an agile vertical handoff scheme for heterogeneous networks hsung-pin chang department of computer...
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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
How to pass NAT gateway ? How to adapt TCP behavior ?
Experiments Conclusion
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
How to pass NAT gateway ? How to adapt TCP behavior ?
Experiments Conclusion
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
A Seamless and Proactive End-to-End Solutions for Roaming Across Heterogeneous Wireless Networks (2/4)
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
A Seamless and Proactive End-to-End Solutions for Roaming Across Heterogeneous Wireless Networks (3/4)
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
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
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
Experiments Conclusion
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
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
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
Experiments TCP handoff verification
Handoff latency
TCP handoff performance
UDP handoff verification
TCP Handoff Verification 1/7
InternetInternet
Ethernet
WCDMAFixed Host
Mobile Host
WLAN
NAT
NATBS
B A
C
AP
Switch
Experiment environment
TCP Handoff Verification 2/7
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
TCP Handoff Verification 3/7
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
TCP Handoff Verification 4/7
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
TCP Handoff Verification 5/7
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
TCP Handoff Verification 6/7
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
TCP Handoff Verification 7/7
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
Experiments TCP handoff verification
Handoff latency
TCP handoff performance
UDP handoff verification
Handoff Latency 1/2
WCDMA
InternetInternet
WLAN
Fixed Host
Mobile Host
Ethernet
NAT
AP
Switch
BS
B
A C
Experiment environment
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
Experiments TCP handoff verification
Handoff latency
TCP handoff performance
UDP handoff verification
TCP Handoff Performance 1/8
WCDMA
InternetInternet
WLAN
Fixed Host
Mobile Host
Ethernet
NAT
AP
Switch
BS
B
A C
Experiment environment
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
TCP handoff performance 4/8
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)
"Original""CWND Freeze"
Handoff
TCP handoff performance 5/8
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)
"Original""CWND Freeze"
Handoff
TCP handoff performance 6/8
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)
"Original""CWND Freeze"
Handoff
TCP handoff performance 7/8
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)
"Original""CWND Freeze"
Handoff
TCP handoff performance 8/8
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)
"Original""CWND Freeze"
Handoff
Experiment 2/2
Experiments TCP handoff verification
Handoff latency
TCP handoff performance
UDP handoff verification
UDP Handoff Verification 1/3
Experiment environment
Switch
AP
InternetInternet
1. WLAN
2. LAN
FH
MH
UDP Handoff Verification 1/3
InternetInternet
WLANFixed Host
Mobile Host
Ethernet
AP
Switch
WLAN
A
B
UDP Handoff Verification 2/3
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
UDP Handoff Verification 3/3
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 ?
Experiments Conclusion
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