Post on 27-Dec-2015
Exploiting super peers for large-scale peer-to-peer Wi-Fi roaming
Exploiting super peers for large-scale peer-to-peer Wi-Fi roamingEfstratios G. Dimopoulos, Pantelis A. Frangoudis and George.C.PolyzosEfstratios G. Dimopoulos, Pantelis A. Frangoudis and George.C.Polyzos
MotivationMotivation
Very high Wi-Fi density in cities The case for Skyhook Residential Wi-Fi hotspots with excess
capacity How to exploit this user-provided
infrastructure? We need a Wi-Fi sharing scheme! Can community based Wi-Fi access
complement cellular?
Very high Wi-Fi density in cities The case for Skyhook Residential Wi-Fi hotspots with excess
capacity How to exploit this user-provided
infrastructure? We need a Wi-Fi sharing scheme! Can community based Wi-Fi access
complement cellular?2
Design optionsDesign options
Centralized Permanent IDs Full view of
transactions Easy to detect
misuse
FON
Centralized Permanent IDs Full view of
transactions Easy to detect
misuse
FON
3
Decentralized Free/disposable IDs Enhances privacy Should discourage
misuse
Our approach
Decentralized Free/disposable IDs Enhances privacy Should discourage
misuse
Our approach
4
Our approachOur approach
Design principle Users form a club that relies on indirect
service reciprocity
Distinct characteristics Fully decentralized No user registration Designed with off-the-shelf equipment in
mind Does not assume altruists
Design principle Users form a club that relies on indirect
service reciprocity
Distinct characteristics Fully decentralized No user registration Designed with off-the-shelf equipment in
mind Does not assume altruists
5
EntitiesEntities
Peer: provides service via home AP, consumes when mobile
Peer ID: uncertified public/private key pair
Accounting unit: digital receiptSigned by roaming userProof of transaction
Receipt repositories
Peer: provides service via home AP, consumes when mobile
Peer ID: uncertified public/private key pair
Accounting unit: digital receiptSigned by roaming userProof of transaction
Receipt repositories
6
Receipts and the reciprocity algorithm
Receipts and the reciprocity algorithm
Consuming member CertificateConsuming member Certificate
TimestampTimestamp
Member SignatureMember Signature(Signed with member private key)(Signed with member private key)
Weight (amount of bytes relayed)Weight (amount of bytes relayed)
Contributor Public KeyContributor Public Key Receipt generation
AP periodically requests fresh receipt
Roamer sends signed receipt
Storage Receipt repositories Input to the reciprocity
algorithm
Algorithm output Indirect Normalized Debt
(IND) Translated to QoS
Receipt generation AP periodically requests
fresh receipt Roamer sends signed
receipt
Storage Receipt repositories Input to the reciprocity
algorithm
Algorithm output Indirect Normalized Debt
(IND) Translated to QoS
8
The locality of visitsThe locality of visits
Visits to foreign areas are rare
IND ≈0Receipts are
unvalued in foreign areas
Visits to foreign areas are rare
IND ≈0Receipts are
unvalued in foreign areas
9
A Super-Peer-assisted architecture
A Super-Peer-assisted architecture
At least one Super Peer per Area
Super Peers:• Globally known
• Trusted
• Without extra computational capabilities
10
An algorithm for large-scale roaming - Specification
An algorithm for large-scale roaming - Specification
The algorithm should run for all transactions (not only for roaming ones) Low Complexity As few Super Peers as possible Super peers should be used only when
necessary
Incentive based Normal users
To contribute service to Super Peers To contribute service to roamers
Super Peers To mediate other transactions
The algorithm should run for all transactions (not only for roaming ones) Low Complexity As few Super Peers as possible Super peers should be used only when
necessary
Incentive based Normal users
To contribute service to Super Peers To contribute service to roamers
Super Peers To mediate other transactions
11
P2PWNC AREA
ExampleExample
Green Team
HOME P2PWNC AREA
Team Server
Home Super Peer
Team Server
A user visits a foreign areaHe asks service from an AP and informs the AP about the SP of his home area
Visited Super Peer
Team Server
Team Server
The team server runs the reciprocity
algorithm
According to the result he should not contribute service. So, he asks the SP of his home location
to find a guarantor, in order to provide service to the user
Simultaneously asks from the user’s home location SP to calculate the same quantity and
the waits for the answer.
The VSP runs the reciprocity algorithm for
the prospective consumer, in order to calculate the quantity (IND) that he is able to
guarantee.
The HSP runs the reciprocity algorithm in order to calculate
the IND for the prospective consumer
Informs the VSP for the calculated IND
VSP calculates:1. The final IND for the
prospective consumer. 0,2xIND (VSP) + 0,8xIND(HSP)
2. The guarantor SP for this transaction.
Informs the HSP (guarantor) and the Team Server of the provider about the IND calculated
AP asks receipts from the SP for his own use and also from the consumer on behalf of the SP
The consumer signs receipts to the SP and the SP signs receipts to the AP
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Everyone is happy!Everyone is happy!
