Download Friends Troubleshooting Network J. Wang*, Y. Hu§, C. Yuan*, Z

Friends Troubleshooting Network
J. Wang*, Y. Hu§, C. Yuan*, Z. Zhang*, Y. Wang*.
* Microsoft Research
§U.C.
Berkeley
Presentation for course 20 ECES 728
by Kaushik Chowdhury
OUTLINE
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Problem Definition
Motivation
PeerPressure – A Solution!
Assumption & Design Considerations
Protocol Details
Attacks and Defences
Experimental Results
Motivation
17% of total cost of ownership
= Configuration costs
Windows registry/UNIX resource files
Third party software
Define “perfect” configuration
Human time and effort
Ownership
Cost
Peer-Pressure – A Solution!
P( S ) 
1
t
P (V / S ) 
P( S / V ) 
P( H )  1 
1
t
1
m
P (V / H ) 
c
N
P(V / S ) P( S )
P(V / S ) P( S )  P(V / H ) P( H )
FTN - Assumptions
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Friends contribute authentic/relevant/ non-privacy
compromising information
Recursive trust, not transitive trust
Privacy through history less /futureless Random Walk
Destination free searching/Routing
FTN-Approaches
Integration of Search & Aggregation
● Separate search step may return IP address of helpers
● Helps determine the applications running on Helper’s m/c
● Parameter value represents collective state
History less & futureless Random-Walk
● No information is present on nodes covered or to-be
covered
● The reply follows the same path back
FTN-Protocol Design
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Step #1 Creating a request
Remove all entries that contain usernames
Form the “FTN REQUEST”
Each request is identified with
H(n,All Entry Names)
FTN-Protocol Design…contd
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Step #2 Forward
Path Aggregation
Sick m/c establishes
secured channel.
Request is sent
Friend replies with
ACK/NACK
 Node becomes helper
with probability Ph
Friend
Sick 4
REQ:
Secured channel
ACK:
NACK:
5
FTN-Protocol Design…contd
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Use of Ph
Second-last hop can infer last hop’s information
Counter! Poll last hop with fake requests and then
analyze statistically
Solution: Bimodal Ph – Ph takes smaller value with
small R
R=1, e=0
R=0, e=1
FTN-Protocol Design…contd
Last hop and Return Path
If R=0, node waits for random amount
of time, and then sends reply back
Without random wait, previous node
can launch polling attack
Sick node subtracts random value
initialization and performs Peer-Pressure
diagnosis
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FTN - Challenges
Compromised friends!
Node remembers the value of R when the
request message passed by
Node forwards reply if:
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(a)
(b)
(c)
Number of additional matches does not exceed R
Count in value distributions does not decrease
Sum of all counts in Reply – Sum of all counts in
Request = R
An Example
FTN - Challenges
Sybil Attack
Malicious nodes collude in the attack
Counter: Send multiple troubleshooting
requests hoping that majority will return
correct results
The earlier a compromised node appears in
the path, more is the damage
High fan out thus reducing R
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Example of Sybil Attack
R is large:
One compromised
node can bring in
a host of others
Countering Sybil Attack
R is small:
Need a larger fanout. Hence effect of
compromised path
can be avoided!
Gossip Attack
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Ph + history less +futureless strategy
can mitigate most attacks except one:
Victim is between two gossipping friends, including
sick friend
Whenever victim ‘helps’ information can be inferred
by the two gossipers
Solution: Random Perturbation: Adding of a random
noise than incrementing
Results & Experimentation
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Peer Pressure could pin-point the root-cause
misconfiguration in 12 out of 20 real-world
troubleshooting examples
Types of Suspects
Related Work
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FreeNet : Distributed Anonymous
Information Storage/Retrieval
Crowds : Anonymous Web Transactions
These require point to point communications & FTN
is destination free
Problem of privacy-preserving similar to
secure/private voting
Differences between voting
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Voters need to be authenticated by a
centralized authority
Participation privacy
Voting requires precise vote tallies
Other work like that in sensor networks
involve identity revealing authentication if
integrity of data is to be ensured.