Transcript Inter-Subnet Mobile IP Handoff in 802.11b Wireless LANs

Modularized Two-Stages
Vertical Handoff Scheme
in Integration of WWAN and WLAN
Shimin Li
Ying Wang
Presented by
Shimin Li
E&CE750
Second part of presentation of our report

Recall the first part of presentation

Motivation and Objective

Overview of WWAN and WLAN
Integration of WWAN and WLAN
Modularized Vertical Handoff Scheme



Decision module
Presentation Overview


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

Mobile IP
Vertical Handoff Delay
Related works
Solutions
Modularized Vertical Handoff Scheme
 Action



Module
Performance Analysis
Discuss
Conclusion
Mobile IP
This diagram comes from ECE750 lecture slides
Mobile IP

cont’d
Basic Mobile IP
 MN
has a permanent IP address
 When moving to foreign network, MN detects a FA
and obtains a CoA, and registers the CoA with HA
 HA tunnels all packets of MN to FA or MN itself
using the CoA
 CoA can be Foreign Agent CoA or Co-located CoA
Mobile IP
cont’d
This diagram comes from ECE750 lecture slides
Mobile IP
 Optimized
 CN
cont’d
Mobile IP
requests the current location of MN from HA. HA
returns the CoA of MN via an update message. Then
CN caches the CoA and send packets directly to the
current foreign agent FA or MN itself. Encapsulation
of data for tunneling to the CoA is now done by CN,
not HA
 Solve triangular routing problem
Mobile IP

cont’d
Assumption about MIP
 Vertical
handoff scheme is based on MIPv4
 CoA is a Foreign Agent CoA, not Co-located CoA
Vertical Handoff Delay
Vertical Handoff Delay cont’d

Definition
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Vertical handoff delay = D1 + D2 + D3
Analysis
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D1 depends on movement and is out of control, we assume
that D1 is relatively small
D2 and D3 can be minimized using intelligent handoff scheme
Related work

Proposed mechanisms addressing reducing delay



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H. Park et al. reduced delay by adding two structures to the
integration: Mobile Agent and Subnet Agent
S. Sharma et al. introduced OmniCon: a MIP-based vertical
handoff system for integration of WLAN and GPRS[2]
Ye Min-hua et al. used RSS triggering and multi-tunneling to
address WLAN/GPRS integration based on Basic MIPv4[3]
Q. Zhang et al. proposed a subscription/notification service in
vertical handoff system based on MIPv4 to handle simultaneous
movements and provide transparency to NAT[4]
Solutions

For minimizing D2
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For minimizing D3
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

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Divide handoff procedure into two steps
Perform advance registration
Allow MN to communicate with FAnew while still connected to FAold
For reducing packet loss


Sense physical and MAC layer
Copy and tunnel packets for MN to FAnew even before handoff has
been finished
For easy implementation and application transparency



Vertical handoff is based on MIP
Only modify the entities of MIP such as MN, HA, and FA
Modularize the handoff system
Modularized Vertical Handoff Scheme

Modularization
 Decision
Module
 Action Module
Recall the Decision Module


Trigger handoff actions
How?
 By


sending messages to Action Module:
Per-handoff message
Handoff message
Action Module

Perform vertical handoff actions
 Per-handoff
actions
 Handoff actions
 Undo actions

Triggered by messages from Decision Module
Action Module

cont’d
Per-handoff actions
 Triggered
by Per-handoff messages
 Four scenarios:
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


From WWAN to WLAN based on Basic Mobile IP
From WWAN to WLAN based on Optimized Mobile IP
From WLAN to WWAN based on Basic Mobile IP
From WLAN to WWAN based on Optimized Mobile IP
Action Module
cont’d
Action Module
cont’d
Action Module
cont’d
Action Module
cont’d
Action Module

cont’d
Handoff actions
 Triggered
by Handoff messages
 Four scenarios:



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From WWAN to WLAN based on Basic Mobile IP
From WWAN to WLAN based on Optimized Mobile IP
From WLAN to WWAN based on Basic Mobile IP
From WLAN to WWAN based on Optimized Mobile IP
Action Module
cont’d
Action Module
cont’d
Action Module
cont’d
Action Module
cont’d
Action Module

cont’d
Undo action


Undo per-handoff action
How?

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
MN sends undo message to HA via FAnew. After receiving the message,
FA or CN stops copying packets and tunneling them to FAnew, and
FAnew cleans its buffer
After that MN communicates with it original network normally
When?
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
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The timer in Action Module reaches T0, a constant
Whenever starting per-handoff action, the timer starts
After handoff action or undo action, the timer stops and is reset to zero
Performance Analysis
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Purpose
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Approaches
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Verify contribution of two-stage scheme
Verify contribution of physical layer and MAC layer sensing
Compare with other mechanisms
Tools


The network simulator: NS-2, or
Writing a specific simulator using Java or Matlab
Discuss

Limitations

Not compatible with Network Address Translation (NAT)



Not support simultaneous movement


MN behind NAT Gateway allocates a private IP address
MN has no routable IP address so it is impossible to establish
a link to HA
Possibility is very low
Extension to Mobile IPv6


CoAs are co-located, no FA needed
Adding an additional server at router to provide data buffer and
forward the buffered packets to MN as the FA in MIPv4
Conclusion
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Physical layer and MAC layer sensing decrease latency contributed
by detecting new FA and obtaining new CoA
Two-stage mechanism significantly reduces latency by doing some
registration work in advance
Multi-tunneling decreases packet loss, and cost due to multitunneling can be very low since multi-tunneling lasts very short
Modularization provides a easy implementation
Only modification of Mobile IP entities provides high compatibility
and transparency to application
The vertical handoff scheme can be applied to real-time application
Selected references
1. Hyosoon Park, Sunghoon Yoon, Taehyoun Kim , Jungshin Park, Misun Do,
and
Jaiyong Lee; “Vertical Handoff Procedure and Algorithm between
IEEE802.11 WLAN and CDMA Cellular Network”
2. Srikant Sharma Inho Baek Yuvrajsinh Dodia Tzi-cker Chiueh; “OmniCon: A
Mobile IP-based Vertical Handoff System for Wireless LAN and GPRS Links”
3. M.Ye, “The mobile IP handoff between hybrid networks”, IEEE, 2002
4. Q. Zhang, C. Guo, Z. Guo, and W. Zhu, “Efficient mobility management for
vertical handoff between WWAN and WLAN” IEEE Commun. Mag., vol. 41,
pp. 102–108, Nov. 2003
Thanks