virtual router kien a. hua data systems lab school of eecs university of central florida
TRANSCRIPT
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VIRTUAL ROUTER
Kien A. Hua
Data Systems LabSchool of EECS
University of Central Florida
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Outline
• Mobile Ad Hoc Networks
• Virtual Router Approach
– Routing
– Data Forwarding
• Cooperation Enforcement in Virtual Router Approach
• Simulation Results
• Conclusions
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Wireline Communications
Router
Router
Router
Router
S
D
Router
Infrastructure
Routers help forward data
packets
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What is Mobile Ad Hoc Network?
→ All nodes participate in the routing and data forwarding process.
Source Node
Destination Node
Infrastructureless
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Route Request
Source Node
Destination Node
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Route Reply
Source Node
Destination Node
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Data Transmission
Source Node
Destination Node
The selected nodes participate in the data forwarding process
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Link Break
Source Node
Destination Node
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Issue Route Request
Source Node
Destination Node
Selected New Route
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Handling High Mobility
• Using Physical Nodes as Routers:
Mobility → link breaks → reroute → overhead !
• Using Virtual Routers:
Virtual routers are stationary → links are robust → fewer reroute → less overhead !
Virtual Router
SD
SD
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What is a Virtual Router ?
• A virtual router is a spatial area
• Physical nodes within this area alternate in forwarding data
• When a node leaves the area, it is no longer obliged to forward the data
→Virtual router is stationary
→More suitable for high mobility applications such as vehicular networks
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Virtual Router
SD
X
Y
Z
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Virtual Router – Example
How to apply this concept to vehicular network ?
Each cell is a virtual router
Source Node
Destination Node
Each node has GPS & grid map
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Street Environment: Mobility Model
• Streets constrain node mobility
• Nodes can pause and change direction at intersections.
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Street Environment: Radio Range
Buildings block radio signal → Often no link between nodes on different streets→ Broadcast range is not a circle
14
Mobile Node m
Str
eet
Street
Mobile Node m
Street
Mobile Node m
Str
eet
Street
Cannot establish direct communication
due to the building
Mobile Node m
Str
eet
Street
Cannot establish direct communication
due to buildings
Radio Range of
m
Effective Radio
Range of m
Mobile Node m
Street
Cannot establish direct communication
due to the building
Mobile Node m
Street
Cannot establish direct communication due to buildings
Radio Range of
m
Effective Radio
Range of m
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Virtual Routers in Street Environment
• Streets are divided into small cells:
– Each intersection is an intersection cell
– A long road block can be divided into multiple block cells
• Radio range must cover any 2 consecutive cells
• Each cell is a virtual router
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Buildings
Buildings
Cell A Cell B Cell C
Cell A Cell B
Buildings
Buildings
Cell A Cell DCell B Cell C
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Vehicular Network UsingVirtual Routers
• “Green” virtual routers form a connecting path between source and destination
• Data are transmitted from source to destination over these virtual routers
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Source
Destination
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Location Discovery
• A source node broadcasts a Location Discovery (LD) packet
• This LD packet propagates until it reaches the destination node
• When the LD packet arrives at the destination, it replies with a Location Reply (LR) packet that includes the location of the destination router (i.e., destination cell).
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Similar tostandard
route request
Subsequently, every data packet carries the ID’s of the source and destination routers
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Data Forwarding: Reference Line
Every data packet carries the locations of Source and Destination
Reference line (RL) is the straight line connecting the center of the source router and the center of the destination router
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Source node
Source Cell
Destination Cell
DestinationNode
Source node
),( DD YX
),( SS YX
Mid-Point ofSource Cell
Source Cell
Reference Line
Destination Cell
DestinationNode
Mid-Point of aDestination Cell
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Data Forwarding: Reference Points
Reference points (RP’s) are the intersections of the reference line and the streets
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Source node
),( DD YX
),( SS YX
Mid-Point ofSource Cell
Source Cell
Reference Line
Destination Cell
DestinationNode
Mid-Point of aDestination Cell
Center of Streets
Reference Point
Reference Line
Center of Streets
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Data Forwarding: Forwarding Zones
• There is one forwarding zone for each reference point
• Three horizontal and two vertical forwarding zones in this example
• Some forwarding zones overlap
• The forwarding zones make up the grid path for data forwarding
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Source node
Reference Point
DestinationNode
Source node
Reference Point
DestinationNode
Forwarding Zone
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Data Forwarding
• Virtual routers within the forwarding zones are selected for data forwarding
• When a node leaves the forwarding area, it is no longer obliged to forward data.
