An Agile Vertical Handoff Scheme for Heterogeneous Networks

An Agile Vertical Handoff Scheme for Heterogeneous Networks

Hsung-Pin Chang

Department of Computer Science

National Chung Hsing University

Taichung, Taiwan, R.O.C.

Outline Motivation Related work

How to achieve seamless vertical handoff ? Challenge and Contribution

How to pass NAT gateway ? How to adapt TCP behavior ?

Experiments Conclusion

Outline Motivation Related work

How to achieve seamless vertical handoff ? Challenge and Contribution



Hierarchical Overlay Network Many different communications systems

coexist around us Ethernet, Wireless LAN, GPRS, 3G…

Each owns different characteristics Bandwidth, delay, cost……

Hierarchical overlay network The combination of these heterogeneous

networks

Example: An Overlay Networks

Campus-wide (3G, GPRS)

Building-wide (WLAN)

Room-wide (Ethernet)

Horizontal versus Vertical Handoff Problem: handoffs

Horizontal handoff The same kind of network technology Ex: BSS to BSS

Vertical handoff Different kinds of network technologies Ex: Wireless LAN to 3G

<= what we are addressed

Horizontal Handoff

AP AP

BSSBSS

InternetInternet

Vertical Handoff

WCDMA

WLAN

APBS

InternetInternet

Outline Motivation Related work: how to achieve seamless

vertical handoff ? Challenge and Contribution



Previous Approaches to Vertical Handoff 1/2

Mobile IP/Infrastructure Based Approaches

Mobile IP with multicast Care-of-address is changed to a multicast address

Integration of WLAN and GPRS Integration of WLAN and 3G

Problem Require modification of network infrastructure

Hindrance to deployment Need to be keep up to data

New technologies are always introduced

Previous Approaches to Vertical Handoff 2/2

End-to-end based Application layer

SIP (Session Initiation Protocol)

Transport layer: enable TCP connection alive even the underlying IP address is changed TCP-R TCP Migrate

Between transport layer and network layer C. Guo, et. al., “A Seamless and Proactive End-to-End Mobility

Solution for Roaming Across Heterogeneous Wireless Networks,” IEEE JSAC, 22(5), pp.834-848. Jun. 2004

Network Applications

BSD Sockets

TCP UDP

User

KernelSocket Interface

Transport Layer

IP

PPP SLIP EthernetNetwork Devices

Network Layer

LCT Table Translation

A Seamless and Proactive End-to-End Solutions for Roaming Across Heterogeneous Wireless Networks (1/4)

Originaladdress

Original port

Mapped address

Mapped port

A p1 A p1

WLAN

LAN

LAN

Nego A BTell B that A support vertical handoff

Nego+AckBAB Tell A ok.

NotifyC B

A

AckBC

AB

C

Originaladdress

Original port

Mapped address

Mapped port

A p1 A p1

Mobile Client Fixed Host

…

Originaladdress

Original port

Mapped address

Mapped port

A p1 C p2

Originaladdress

Original port

Mapped address

Mapped port

A p1 C p2


Handoff LayerHandoff Layer

ApplicationApplication

Handoff LayerHandoff Layer

Kernel

ApplicationApplication

Kernel

A B A B

C B

Table LookupTable Lookup

圖 3 封包表頭替換過程



Problems NAT issue

Require an S/N (Subscription/Notification) Server Modify the infrastructure

TCP performance Do not consider





How to pass NAT gateway ? Problem

Communication must always be initiated by the private network

Solution Use the previous IP address as the source IP

address

WLAN

Fixed Host

Ethernet

NAT

AP

Switch

Update

New IP address

Problem

WLAN

Fixed Host

Ethernet

NAT

AP

Switch

Update

Old IP address

Solution

Outline Motivation Related work: how to achieve seamless vertical

handoff ? Challenge and Contribution

How to pass NAT gateway ? How to adapt TCP behavior ? => CWND-Restore


How to adapt TCP behavior ? Problem

TCP consider packet loss as network congestion Slow down…

But…now packet lose is because “handoff”

Solution CWND-Restore

WLAN

Fixed Host

Ethernet

NAT

AP

Switch

CWND-RestoreCWND 20CWND 2CWND 50





System Implementation- Linux Kernel 2.6.11

EthernetDriver

EthernetDriver

WLANDriver

WLANDriver

3G3G

ApplicationsApplications

Connection ManagerConnection Manager

TCPTCP

User Mode

Kernel Mode

UDPUDP

IPIP

Handoff DetectionHandoff Detection

CWND-restoreCWND-restore

Experimental Platform

Fixed Host Mobile Host

CPU AMD XP 2600+ Intel Pentium M 1.4GHz

RAM 512 MB 256 MB

NIC #1 100Mbps Ethernet100Mbps Fast Ethernet Ethernet

NIC #2Philips 802.11g WLAN miniPCI Adapter

NIC #3Novatel UMTS/WCDMA USB Adapter

Experiment 2/2

Experiments TCP handoff verification

Handoff latency

TCP handoff performance

UDP handoff verification

Experiment 2/2


Handoff latency



TCP Handoff Verification 1/7

InternetInternet

Ethernet

WCDMAFixed Host

Mobile Host

WLAN

NAT

NATBS

B A

C

AP

Switch

Experiment environment


LAN to WLAN

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

0 1 2 3 4 5 6 7 8 9 10

Se

que

nce

Num

ber

(K

B)

