1

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

jwlin@csie.fju.edu.tw

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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

5

Introduction

Mobile Packet Data Flow – Data response

Home Agent

Internet

Application Server

Mobile Mobile Packet Packet BaBackboneckbone

Foreign AgentRadio Access Network

Mobile Node

6

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

8

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

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Thank You for Your Attention

Jenn-Wei Lin

jwlin@csie.fju.edu.tw