1. A Comparison of Mechanisms for Improving Mobile IP Handoff Latency for End-to-End TCP
MobiCom 2003
Robert Hsieh and Aruna Seneviratne
School of Electrical Engineering and Telecommunications
The University of New South Wales
26th February, 2004
Presented by Sookhyun, Yang

2. Contents Introduction Related Works Experimental Methodology
Experimental Results
Conclusion

3. Mobility Related Terminology
INTRODUCTION
Mobility Related Terminology
Mobile node (MN)
Handoff (Handover)
Layer 2 handoff
Beacon message
Access router (AR)
Access network (AN)
Mobile IP (MIP)
Handoff latency
Home network (HN)
Foreign (Visited) network
Home Agent (HA)
Foreign agent (FA)
Correspondent node (CN)
Internet draft:

4. Mobile IP (MIP) When a MN moves and attach itself to another network
INTRODUCTION
Mobile IP (MIP)
When a MN moves and attach itself to another network
Need to obtain a new IP address
All existing IP connections to the MN need to be terminated and then reestablished
Solution to this problem at MIP
Indirection provided with a set of network agents
Handoff latency
Address reconfiguration procedure
HA registration process
No modification to existing routers or end correspondent nodes
Foreign network (FN)
reconfiguration
IP’
COS
(Care-of-address) CN FA
tunneling
binding IP
intercept
Binding!!! HA IP IP
Home network (HN)
Mobile node (MN)
Access point (AP)

5. Motivation Effects of Mobile IP (MIP) handoff latency
INTRODUCTION
Motivation
Effects of Mobile IP (MIP) handoff latency
Packet losses
Severe End-to-End TCP performance degradation
Mitigation of these effects with MIPv6 extensions
Hierarchical registration management
Address pre-fetching
Local retransmission mechanism
No comparative studies regarding the relative performance amongst MIPv6 extensions
TCP performance degradation
Perceive these losses as congestion
Cause source throttling or retransmission

6. INTRODUCTION
Overview
Evaluate the impact of layer-3 handoff latency on End-to-End TCP for various MIPv6 extensions
Hierarchical MIPv6
MIPv6 with Fast-handover
Hierarchical MIPv6 with Fast-handover
Simultaneous Bindings
Seamless handoff architecture for MIP (S-MIP)
Propose an evaluation model examining the effect of linear and ping-pong movement on handoff latency and TCP goodput
Optimize S-MIP by further eliminating the possibility of packets out of order

7. Hierarchical Mobile IPv6 (HMIPv6)
RELATED WORKS
Hierarchical Mobile IPv6 (HMIPv6)
Minimize HA registration delay!!
Internet CN HA
RCOA_1
MAP
Mobility Anchor Point (MAP) AR
RCOA_2 AR
binding
binding AR AR AR AR AR AR AR AR AP
MAP act like a local home agent
RCOA_1
LCOA’ AP AP
Macro mobility
Micro mobility
RCOA_2
LCOA’’
Access network
Access network
RCOA_1
LCOA
Internet draft -

8. Local Handoff Latency Reduction
RELATED WORKS
Local Handoff Latency Reduction
Low latency address configuration
Reduce address reconfiguration time
Configure an address for MN in an network likely to move to before it moves
Use L2 trigger
Method
Pre-registration
Perform L3 handoff before completion of L2 handoff
Post-registration
Setup a temporary bi-directional tunnel between oFA and nFA
Allow MN to continue using oFA while registration at the time or later
MIPv6 with Fast-Handover
Combined method of pre-registration and post-registration
Three phases
Handover initiation
Tunnel establishment
Packet forwarding
Pre-registration: perform L3 handoff before it completes the L2 handoff
Beacon signal -> L2 trigger from link-layer ->

9. MIPv6 with Fast-Handover
RELATED WORKS
MIPv6 with Fast-Handover MN
oFA
nFA
Beacon
L2 trigger
RtSolPr(Router solicitation proxy)
Handover
initiation 1
PrRtAdv(Proxy router advertisement)
HI(Handover initiation)
Tunnel
Establishment
btw oFA & nFA 2
F-BU(Fast-binding update)
with COA
Hack(Handover ack)
F-Back(Fast-binding ack)
F-BAck
Disconnect
Forward packets
Packet forwarding
phase 3
Connect
F-NA(Fast neighbor advertisement)
Deliver packets
Internet draft -

10. HMIPv6 with Fast-handover
RELATED WORKS
HMIPv6 with Fast-handover
Combine HMIPv6 with Fast-handover
Reduce latency due to address configuration and HA registration
Relocate the forwarding anchor point from oAR to the MAP
Internet CN HA
MAP
MAP
Forwarding
Forwarding
Low latency handoff == fast handover in Mobile IPv6 AR AR AR AR
nAR AR
nAR
oAR
Access network
Access network

11. Simultaneous Bindings
RELATED WORKS
Simultaneous Bindings
Reduce packet losses
N-casting packets with multiple bindings
Forward packets for a short period to the MN’s current location and to n-other locations where the MN is expected move to
Forwarding carried by oAR, MAP or HA
nAR1
Simultaneous
binding
MAP
oAR
nAR2
AP (Access point)
Internet draft-

12. Seamless Handoff for MIP (S-MIP)
RELATED WORKS
Seamless Handoff for MIP (S-MIP)
Provide a different approach to solve the timing ambiguity problem
Build on HMIPv6 with Fast-Handover
Use MN location and movement pattern to instruct MN when and how handoff is initiated
Decision engine (DE)
Store the history of MN locations
Determine movement pattern
Make “handoff decision” for MN
MAP DE
nAR2
oAR
nAR1 MN

13. Stationary near the center
RELATED WORKS
Decision Engine
MN location
Tracking
<- Signal strength
Handoff
Decision
Linear
Stochastic
Stationary near the center
Handoff mechanism