Roaming users have consumed service
The AP has gained the valuable receipts of the SP
The SP helped a member of his area and paid off his debt
Roaming users have consumed service
The AP has gained the valuable receipts of the SP
The SP helped a member of his area and paid off his debt
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SimulationsSimulations
Input Parameters Server Repository Size Client Repository Size Users Number
Areas Number Area Population
Roaming probability Number of stay rounds in
the foreign area(stop over rounds)
Contribution of the super peers to IND
Number of super peers per area
Input Parameters Server Repository Size Client Repository Size Users Number
Areas Number Area Population
Roaming probability Number of stay rounds in
the foreign area(stop over rounds)
Contribution of the super peers to IND
Number of super peers per area
Output Parameters SW Hit Ratio Requests to the super
peers Super peers
guarantees
Output Parameters SW Hit Ratio Requests to the super
peers Super peers
guarantees
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Number of Regions EffectNumber of Regions Effect
Number of Regions effect on Hit ratio
0%10%20%30%40%50%
60%70%80%90%
100%
0 2 4 6 8 10 12 14 16 18 20 22
Number of Regions
Ave
rag
e H
it r
atio
NORMAL
ROAMERS
NORMAL w ith Super Peers
ROAMERS w ith Super Peers
Input Parameters
Patience=20 (rounds)
Server Repository Size=2000 (receipts)
Client Repository Size=300 (receipts)
Number of peers=1000 (2x500 - 4x250 - 8x125 - 10x1000 - 20x50)
Roaming Start Round=5
Roaming Probability p=0.1
Stop Over Rounds=1
Super peers Participation=80% consumer part. - 20% provider part.
Super Peers per Region=1
Number of Regions effect on SW
0123456789
10
0 2 4 6 8 10 12 14 16 18 20 22
Number of Regions
Ave
rag
e S
W p
er M
atch
NORMAL
ROAMERS
NORMAL w ith Super Peers
ROAMERS w ith Super Peers
15
Server Repository Size EffectServer Repository Size Effect
Server Repository Size effect on Hit Ratio
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
1000
1250
1500
1750
2000
2250
2500
2750
3000
Server Repository Size (receipts)
Ave
rag
e H
it r
atio
NORMAL
ROAMERS
NORMAL w ith Super Peers
ROAMERS w ith Super Peers
Server Repository Size effect on SW
0
1
2
3
4
5
6
7
8
9
10
1000
1250
1500
1750
2000
2250
2500
2750
3000
Server Repository Size (receipts)
Ave
rag
e S
W p
er M
atch
NORMAL
ROAMERS
NORMAL w ith Super Peers
ROAMERS w ith Super Peers
Input Parameters
Patience=20(rounds)
Server Repository Size=1000 (250) 3000
Client Repository Size=250
Number of peers=1000 (4x250)
Roaming Start Round=5
Roaming Probability p=0.1
Stop Over Rounds=1
Super peers Participation=80% consumer part. - 20% provider part.
Super Peers per Region=1
Server Repository size effect on Super Peers Usage
0%
20%
40%
60%
80%
100%
0 500 1000 1500 2000 2500 3000 3500
Server Repository Size (receipts)
ratio
(%)
Super peers requests
Super peers help
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Participations of super peers in the IND result
Participations of super peers in the IND result
Input Parameters
Patience = 20 (rounds)
Repository size = 2000 (receipts)
Receipts to merge = 300
Number of Peers = 1000 ( 4x250) - (20x50)
Roaming Start Round = 25
Roaming Probability p = 0.1
Stop Over Rounds = 1
super peers participation=variable
Super Peers per Region = 1
Home Super Peer Participation effect on SW
0
2
4
6
8
10
0% 20% 40% 60% 80% 100%
Home SP Participation
Ave
rag
e S
W p
er M
atch
NORMAL ROAMERS
Home Super Peer Participation Effect on Hit Ratio
95%
96%
97%
98%
99%
100%
0% 20% 40% 60% 80% 100%
Home SP participation
Ave
rag
e re
qu
est/
con
sum
e ra
tio
%
NORMAL w ith Super Peers
ROAMERS w ith Super Peers
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The effect of the number of super peers per region
The effect of the number of super peers per region
Input Parameters
Patience = 5 (rounds)
Repository size = 500 (receipts)
Receipts to merge = 100
Number of Peers = 1000 ( 8x125)
Roaming Start Round = 1
Roaming Probability p = 0.1
Stop Over Rounds = 1
super peers participation (Home - Visited)=80% - 20%
Super Peers per Region = 1,2,3
Super Peers per Region effect on SW
0
2
4
6
8
10
0 1 2 3 4
Super Peers Per Region
Ave
rag
e S
W p
er M
atch
NORMAL ROAMERS
Super Peers per Region Effect on Hit Ratio
80%
85%
90%
95%
100%
0 1 2 3 4
Super Peers Per Region
Ave
rag
e H
it r
atio
NORMAL w ith Super Peers
ROAMERS w ith Super Peers
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Scale EffectScale Effect
Scale effect on Hit Ratio
50%
60%
70%
80%
90%
100%
0 2000 4000 6000 8000
Number of Peers
Ave
rag
e H
it R
atio
Series1 Series2
Scale Effect on SW
0
2
4
6
8
10
0 2000 4000 6000 8000
Number of Peers
Ave
rag
e S
W p
er M
atch
Series1 Series2
Input Parameters
Patience = 20 (rounds)
Repository size = 1500 (receipts)
Receipts to merge = 250
Number of Peers = (4x250) (10x250) (20x250) (28X250)
Roaming Start Round = 1
Roaming Probability p = 0.1
Stop Over Rounds = 2
super peers participation (Home - Visited)=80% - 20%
Super Peers per Region = 1