An%20Agile%20Vertical%20Handoff%20Scheme%20for%20Heterogeneous%20Networks

1
An Agile Vertical Handoff Scheme for
Heterogeneous Networks

• Hsung-Pin Chang
• Department of Computer Science
• National Chung Hsing University
• Taichung, Taiwan, R.O.C.

2
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

3
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

4
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

5
Example An Overlay Networks
Campus-wide (3G, GPRS)
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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

lt what we are addressed
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Horizontal Handoff
BSS
BSS
AP
AP
Internet
8
Vertical Handoff
WCDMA
WLAN
AP
BS
Internet
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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

10
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

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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

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A Seamless and Proactive End-to-End Solutions for
Roaming Across Heterogeneous Wireless Networks
(1/4)
Network Applications
User
Kernel
Socket Interface
BSD Sockets
TCP
UDP
Transport Layer
LCT Table Translation
IP
Network Layer
PPP
SLIP
Ethernet
Network Devices
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A Seamless and Proactive End-to-End Solutions for
Roaming Across Heterogeneous Wireless Networks
(2/4)
L A N
L A N
Original address Original port Mapped address Mapped port
A p1 C p2
Original address Original port Mapped address Mapped port
A p1 A p1
Original address Original port Mapped address Mapped port
A p1 C p2
Original address Original port Mapped address Mapped port
A p1 A p1

W L A N
Mobile Client
Fixed Host
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A Seamless and Proactive End-to-End Solutions for
Roaming Across Heterogeneous Wireless Networks
(3/4)
Application
Application
A B
A B
Kernel
Kernel
Handoff Layer
Handoff Layer
Table Lookup
Table Lookup
C B
?3 ????????
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A Seamless and Proactive End-to-End Solutions for
Roaming Across Heterogeneous Wireless Networks
(4/4)

• Problems
• NAT issue
• Require an S/N (Subscription/Notification) Server
• Modify the infrastructure
• TCP performance
• Do not consider

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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

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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

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Problem
Fixed Host
New IP address
NAT
Switch
Ethernet
Update
WLAN
AP
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Solution
Fixed Host
Old IP address
NAT
Switch
Ethernet
Update
WLAN
AP
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Outline

• Motivation
• Related work how to achieve seamless vertical
  handoff ?
• Challenge and Contribution
• How to pass NAT gateway ?
• How to adapt TCP behavior ? gt CWND-Restore
• Experiments
• Conclusion

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How to adapt TCP behavior ?

• Problem
• TCP consider packet loss as network congestion
• Slow down
• Butnow packet lose is because handoff
• Solution
• CWND-Restore

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CWND-Restore
Fixed Host
CWND 20
CWND 2
CWND 50
NAT
Switch
Ethernet
WLAN
AP
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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

24
System Implementation- Linux Kernel 2.6.11
Applications
User Mode
Kernel Mode
TCP
UDP
CWND-restore
Connection Manager
Handoff Detection
IP
Ethernet Driver
WLAN Driver
3G
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Experimental Platform
Fixed Host Mobile Host
CPU AMD XP 2600 Intel Pentium M 1.4GHz
RAM 512 MB 256 MB
NIC 1 100Mbps Ethernet 100Mbps Fast Ethernet Ethernet
NIC 2 Philips 802.11g WLAN miniPCI Adapter
NIC 3 Novatel UMTS/WCDMA USB Adapter
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Experiment 2/2

• Experiments
• TCP handoff verification
• Handoff latency
• TCP handoff performance
• UDP handoff verification

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Experiment 2/2

• Experiments
• TCP handoff verification
• Handoff latency
• TCP handoff performance
• UDP handoff verification

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TCP Handoff Verification 1/7
Experiment environment
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TCP Handoff Verification 2/7

• LAN to WLAN

Handoff
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TCP Handoff Verification 3/7

• WLAN to LAN

Handoff
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TCP Handoff Verification 4/7

• LAN to WCDMA

Handoff
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TCP Handoff Verification 5/7

• WCDMA to LAN

Handoff
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TCP Handoff Verification 6/7

• WLAN to WCDMA

Handoff
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TCP Handoff Verification 7/7

• WCDMA to WLAN

Handoff
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Experiment 2/2

• Experiments
• TCP handoff verification
• Handoff latency
• TCP handoff performance
• UDP handoff verification

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Handoff Latency 1/2
Experiment environment
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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
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Experiment 2/2

• Experiments
• TCP handoff verification
• Handoff latency
• TCP handoff performance
• UDP handoff verification

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TCP Handoff Performance 1/8
Experiment environment
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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
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TCP handoff performance 3/8

• LAN to WLAN

Handoff
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TCP handoff performance 4/8

• WLAN to LAN

Handoff
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TCP handoff performance 5/8

• LAN to WCDMA

Handoff
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TCP handoff performance 6/8

• WCDMA to LAN

Handoff
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TCP handoff performance 7/8

• WCDMA to WLAN

Handoff
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TCP handoff performance 8/8

• WLAN to WCDMA

Handoff
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Experiment 2/2

• Experiments
• TCP handoff verification
• Handoff latency
• TCP handoff performance
• UDP handoff verification

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UDP Handoff Verification 1/3

• Experiment environment

Internet
Switch
2. LAN
AP
FH
1. WLAN
MH
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UDP Handoff Verification 1/3
Internet
Switch
AP
B
Mobile Host
A
WLAN
Fixed Host
Ethernet
WLAN
50
UDP Handoff Verification 2/3

• LAN to WLAN

Handoff
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UDP Handoff Verification 3/3

• WLAN to LAN

Handoff
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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 ?
• Experiments
• Conclusion

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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