14. < SPS mechanism >
RELATED WORKS
Handoff Mechanism
Linear movement
Synchronized packet simulcasting (SPS)
Optimized S-MIP
Stochastical manner
oAR and nAR are anticipation-mode
Maintain MN’s binding with oAR, nAR
before F-NA
Reduce unnecessary re-setup
Stationary state near the center
Establish multiple bindings with ARs
MN uses more than one COAs
MAP
optimization DE
S-packet
F-packet
oAR
nAR
S-buffer
F-buffer MN
< SPS mechanism >

15. Optimized S-MIP Elimination of the possibility of packets out of order
RELATED WORKS
Optimized S-MIP
Elimination of the possibility of packets out of order
Upon sending the F-BU to the oAR, MN must immediately switch to the nAR
After receiving F-BU, oAR must immediately forward packets to the nAR
oAR only needs to send the FBAck to the nAR
IP packet filtering mechanism at nAR
oAR incorrectly forwards IP packets with the S-bit set as f-packets
Compare IP packets within the s-buffer and f-buffer at nAR
Discard identical packets in s-buffer
[optimized] Examine 16 bit identification, fragment offset, and flag fields in IP header
Already send..-_- f-packet으로 인식하므로..따라서 s-buffer에서 삭제

16. EXPERIMENTAL METHODOLOGY
Implementation
Simulator
Network Simulator version 2 (ns-allinone2.1b6a)
Patch with the ns wireless extension module allowing basic MIPv4
Extension to the ns-2
Mobile IPv6 protocol
Hierarchical Mobile IPv6 protocol
Fast-handover protocol
Simultaneous bindings protocol
Optimized S-MIP protocol
Modification
Infrastructure mode: WaveLan with connection monitor (CMon)
Additional handoff algorithm: Midway handoff
WaveLan: developed for simulation of wireless ad-hoc networks (broadcast mode)
이 실험에서는 infrastructure mode가 필요하므로 Connection monitor를 추가하여
Cmon이 MN의 packet 수신을 컨트롤한다. 즉, MN이 새로운 access router로 L2-handoff를 시작하면
L2 handoff가 완료될 때까지 모든 패킷을 버린다.
S-MIP의 경우는 MN이 access network의 중간부분에 위치하였을 때 핸드오프를 initiation한다
이와 비슷하게 다른 프로토콜들도 동작하도록 한다

17. Simulation Network Topology
EXPERIMENTAL METHODOLOGY
Simulation Network Topology
Max num of packets received
by the receiver in sequence
Drop policy in router – Drop_tail / RED
< Performance focus >
Handoff delay
TCP goodput
CN’s Congestion window
Overall handoff delay (D) =
time(first-transmitted~retransmitted)
+time(CN->MN)
Micro mobility
Linear / ping-ping

18. EXPERIMENTAL RESULT – Handoff delay
MIPv6 & HMIPv6
Sender (CN)’s view
Time
(seconds)
TCP sequence number
a: MIPv6 (resolution time 100ms)
b~e: HMIPv6 (resolution time 100ms)
f~I: HMIPv6 (resolution time 200ms)
address
resolution L2
handoff BU
at MAP
Out-of-sequence
packet
MIP’s D = 814ms
HMIPv6’s D = 326ms

19. EXPERIMENTAL RESULT – Handoff delay
Fast-Handover
Sender (CN)’s view
Time
(seconds)
TCP sequence number
Proportional to distance (FA~HA)
f ~ i : fast-handover
(resolution time 100ms)
RtSolPr~PrRtAdv BU L2
handoff
D = 358ms
Even though forwarding mechanism,
MN is unable to receive packets until
the binding update is completed

20. HMIPv6 with Fast-Handover
EXPERIMENTAL RESULT – Handoff delay
HMIPv6 with Fast-Handover
< CN’s cwnd >
Receiver (MN)’s view
TCP sequence number
D = 270ms
Packet forwarding
Out-of-sequence packet
Packet loss due to L2 handoff
send (ack)
receive (data)
Time (seconds)

21. EXPERIMENTAL RESULT – Handoff delay
S-MIP
Hand off = 100ms
No packet loss
No out-of-sequence packet
TCP sequence number
Sender (CN)’s view
Time (seconds)
<- Optimized S-MIP
Time (seconds)
TCP sequence number
MAP으로 BU를 보낸 이후에 곧바로 네트웍을 바꾸므로
HMIPv6 with Fast handover == Simultaneous bindings
차이:
No packet loss
Out-of-sequence packet
Non optimized S-MIP ->

22. < Ping-pong case >
EXPERIMENTAL RESULT
Handoff Delay
MIP
HMIPv6
MIPv6 with
Fast-handover
HMIPv6 with
Simultaneous
Bindings
S-MIP (nonop)
S-MIP
814ms
326ms
358ms
270ms
268ms
0ms
< Linear case >
< Ping-pong case >
Completely
break down
Affected
to a lesser extent
Severe throttling
Excellent resilience

23. MN is stationary near the PAR
EXPERIMENTAL RESULT
TCP Goodput
Linear : 1.447s
PP: 14.23s
No handoff: MN is stationary near the PAR
MN is stationary near the PAR

24. Congestion Window EXPERIMENTAL RESULT Linear movement
Ping-ping movement
S-MIP
Simultaneous
Binding

25. Correspondent node (CN)
Conclusion
Analyze various handoff latency reduction framework
Show the possibility of significantly reducing the latency by S-MIP
Optimize the S-MIP scheme
Future works
S-MIP under multiple connection scenarios
Scalability of the Decision Engine (DE)
Design more sophisticated positioning schemes for S-MIP
Correspondent node (CN)