• If a node enters the forwarding area, this node must participate in the data forwarding.
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Source node
Reference Point
DestinationNode
Forwarding Zone
Source node
DestinationNode
Selected Grid Path
How to do route maintenance
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Connection Maintenance
Destination node moves away from current router
→ Reference line changes
→ Reference points changes
→ Forwarding zones changes
→ Need a new connection path
Route Maintenance:
–The destination node periodically updates its location with the source node.
– If this fails, source issues a location discovery packet
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Essentially no
overhead
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Selfish and Malicious Behavior
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Source node
DestinationNode
Selected Grid Path
Malicious Node
It works as long as nodes cooperate
Need cooperation
enforcement !!
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Cooperation EnforcementStep 1: Detect Malicious Node
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Malicious node
Malicious behavior detected
Malicious behavior detected
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Cooperation EnforcementStep 2: Penalize Malicious Nodes
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Malicious Node tries to establish
connection by broadcasting
Location Discovery packet
radio range of malicious node
Location Discovery packet is
blocked by the building
Location Discovery packet is
blocked by the building
I know about the
misbehavior
I know about the
misbehavior I know about the
misbehavior
No one will forward the Location
Discovery packet for the malicious
node.
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Network Layer Structure
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Routing Layer (Network) Routing Layer (Network)
MAC Layer (Data Link) MAC Layer (Data Link)
Radio Layer (Physical) Radio Layer (Physical)
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3C Module
27
Routing Layer (Network) Routing Layer (Network)
3C MODULE(Temper Resistant)
3C MODULE(Temper Resistant)
MAC Layer (Data Link) MAC Layer (Data Link)
Radio Layer (Physical) Radio Layer (Physical)
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3C Module - Overview
• It maintains three Counters:
– Forward Request Counter: Number of forward requests (both discovery and data packets) received by a node.
– Forward Counter: Number of packets forwarded by a node.
– Location Discovery Counter: Number of Location Discovery packets initiated by a node (i.e., number of connections requested)
• It adds a 3C header which contains the values of these three counters to every Location Discovery packet.
• Based on this header, neighboring nodes analyze the behavior of the source node, and decide to forward or discard the packet (i.e., penalize the source node)
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Misbehavior Detection: Overview
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Routing Layer (Network) Routing Layer (Network)
3C MODULE(Temper Resistant)
3C MODULE(Temper Resistant)
MAC Layer (Data Link) MAC Layer (Data Link)
Radio Layer (Physical) Radio Layer (Physical)
Add 3C header
Examine 3C header for
misbehavior
Examine 3C header again
before forwarding
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Route Discovery
• Source node initiates Route Request packet
• Intermediate nodes forward the packet until it reaches the Destination node
• The Destination node receives the Route Request packet and sends back a Route Reply packet
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S D
Request
Request
Request
Request
Let’s look at the operation at these nodes
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Initiate Location Discovery
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Establish a connection
Routing Layer (Network)
3C MODULE
(Temper Resistant)
No
Upper Layer
Yes
MAC Layer(Data Link)
Perform Location Discovery
procedure
Add 3C header to the packet This is a new
communication request
This is a reroute request
An ongoing communication
session?
Increment Location Discovery Counter
Broadcast location discovery packet
Add to Session Table
Submit a route request
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Routing Layer (Network)
Receive Location Discovery
32
MAC Layer(Data Link)
3C MODULE
(Temper Resistant)
Yes
No
Yes Misbehavior Detection
No
Yes
Is from misbehavior
node?
No
No
Yes
Discard Packet
VRA Protocol
Need to detect
misbehavior?
MISBEHAVIOR DETECTION MODULE
Is the packet in Session Table?
More on this module later…
Insert new request into
Session Table
The forwarding node initiates
this route request
Increment Forward Request
Counter
Reset TTL for this entry
Penalize the requester
Location discovery packet arrives
Initiated by
sender?
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VRA ProtocolRouting Layer (Network)
Forward Location Discovery (1)
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3C MODULE
(Temper Resistant)
Yes(Reply)
No Is destination node?
Start delay period Discard Packet
YesNo
Have seen the packet before?
YesHear same
packet from a neighbor node?
No No
End of Delay?
Yes(Forward)
The Virtual Router has already
forwarded the packet
The route has been found
Increment Forward Request
Counter
Reset TTL for this entry
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3C MODULE
(Temper Resistant)
Forward Location Discovery (2)
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Routing Layer (Network)
Yes(Reply)
Is destination node?
