the commit protocol for truthful and cost-efficient routing in ad hoc networks with selfish nodes

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The COMMIT Protocol for Truthful and Cost-Efficient Routing in Ad Hoc Networks with Selfish Nodes

Eunyoung Chang

CS 6204 Mobile Computing

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Outline

Problem Proposed Approaches COMMIT Approaches THE SYSTEM MODEL The COMMIT Protocol Protocol Analysis The Cost of Cooperation

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OBJECTIVE

Problem- In ad hoc network, establish a route for sending

packets between a Sender and Destination- rational selfish Nodes , maximize their own utility.

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Proposed Approaches

Proposed Approaches 1. Ad Hoc-VCG : based on momentary transfer - energy-efficient, truthful

2. CORSAC : route discovery and packet forward cooperation-optimal

- utility maximizing - Problem The source cannot act strategically The number of messages must be exchanged

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COMMIT Approach

COMMIT Routing Protocol Goal 1. individual rationality 2. Truthfulness 3. The most energy-efficient(least Cost) path. 4. The message complexity is low.

COMMIT Protocol - COMMIT : Sender-centric, incentive-compatible

routing protocols

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COMMIT Protocol

Protocol

Truth. Routers

Truth. Forward

Strategic sender

Message Complex

Ad Hoc-VCG

Yes Partially No O(n3)

CORSAC Yes Yes No O(n3)

COMMIT Yes Partially

Yes O(|M|2d)

<Main Features of Routing Protocols>

• The major difference - The costs of routing are relative with nodes, not links.

- periodic topology control protocol- Game theory simple- Message complexity low

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THE SYSTEM MODEL

• Network Model - n nodes

- Links in the communication graph G.- Symmetric wireless link- 2-connected - topology control protocol

- K-Neigh, CBTC, CTR • Modeling routing as a Game : D, S, Relay nodes,

- D : “neural referee” - S : private information (type) , us = m - cs(D)

(u: utility of S, m: maximum per-packet price, cs(D):actual per-packet price ) - R : Cv = l(v) , us = pay(v) – l(v)

(l(v) : power level, Cv : cost to relay a packet, pay(v) : per-packet payment)

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THE SYSTEM MODEL

• Strategy Game – truth telling 1. A node can declare any type. 2. Drop control messages 3. Modify messages 4. Create bogus messages

• The Goal- Route message with the most efficient paths

• The features- truthful, incentive compatible, strategy proof

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The COMMIT Protocol

1. The mechanism 1. Winner determination by D 2. Payment computation by D 3. Billing.

2. The pricing scheme

3. Protocol Specification

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The COMMIT Protocol

2. The Pricing Scheme : Determine cs(D) ?

c(P) : The energy cost of a path P between S/D c(P) = ∑vЄP, v Є {S,D} l(v) MP : The wining path = {v1, v2, v3}

<replacement path> P-v : the path that does not include v c(P-v) : the cost of the minimum energy (S,D) path P-v

` pay(v) : Payment for a node v in the wining path MPpay(v) = c(P-v) – c(MP) +l(v)pay(v) = 0 ( for the nodes, that are not on the wining

path)

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2020

(S,D,20)

S D

v1

v2

v3

v5v4

51

m = 65

l

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The COMMIT Protocol2. The Pricing Scheme : Determine cs(D)

(Q. Would the communication take place in the nodes?)

m = 65

(A. If truthfully, The communication would NOT take place)

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20

2020

(S,D,20)S D

v1v3

v4 v5

v2

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v2

MP (The wining path) = {v1, v2, v3} = 26c(P-v1) (Replacement path ) = {v4 v5 } = 40 = c(P-v2) = c(P-v3) pay(v1) = c(P-v1) – c (MP) +l(v1) = 40 – 26 + 5 = 19, pay(v2)= 34, pay(v3) = 15 pay(v1) + pay(v2) + pay(v3) = 68 > 65

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20

2020

(S,D,20)S D

v1v3

v4 v5 m = 65

Utility for all the players = 0

(A. The communication would not take place)

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v2

But assume that node V2 falsely declares power level 30 ? pay(v1) + pay(v2) + pay(v3) = 48 < 65

Utility of v2 : 34 – 20 = 14.