Time (sec)

"LAN""WLAN"

Handoff


WLAN to LAN

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

3 3.5 4 4.5 5

Se

que

nce

Num

ber

(KB

)

Time (sec)

"LAN""WLAN"

Handoff


LAN to WCDMA

0

1000

2000

3000

4000

5000

6000

0 50 100 150 200

Se

que

nce

Num

ber

(K

B)

Time (sec)

"LAN""WCDMA"

Handoff


WCDMA to LAN

0

1000

2000

3000

4000

5000

6000

0 50 100 150 200 250

Se

qu

en

ce N

um

be

r (K

B)

Time (sec)

"LAN""WCDMA"

Handoff


WLAN to WCDMA

0

1000

2000

3000

4000

5000

6000

0 50 100 150 200 250

Se

que

nce

Num

ber

(K

B)

Time (sec)

"WLAN""WCDMA"

Handoff


WCDMA to WLAN

0

1000

2000

3000

4000

5000

6000

0 50 100 150 200 250

Se

que

nce

Num

ber

(K

B)

Time (sec)

"WLAN""WCDMA"

Handoff

Experiment 2/2


Handoff latency



Handoff Latency 1/2

WCDMA

InternetInternet

WLAN

Fixed Host

Mobile Host

Ethernet

NAT

AP

Switch

BS

B

A C


Handoff Latency 2/2

Handoff Latency (ms)

LAN to WLAN 3

LAN to WCDMA 438

WLAN to LAN 1

WLAN to WCDMA 503

WCDMA to LAN 1

WCDMA to WLAN 3

Experiment 2/2


Handoff latency



TCP Handoff Performance 1/8

WCDMA

InternetInternet

WLAN

Fixed Host

Mobile Host

Ethernet

NAT

AP

Switch

BS

B

A C


TCP Handoff Performance 2/8

Original (KB/s) CWND Freeze (KB/s)

WLAN to LAN 6154.8 7690.84

LAN to WLAN 177.58 244.87

WCDMA to LAN 2886.36 5059.62

WCDMA to WLAN 138.34 237.77

LAN to WCDMA 3.64 3.98

WLAN to WCDMA 3.47 4.12

TCP handoff performance 3/8

LAN to WLAN

0

10

20

30

40

50

60

70

80

90

100

9 9.5 10 10.5 11

Con

gest

ion

Win

dow

s

Time (sec)

"Original""CWND Freeze"

Handoff


WLAN to LAN

0

10

20

30

40

50

60

70

80

90

100

9 9.5 10 10.5 11

Con

ges

tion

Win

dow

s

Time (sec)


Handoff


LAN to WCDMA

0

10

20

30

40

50

60

70

80

90

100

8 8.5 9 9.5 10 10.5 11 11.5 12

Con

ges

tion

Win

dow

s

Time (sec)


Handoff


WCDMA to LAN

0

10

20

30

40

50

60

70

80

90

100

9 9.5 10 10.5 11

Con

ges

tion

Win

dow

s

Time (sec)


Handoff


WCDMA to WLAN

0

10

20

30

40

50

60

70

80

90

100

9 9.5 10 10.5 11

Con

ges

tion

Win

dow

s

Time (sec)


Handoff


WLAN to WCDMA

0

10

20

30

40

50

60

70

80

90

100

9 9.5 10 10.5 11

Con

ges

tion

Win

dow

s

Time (sec)


Handoff

Experiment 2/2


Handoff latency



UDP Handoff Verification 1/3


Switch

AP

InternetInternet

1. WLAN

2. LAN

FH

MH


InternetInternet

WLANFixed Host

Mobile Host

Ethernet

AP

Switch

WLAN

A

B


LAN to WLAN

0

5

10

15

20

25

0 2 4 6 8 10 12 14 16 18 20

Seq

uenc

e N

umbe

r (K

B)

Time (sec)

"LAN""WLAN"

Handoff


WLAN to LAN

0

5

10

15

20

25

0 2 4 6 8 10 12 14 16 18 20

Seq

uenc

e N

umbe

r (K

B)

Time (sec)

"LAN""WLAN"

Handoff

Outline Introduction

Hierarchy Overlay Network Horizontal v.s. Vertical Handoff

Challenge How to achieve seamless vertical handoff ? How to pass NAT gateway ? How to adapt TCP behavior ? How to adapt application behavior ?


Conclusion A Vertical Handoff framework

Support NAT while follows the end-to-end discipline Without an modification to infrastructure

Improve TCP performance CWND Freeze At most 2.3 times the original TCP

Documents

An Agile Vertical Handoff Scheme for Heterogeneous Networks