Yes(Forward)
End of Delay?
MAC Layer(Data Link)
Increment Forward Counter
Broadcast location discover/reply packet
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3C MODULE
(Temper Resistant)
Network Attack:Sending Dummy Packets
35
Routing Layer (Network)
Discard PacketNo
MAC Layer(Data Link)
Ispacket in SessionTable?
Increment Forward Counter
Broadcast location discover/reply packet
Generate & “forward” a dummy route request packet
Flood the network with a dummy record
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Data Transmission
• Source node transmits a data packet
• Intermediate nodes forward the packet until it reaches the Destination node
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S D
Data Data Data Data
Let’s look at the data forwarding operation at a node
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Receive Data Packet
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MAC Layer(Data Link)
3C MODULE
(Temper Resistant)
Data packet arrives
Yes
No
Routing Layer (Network)
Ispacket in SessionTable?
Insert new request into
Session Table
Reset TTL for this entry Increment
Forward Request Counter
VRA Protocol
Forwarding Procedure in
VRA
A node new to the virtual router might not know about this on-going session
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VRA ProtocolRouting Layer (Network)
VRA Protocol Forwarding Procedure (Data Packet)
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3C MODULE
(Temper Resistant)
No Is destination node?
Start delay period Discard Packet
YesNo
Have seen the packet before?
YesHear same
packet from a neighbor node?
No No
End of Delay?
Increment Forward Request
Counter
Reset TTL for this entry
These steps are the same as in Location
Discovery packet
Yes
The packet has reached its destination
Yes
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3C MODULE
(Temper Resistant)
Forward Data Packet
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Routing Layer (Network) Is destination
node? End of Delay?
MAC Layer(Data Link)
Increment Forward Counter
Broadcast Data Packet
Yes
Yes
Receive Data Packet
Packet arrives at destination
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3C MODULE
(Temper Resistant)
Network Attack: Dummy Packets
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Routing Layer (Network)
Discard PacketNo
MAC Layer(Data Link)
Ispacket in SessionTable?
Increment Forward Counter
Broadcast Data Packet
Generate & “forward” a dummy data packet
Flood the network with a dummy record
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Routing Layer (Network)
Receive Location Discovery
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MAC Layer(Data Link)
3C MODULE
(Temper Resistant)
Is initiated by last hop?
Yes
No
Yes Misbehavior Detection
No
Yes
Is from misbehavior
node?
No
No
YesDiscard Packet
VRA Protocol
Need to detect
misbehavior?
MISBEHAVIOR DETECTION MODULE
Is the packet in Session Table?We now discuss this module
Insert new request into
Session Table
Increment Forward Request
Counter
Reset TTL for this entry
Location discover packet arrives
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Misbehavior Detection Metrics
3C Module at each node i maintains the following information:
– Forward Ratio (FR): Percentage of arriving packets forwarded
• FRi =
– Local Average Forward Ratio (LAFR)
• LAFRi = ,
where, n is the number neighbor nodes of i
– Request Ratio (RR): Offer enough service to use the network ?
• RRi =
42
i
i
unterForward Co
CounterDiscovery Location
i
i
Counter questForward Re
unterForward Co
1
)(1
n
FRFR i
n
jj
Forward Request Counter Number of forward requests (both discovery and data packets) received by a node.
Forward Counter Number of packets forwarded by a node.
Location Discovery CounterNumber of Location Discovery packets initiated by a node (i.e., number of connections requested)
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Initiate Misbehavior Detection
43
m n
Location Discovery packet
Is the forwarder the initiator of this
packet ?
If m is not the source node, n
proceeds to forward the
packet
else, n checks 3C header of this packet.
Need to establish a
communication connection with
someone
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m is a suspect
Misbehavior Detection: Check Forward Ratio
44
m n
Location Discovery packet
FRm < FRn → n suspects m
has been dropping packets
FRn = n
n
Counter questForward Re
unterForward CoFRm =
m
m
Counter questForward Re
unterForward Co
FRm < FRn means that n is not forwarding enough
packets
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m is a suspect
Misbehavior Detection:Check Request Ratio
45
m n
Location Discovery packet
RRm > 1.2*RRn → n suspects m
has been dropping packets
RRm > 1.2 ∙ RRn means that m made many connection
requests; but it has not provided enough service to
other nodes.