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30

2020

(S,D,20)S D

v1v3

v4 v5 m = 65

(The communication would take place)(V2 would increase its utility)

Therefore, cs(D) = ∑vЄP, v Є {S,D} pay(v) would result in a nontruthful mechanism

l

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v2

But assume that node V2 falsely declares power level 30 ? pay(v1) + pay(v2) + pay(v3) = 48 < 65

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20

2020

(S,D,20)S D

v1v3

v4 v5 m = 65

In order to circumvent this problem : cs(D) = c(P-mp) = 40c(P-mp) : global replacement pathcs(D) < m : feasible

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The COMMIT Protocol

2. The Pricing Scheme : Determine cs(D) - feasible : protecting the condition individual rationality.

c(P-mp) ≠ ∑ pay(v) : budget is

imbalanced

<Case 2 > c(P-mp) > ∑ pay(v) : getting additional money

by D

c(P-mp) < ∑ pay(v) : Contributing to the payment by D

vЄP, v Є {S,D} l

vЄP, v Є {S,D} l

vЄP, v Є {S,D} l

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The COMMIT Protocol

3. Protocol Specification1. Route discovery

S : RD (S, D, m) using l(S)R : RD (S, D, m, v1,l(v1),…, vk-1,l(vk-1)) , Vk build up

local view D : RD (S, v1, v2,…, vk-1, vk, D) from S to D , P-vi , P-mp

MP feasible(cs(D) = c(P-mp) < m)

2. Data transition: (only if MP is feasible) start : along the winning path MP from S to D

end : last packet of S, changes topology control protocol

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The COMMIT Protocol

- Truthful route discovery imply truthful data forwarding?

<Optimization > 1. forward only new edges : reduces the message complexity phase. 2. Vk compute whether a newly received path is

feasible -

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Protocol Analysis

1. Energy Efficiency : If truthfully, COMMIT computes MP

2. Message Complexity

S D

M

n1

n1

d

d

d d Each node forwards to |M| n1 forwards to |M| * degree d n1 has complete |M|dEach node |M| repeats ‘same’

Thus, |M|(|M|d)

3. Truthfulness and Individual Rationality : S, R, D

(The subset of all relay nodes)

(the maximum node

degree)

d

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Protocol Analysis – S

3. Truthfulness and Individual Rationality - prove : for the sender Sender : S will never pay a price that exceeds m.

1. mf < m :

a. C(P-mp) < mf < m : the utility remains the same. b. mf < C(P-mp) < m : the communication would not

takes place. c. C(P-mp) < mf < m : declaring utility unchanged at

zero .

2. mf > m : along the same line of case 1 above.

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Protocol Analysis – R

3. Truthfulness and Individual Rationality : S, R, D - prove : the Relay nodes A relay node : will never get a negative utility when acting

truthfully.

- Analyze the different cheating behaviors of the rely node

: An relay node v could 1 . lie about its type (power level l(v)) 2. Propagate a path with false information

3. internationally fail to propagate a path with new information

4. combine the above possibilities

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3. Truthfulness and Individual Rationality : S, R, D 1. lie about its type (power level l(v)) : Utility

unchanged - Cheating option 1 : l(v) , lf(v) a . l(v) < lf(v) : b . l(v) > lf(v) :

.

