Fault-Tolerant Design

for Mobile IPv6 Networks

Jenn-Wei Lin and Ming-Feng Yang

Graduate Institute of Applied Science and EngineeringFu Jen Catholic University

22

Outline

Introduction

The Proposed Approach

Simulation

Conclusion

References

33

Introduction

Mobile IPv6 Operation

AR AR

HA

CN

RegularIPv6 Router

RegularIPv6 Router

HomeNetwork

ForeignNetwork

Internet

Packets

MN

HA: Home Agent MN: Mobile Node CN: Correspondent Node AR: Access Router

44

Introduction

Mobile IPv6 Operation

AR AR

HA

CN

HomeNetwork

ForeignNetwork

Internet

1. Binding update

2. Binding acknowledgement

HA: Home Agent MN: Mobile Node CN: Correspondent Node AR: Access Router

RegularIPv6 Router

RegularIPv6 Router

Handoff

MN

55

Introduction

Mobile IPv6 Operation

AR AR

HA

CN

MN

HomeNetwork

ForeignNetwork

Internet

Packets

Tunnel packets

Triangle routing problem

Handoff

HA: Home Agent MN: Mobile Node CN: Correspondent Node AR: Access Router

RegularIPv6 Router

RegularIPv6 Router

66

Introduction

Mobile IPv6 Operation

AR

HA

CN

MN

HomeNetwork

Internet

1. Binding update

3. Binding acknowledgement

AR

ForeignNetwork

Handoff

HA: Home Agent MN: Mobile Node CN: Correspondent Node AR: Access Router

RegularIPv6 Router

RegularIPv6 Router

2. Cache the current location of the MN

Route optimization

4. Packets

77

Introduction

Motivation If a failure occurs in an HA

Its managing MNs (the failure-effected MNs) cannot perform

binding updates. If an CN sends a packet to the failure-effected MN but it does

not cache the binding information of this MN, the packet will b

e lost.

88

Introduction

Goal Propose an efficient approach to providing fault-tolerant

capability for Mobile IPv6 network. Can handle the lost packets at the faulty HA.

Not dependent on the TCP layer to avoid incurring long

recovery latency.

99

Introduction

Network Model

CN1

Backbone Network

MN

．．．

．．．

．．

．

MN: Mobile Node AR: Access Router HA: Home Agent IR: Interconnection Router

CN2

HA1 HA3

AR1 AR3

IR1

AR4AR2

HA2 HA4

MN

IR3

IR5

IR2 IR4

Network Domain 1 Network Domain 3

Network Domain 2 Network Domain 4

．．

．

Internet

CN: Correspondent Node

A wide-area mobile network → A number of network domains

HA: Provide the mobility support for its managing MNsAR: Assist the MNs to forward packets within a network domain.IR: Transmit packets from a network domain to another.

1010

Introduction

Failure Detection Detected by MN

MN performs a binding update to its serving HA, but it does not

receive a binding acknowledgement for a certain period of time.

Detected by CN If a packet to an MN is required to go through the faulty HA, the

sending CN will receive an ICMP destination unreachable

message.

1111

Outline

Introduction

The Proposed Approach

Simulation

Conclusion

References

1212

The Proposed Approach

Basic Idea Initially, each MN gets or updates its preferable external HA

s from its default HA. When an MN detects a failure in its default HA, assign a ne

w serving HA and retrieve lost packets.

Handoff

Assign a newserving HA

andretrieve lost packets

Failure detection

Failure detection

Handoff

Update the preferable

external HAs

Get the preferable

external HAsInitial

1313

Handoff

Assign a newserving HA

andretrieve lost packets

Failure detection

Failure detection

Handoff

Update the preferable

external HAs

Get the preferable

external HAsInitial

The Proposed Approach

Preferable External HAs

1414

The Proposed Approach

Preferable External HAs (Cont.) Initially, each HA stores the identities of other HAs based

on the order of their location distances with the HA. The network model of this paper is under a wide-area mobile net

work, not mobile Internet. The number of HAs, the distance relationship between an HA an

d others, and the addresses of all the HAs in the system can be

known whiling establishing the Mobile IPv6 network.

1515

The Proposed Approach

Preferable External HAs (Cont.) The preferable external HAs are the HAs located in the n

etwork domains having different distance with the locate

d network domain of the MN Each MN can get its preferable external HAs from its default HA

via the binding update message. The new located network domain of the MN can be inferred fro

m the MN’s care-of-address.

1616

MN

HA4

HA2

HA1

HA5

HA6

HA3

(3-hop distance)

(1-hop distance)

(1-hop distance)

(2-hop distance)

(1-hop distance)

Homenetwork domain

MN

HA4

(2-hop distance)

HA2

HA1

HA5

HA6

(1-hop distance)

(2-hop distance)

(1-hop distance)

HA3

(1-hop distance)

Homenetwork domain

The Proposed Approach

Preferable External HAs (Cont.)