RRm = i
i
unterForward Co
CounterDiscovery Location RRn =
i
i
unterForward Co
CounterDiscovery Location
n needs to exchange counter information with
neighboring nodes
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Initiate Misbehavior Detection:Compare to Local Average
46
m n
x
y
n exchanges counters
information with neighboring
nodes
FRm < LAFRn → m is a suspect
according to local average
LAFRn =
1
)(1
k
FRFRk
ini
k is the number of neighbor nodes of n
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Enter Detection Mode: Listening State
47
m n
x
y
m is a suspect. Enter Detection
mode – Listening State
m is a suspect. Enter Detection
model – Listening State
m is a suspect. Enter
Detection mode –
Listening State
n enters Detecting state
by invoking Misbehavior
Detection procedure.
Radio range of m
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Detection Mode: Detecting State (1)
48
m n
x
y
x resets the delay timer and
stays in Listening State
y resets the delay timer and
stays in Listening State
n generates and
broadcasts a Detection
packet
n broadcasts a Detection packet two more times
Detection packet is just a dummy data packet
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Detection Mode: Detecting State (2)
49
m n
x
y
x exits Listening
State
y exits Listening
State
n exits Listening
State
If m forwards the Detection packet
n forwards m’s Location Discovery
packet
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Detection Mode: Detecting State (3)
50
m n
x
y
x marks m as misbehavior
y marks m as misbehavior
n marks m as misbehavior
If m drops all three Detection packets
x drops m’s LocationDiscovery pakcet
n drops m’s Location
Discovery packet
y drops m’s Location
Discovery packet
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Simulation Setting
• Simulator: GloMoSim.
• Constant-bit-rate sessions of 512-byte packets.
• Radio propagation range is 375 meters, and channel capacity is 2 Mbits/sec.
• Street width is 10 meters, and building block size is 100m by 100m.
• Initial nodes placement: 2 nodes per intersection, and 8 nodes per block.
• Mobility model: At intersections, a node pauses for a period of time, and then probabilistically changes its direction of movement.
• Speed: random between 0 m/s and 25 m/s (or 56 miles/hr).
• Pause time: random between 0 and 20 seconds.
• 100 simulation runs with different seed numbers for each scenario.
• Number of misbehaving nodes: 5%, 10%, 20%, and 30% of total number of nodes.
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Schemes and Malicious Behavior
• Schemes compared:
Reference scheme: All nodes act collaboratively and relay data for each other.
Defenseless scheme: No detection mechanism is implemented. The network is totally “defenseless”.
3CE (3-Counter Enforcement) scheme: misbehaving nodes are detected and punished.
• Malicious Behavior:
A malicious node recognizes that it is being punished when its Location Discovery packet has been dropped four consecutively times.
Once malicious nodes recognize the punishment, they participate in data forwarding to rejoin the network.
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Performance Metrics
• Packet Delivered Ratio (P)– Percentage of data packets successfully delivered
to their destination.
• Misbehaving Node Detection Ratio (D)– Percentage of misbehaving nodes detected
• False Accusation Rate (F)– Percentage of detected nodes incorrectly accused
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Packet Delivered Ratio (P)
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• 3CE is significantly better than the defenseless system
• 3CE incurs little overhead. Its performance does not decrease significantly compared to the Reference scheme.
Reference
VRA
Defenseless
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Misbehaving Node Detection Ratio (D)
Detection Ratio
Speed (m/s) 10 15 20 25
5% misbehaving nodes 89% 88% 83% 81%
10% misbehaving nodes 93% 91% 86% 88%
20% misbehaving nodes 91% 85% 89% 87%
30% misbehaving nodes 91% 87% 84% 85%
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Average about 87%
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False Accusation Rate (F)
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False Accusation Ratio
Speed (m/s) 10 15 20 25
5% misbehaving nodes 0% 2% 3% 2%
10% misbehaving nodes 1% 2% 2% 3%
20% misbehaving nodes 1% 1% 2% 2%
30% misbehaving nodes 2% 2% 4% 5%
• Overall, false accusation is very low.
• False accusation is higher when nodes move faster.Suspect node forwards the detection packet after moving out of the
radio range of the detecting nodes causing false accusation (i.e., not forwarding the detection packet)
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Forward detection packet
Send detection packet
False Accusation
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m n
m is badFalse accusation
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Conclusions
• The Virtual Router approach has been shown to provide better performance than standard routing based on physical nodes
• 3CE (3 Counters Enforcement) cooperation enforcement technique further improves the Virtual Router approach
• Our simulation results indicate:
– improved network throughput (better data delivery rate)– effective detection of most (87%) misbehaving nodes – almost no false accusation