30

2020

(S,D,20)

S D

v1

v2

v3

v5v4

51

m = 65

if vЄMP

No effect on the decision rule

10

2020

(S,D,20)

S D

v1

v2

v3

v5v4

51

m = 65

if vЄMP

v’s utility would not be changed

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3. Truthfulness and Individual Rationality : S, R, D 2. Propagate a path with false information : case - Creating a false neighbor

take : RD(S,D, m, v1,, l(v1) ,…, vi-1, l(vi-1) ) forward: RD(S,D, m, v1,, l(v1) ,…, vi-h, l(vi-h), v, l(v) )

1. v is in the MP, feasible 2. v is in the MP, Not feasible

3. v is not in the MP, but it is in the (false) minimum-energy MP

- Creating a false overhop path forward: RD(S,D, m, v1,, l(v1) ,…, vi-h, l(vi-h), v, l(v) ) 1. v is in the MP, feasible

2. v is in the MP, Not feasible 3. v is not in the MP.

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3. Truthfulness and Individual Rationality : S, R, D 2. Propagation with false info – 1) creating a false

neighbor Case: 1. v is in the MP, which is feasible : e’ = (vi-h , v )

uv = c(P-v) – c(MP) utility cost ↑, the cost of false MPf ↓ by e’e’ ∈ MPf

But e’ does not exist in G Payments during data session : zero

S D

v1

v

v3

v5v4

e’

reduce utility

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neighbor Case: 2. v is in the MP, which is NOT feasible : e’ = (vi-h , v )

utility zero

2

S D

v1

v

v3

v5v4

e’

utility cost ↑, the cost of P-mp ↓ by e’Not belong to P-mp

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neighbor Case: 3. v is not in the MP, but it is in the (false) minimum-energy MP : e’ = (vi-h , v )

S D

v1

v2

v3

vv4

utility zero

e’ ∈ MPf

e’ does not exist in G Payments during data session : zeroe’

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3. Truthfulness and Individual Rationality : S, R, D 2. Propagation with false info – 2) Creating a false

overhop Path Case: 1. v is in the MP, which is feasible : e’ = (vi-h , vi+1 )

S D

v1

v2

v3

v5v4

e’

reduce utility

uv = c(P-v) – c(MP) The c(P-v) ↓ while cost of MP unchanged by e’

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overhop Path Case: 2. v is in the MP, which is NOT feasible : e’ = (vi-h , vi+1 )

Data session would be aborted

S D

v1

v2

v3

v5v4

utility cost ↑, the cost of false MPf ↓ by e’However, test Msg along global replacement pathe’ does not exist in G

e’

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overhop Path Case: 3. v is not in the MP : e’ = (vi-h , vi+1 )

S D

v1

v2

v3

v5v4

e’

utility zero

Not on the end point of e’ Leave v out of MP by e’

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3. Truthfulness and Individual Rationality : S, R, D 3. Intentionally fail to propagate with new info

Case: 1. v is in the MP, which is feasible

S D

v1

v2

v3

v5v4

no incentive in not reporting edge info

uv = c(P-v) – c(MP) utility cost ↓ , the cost of MP↑ by no reporting

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Case: 2. v is in the MP, which is NOT feasible

no incentive in not reporting

S D

v1

v2

v3

v5v4

No way utility cost ↑

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Case: 3. v is not in the MP and try to join the MP by not reporting one of the edges e

S D

v1

v2

v3

v5v4

utility zero

c(MP) > c(MP v)c(MP v) ↑ by no reporting no way for v to turn MP v into the MP

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3. Truthfulness and Individual Rationality 4. combine the above possibilities

S D

v1

v2

v3

v5v4

utility zero

No way utility cost ↑

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Protocol Analysis – D

3. Truthfulness and Individual Rationality : S, R, D 3. D acts truthfully

- Interest : receive data, new connection, customers happy

- No interest : Sender pay less, R’s overpayment

Thus If COMMIT executes in ad hoc, truthfulness is strategy

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The Cost of Cooperation

The cost of cooperation : The Difference between premium and MP

cost : The measure of inefficiency (C(MP) < m)

but c(P-mp) > m ; communication aborted

- COMMIT Approach : changing the topology of the new network.

the commit protocol for truthful and cost-efficient routing in ad hoc networks with selfish nodes

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