Handoff

The initial preferable external HAs

HA3

HA5

HA2

HA6

HA1

The preferable external HAs after handoff

HA5

HA4

HA6

HA3

HA2

HA1

1717

Handoff

Assign a newserving HA

andretrieve lost packets

Failure detection

Failure detection

Handoff

Update the preferable

external HAs

Get the preferable

external HAsInitial

The Proposed Approach

Assign a New Serving HA

1818

The Proposed Approach

Assign a New Serving HA (Cont.)When an MN

detects a failurein its default HA

Select first (next) preferableexternal HA as new serving HA

Generate a uniqueexternal home address

Perform a binding updateto the first (next)

preferable external HA

Success

Perform a binding updatewith each communicating CN

Yes

No

In the faulty oroverloading status

Select the HA that is close tothe current location of the MN

( external home address, care-of-address)

Route optimization

1919

The Proposed Approach

Assign a New Serving HA (Cont.)

The suffix of the external home address← The MN’s MAC address

MN has aMAC address

The prefix of the external home address← The prefix of the selected external HA

The suffix of the external home address← Use the MD5 hash function to generate

Combine the prefix and the suffixof the external home address

Combine the prefix and the suffixof the external home address

unique

Yes

No

Yes

No

Generate a uniqueexternal home address

2020

Handoff

Assign a newserving HA

andretrieve lost packets

Failure detection

Failure detection

Handoff

Update the preferable

external HAs

Get the preferable

external HAsInitial

The Proposed Approach

Retrieve Lost Packets

2121

The Proposed Approach

Retrieve Lost Packets (Cont.) When an CN would like to send a packet to the failure-

effected MN but it has not the MN’s binding information

in its binding cache. The packet will be forwarded through the faulty HA, and then

lost.

2222

IR1CN1

Faulty

default HA1

Failure

MN1

2. Tracking the sending ICMP destination unreachable messages

The undeliverable packet list

Destination address

MN1

::

Source address

CN1

::

4. Storing the undeliverable packets

The undeliverable packet buffer

Destination address

MN1

::

Undeliverable packet

Packet1

::

The Proposed Approach

Retrieve Lost Packets (Cont.) Before a packet is intercepted by a HA, the packet is first

received by a corresponding IR. Therefore, CN will receive

an ICMP destination unreachable message from IR. Ask the IR to trace its sending ICMP destination unreachable

messages to form an undeliverable packet list. Ask the CN to store the undeliverable packets in its undeliverable

packet buffer .

1. Packet1

3. ICMP destination unreachable

2323

The Proposed Approach

Retrieve Lost Packets (Cont.) The recovery process of the undeliverable packets

IR1

Faulty

default HA1

Failure

IR2

New

serving HA2

CN1 CN2 CN3

MN 1.a. Binding update

1.b. Binding update

3. Binding error and

Undeliverable packet recovery

2.a. Binding acknowledgement

2.b. Finding the undeliverable packet destined to the MN

4. Solicited binding update

5. Updating the binding information of the MN and finding the undeliverable

packets destined to the MN

6. Re-sending theprevious undeliverable

packet destined to the MN

2424

Outline

Introduction

The Proposed Approach

Simulation

Conclusion

References

2525

Simulation

Overhead of Tolerating Faulty HA The information about preferable external HAs is attache

d on the binding acknowledgement message. The overhead of the extended binding acknowledgement

message :

The number of attached external HAsis based on the required fault-tolerant capability of the proposed approach.

Allowing 9 HAs to simultaneously fail in the system.

2626

0

0.2

0.4

0.6

0.8

1

0 5 10 20

Number of failure-effected MNs

Tota

l bin

ding

upd

ate

late

ncy

(se

cond

s) Redundancy-basedapproachProposed approach

Simulation

Overhead of Tolerating Faulty HA (Cont.) Each failure-effected MN can select its preferable external

HA as the new serving HA after its default HA fails. The binding update latency for failure-effected MNs :

The preferable external HA is close to the current location of the failure-effected MN.

The failure-effected MNs can simultaneously perform binding updates to different new serving HAs.

2727

Simulation

Overhead of Lost Packet Recovery The undeliverable packets will be retrieved when a

failure-effected MN performs a binding update. The space overheads are mainly determined by the binding

update interval. The space overhead introduced by the lost packet recovery :

0.00.51.01.52.02.53.0

2 4 6 8 10

Binding update interval (seconds)

Size

s of

the

unde

liver

able

pack

et li

st (K

byte

s)

The undeliverable packet list The undeliverable packet buffer

0102030405060

2 4 6 8 10

Binding update interval (seconds)Si

zes of

the

unde

liver

able

pack

et b

uffer

(Kby

tes)

2828

Outline

Introduction

The Proposed Approach

Simulation

Conclusion

References

2929

Conclusion

An Efficient Approach to Tolerating the HA Failure i

n a Mobile IPv6 Network System. Consider how to recover from the lost packets at the fault

y HA. The simulation results show that the incurred overhead is

very small. If The probability that many HAs simultaneously fail is small The binding update interval is not too long,

3030

References

3131

References

3232

Thank you for your listening.