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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. The COMMIT Protocol for Truthful and Cost-Efficient Routing in Ad Hoc Networks with Selfish Nodes. Outline. Problem Proposed Approaches COMMIT Approaches THE SYSTEM MODEL The COMMIT Protocol Protocol Analysis The Cost of Cooperation.

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

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  1. Eunyoung Chang CS 6204 Mobile Computing The COMMIT Protocol for Truthful and Cost-Efficient Routing in Ad Hoc Networks with Selfish Nodes

  2. Outline • Problem • Proposed Approaches • COMMIT Approaches • THE SYSTEM MODEL • The COMMIT Protocol • Protocol Analysis • The Cost of Cooperation

  3. OBJECTIVE • Problem - In ad hoc network, establish a route for sending packets between a Sender and Destination - rational selfish Nodes ,maximize their own utility.

  4. 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

  5. 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

  6. COMMIT Protocol • The major difference • - The costs of routing are relative with nodes, not links. • - periodic topology control protocol • - Game theory simple • - Message complexity low <Main Features of Routing Protocols>

  7. 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)

  8. 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

  9. 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

  10. 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, vЄ {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 MP pay(v) =c(P-v) – c(MP) +l(v) pay(v) = 0 ( for the nodes, that are not on the wining path) v4 m = 65 v5 20 20 l 1 5 (S,D,20) S D 20 v3 v1 v2

  11. The COMMIT Protocol 2. The Pricing Scheme : Determine cs(D) (Q. Would the communication take place in the nodes?) v4 v5 m = 65 20 20 (S,D,20) S D 1 5 20 v3 v1 v2 (A. If truthfully, The communication would NOT take place)

  12. The COMMIT Protocol 2. The Pricing Scheme : Determine cs(D) (Q. Would the communication take place in the nodes?) v4 v5 m = 65 20 20 (S,D,20) S D 1 5 20 v3 v1 v2 MP (The wining path) = {v1, v2, v3} = 26 c(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 (A. The communication would not take place) Utility for all the players = 0

  13. The COMMIT Protocol 2. The Pricing Scheme : Determine cs(D) (Q. Would the communication take place in the nodes?) v4 v5 m = 65 20 20 (S,D,20) S D 1 5 30 v3 v1 v2 But assume that node V2falsely declares power level 30 ? pay(v1) + pay(v2) + pay(v3) = 48 < 65 (The communication would take place) (V2would increase its utility) Utility of v2 : 34 – 20 = 14. Therefore, cs(D) = ∑vЄP, vЄ {S,D} pay(v) would result in a nontruthful mechanism l

  14. The COMMIT Protocol 2. The Pricing Scheme : Determine cs(D) (Q. Would the communication take place in the nodes?) v4 v5 m = 65 20 20 (S,D,20) S D 1 5 20 v3 v1 v2 But assume that node V2falsely declares power level 30 ? pay(v1) + pay(v2) + pay(v3) = 48 < 65 In order to circumvent this problem : cs(D) = c(P-mp) = 40 c(P-mp) : global replacement path cs(D) < m : feasible

  15. The COMMIT Protocol • 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, vЄ {S,D} l vЄP, vЄ {S,D} vЄP, vЄ {S,D} l l

  16. The COMMIT Protocol • Protocol Specification 1. 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

  17. 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

  18. Protocol Analysis 1. Energy Efficiency : If truthfully, COMMIT computes MP 2. Message Complexity d d d S D n1 d (the maximum node degree) Each node forwards to |M| n1 forwards to |M| * degree d n1 has complete |M|d Each node |M| repeats ‘same’ Thus, |M|(|M|d) d M n1 (The subset of all relay nodes) 3. Truthfulness and Individual Rationality : S, R, D

  19. 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.

  20. 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

  21. Protocol Analysis – R 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) : . v4 v4 m = 65 m = 65 v5 v5 20 20 20 20 1 1 5 5 (S,D,20) (S,D,20) S S D D 10 30 v3 v3 v1 v1 v2 v2 if vЄMP if vЄMP No effect on the decision rule v’s utility would not be changed

  22. Protocol Analysis – R 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.

  23. Protocol Analysis – R 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 ) v4 v5 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 v3 e’ v1 v reduceutility

  24. Protocol Analysis – R 3. Truthfulness and Individual Rationality : S, R, D 2.Propagation with false info – 1) creating a false neighbor Case: 2. v is in the MP, which is NOT feasible : e’ = (vi-h , v ) v4 v5 2 utility cost ↑, the cost of P-mp ↓ by e’ Not belong to P-mp S D v3 e’ v1 v utility zero

  25. Protocol Analysis – R 3. Truthfulness and Individual Rationality : S, R, D 2.Propagation with false info – 1) creating a false neighbor Case: 3. v is not in the MP, but it is in the (false) minimum-energy MP : e’ = (vi-h , v ) v4 v e’ ∈MPf e’ does not exist in G Payments during data session : zero S D e’ v3 v1 v2 utility zero

  26. Protocol Analysis – R 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) v4 v5 uv = c(P-v)– c(MP) The c(P-v)↓ while cost of MP unchanged by e’ S D e’ v3 v1 v2 reduceutility

  27. Protocol Analysis – R 3. Truthfulness and Individual Rationality : S, R, D 2.Propagation with false info – 2) Creating a false overhop Path Case: 2. v is in the MP, which is NOT feasible : e’ = (vi-h , vi+1) v4 v5 utility cost ↑, the cost of false MPf↓ by e’ However, test Msg along global replacement path e’ does not exist in G S D e’ v3 v1 v2 Data session would be aborted

  28. Protocol Analysis – R 3. Truthfulness and Individual Rationality : S, R, D 2.Propagation with false info – 2) Creating a false overhop Path Case: 3. v is not in the MP : e’ = (vi-h , vi+1) v4 v5 e’ Not on the end point of e’ Leave v out of MP by e’ S D v3 v1 v2 utility zero

  29. Protocol Analysis – R 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 v4 v5 uv = c(P-v)– c(MP) utility cost ↓ , the cost of MP↑ by no reporting S D v3 v1 v2 no incentive in not reporting edge info

  30. Protocol Analysis – R 3. Truthfulness and Individual Rationality : S, R, D 3.Intentionally fail to propagate with new info Case: 2. v is in the MP, which is NOT feasible v4 v5 No way utility cost ↑ S D v3 v1 v2 no incentive in not reporting

  31. Protocol Analysis – R 3. Truthfulness and Individual Rationality : S, R, D 3.Intentionally fail to propagate with new info Case: 3. v is not in the MP and try to join the MP by not reporting one of the edges e v4 v5 c(MP) > c(MP v) c(MP v) ↑ by no reporting no way for v to turn MP vinto the MP S D v3 v1 v2 utility zero

  32. Protocol Analysis – R 3. Truthfulness and Individual Rationality 4. combine the above possibilities v4 v5 No way utility cost ↑ S D v3 v1 v2 utility zero

  33. 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

  34. 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.

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