mobile IP protocol in cellular
systems– Tolerating multiple failures of mobility agents
– Not needing the hardware support
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Outline
Introduction BackgroundBackground Proposed Approach Evaluation Conclusions
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Background
Wireless Network Model
RAN FA
FA
FA
Interconnection Network
MN
MN
RAN
RAN
Wireless IPBackbone
Router
Router
Router
Router
Router
Router
HA
HA
Internet
RAN: Radio Access NetworkFA: Foreign AgentHA: Home Agent
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Background
Previous Approaches– R. Ghosh and G. Varghese [1998]– J. H Ahn and C. S. Hwang [2001]– Features
• Mobility agent– Hardware replication
• Mobility information– Potential long registration delay– Stable storage
• Fault-tolerant range– Within a network segment
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Outline
Introduction Background Proposed ApproachProposed Approach Evaluation Conclusions
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Proposed Approach
Basic Idea– Workload redirection
• Network-initiated handoff– Redirecting the workload of the faulty FA to other failur
e-free FAs
• Tunneling – Redirecting the workloads of the faulty HA to other failu
re-free HAs
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Proposed Approach
Network-Initiated Handoff– Modifying the FA selection algorithm
• Relationship between RANs and FAs before a FA failure
FA
.
.
.
RAN
RAN
RAN
FA
FAInterconnection
Network
.
.
.
MN
MN
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Proposed Approach
Network-Initiated Handoff – Resetting the FA selection algorithm (Cont.)
• Relationship between RANs and FAs after a FA failure
Virtually moving the locations of MNs under the coverage area of the faulty FA
Faulty FA
.
.
.
RAN
RAN
RAN
Failure-free FA
Failure-free FAInterconnection
Network
.
.
.
MN
MN
: Original deliverypath
: Possibly fault-tolerantdelivery path
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Proposed Approach
Tunneling– Performing the tunneling on the neighbor route
rs
Wireless IPBackbone
HA
Internet
Router Router
Network Segment
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Proposed Approach
Tunneling– Intercepting the response packets by failure-fre
e HAs
Server
Wireless IPBackbone
Faulty HA
FA
Failure-free HA
Router
Tunneling
Tunneling
MNRAN
: Original delivery path : Fault-tolerant delivery path
Internet
Tunneling
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Proposed Approach
Reconstructing mobility information– Sending a mobility-reconstruction message to e
ach FA– Filtering the visitor list to find the MNs original
ly managed by the faulty HA– Re-organizing each selected visitor entry as the
form of a mobility binding entry
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Outline
Introduction Background Proposed Approach EvaluationEvaluation Conclusions
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Evaluation
Performance Degradation on a Failure-Free Mobility Agent– Probability of blocking packet data in a failure-free mo
bility agent
– Packet data to a mobility agent • Poisson distribution
– Processing time of packet data in a mobility agent• Arbitrary distribution
– M/G/c/c queuing model
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Evaluation
Blocking Probability of a Failure-Free Mobility Agent– Erlang’s loss formula given from the M/G/c/c queuing
model
c
i
i
k
c
k
Blocking
i
Fw
c
Fw
P
0 !
!
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Evaluation
Traffic Parameters
Parameter Meaning Value
F Number of faulty mobility agents 1
c Number of resource units in a mobility agent
50 (100)
λ Arrival rate of data to a mobility agent
10, 25, 50, 100
μ Service rate of data in a mobility agent
1
wk Ratio for redirecting the workload of the faulty mobility agent to the failure-free mobility agent k
0.1 to 1.0
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Evaluation
Blocking Probability of a failure-free FA
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Evaluation
Blocking Probability of a failure-free HA
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Evaluation
Blocking Probability– When is not too large (e.g. 10 in FA and
10, 25 in HA), the blocking probability nearly approaches 0 regardless of the variance of wk.
– When is very large (e.g. 100), the blocking probability may be not large for the smaller wk.
– Four used traffic intensities are larger than the general traffic intensity in a commercial wireless system
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Outline
Introduction Background Proposed Approach Evaluation ConclusionsConclusions
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Conclusions
A New Approach to Tolerating Multiple Failures of Mobility Agents– Not incurring failure-free overhead– Not requiring hardware support– Dynamically generating the backups of faulty mobility
agents Overhead
– Performance degradation on a failure-free mobility agent
– M/G/c/c queuing model (Erlang’s loss formula)
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Conclusions
Comparisons
ComparingMetrics
ProposedApproach
Approach in Ghosh and Var
ghese [1998]
Approachin Ahn and Hwa
ng [2001]
Hardware support
No Yes Yes
RangeWhole system
networkIn a network
segmentIn a network
segment
Failure-free overhead
NoPotential long
registration
Message logging and checkpointin
g
Failure overhead
Network-initiated Handoff
TunnelingSearching
ARP executionARP execution
Restoration
