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Exploiting super peers for large-scale peer-to-peer Wi-Fi roaming

Exploiting super peers for large-scale peer-to-peer Wi-Fi roaming. Efstratios G. Dimopoulos , Pantelis A. Frangoudis and George.C.Polyzos. Motivation. Very high Wi-Fi density in cities The case for Skyhook Residential Wi-Fi hotspots with excess capacity

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Exploiting super peers for large-scale peer-to-peer Wi-Fi roaming

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  1. Exploiting super peers for large-scale peer-to-peer Wi-Fi roaming Efstratios G. Dimopoulos, Pantelis A. Frangoudis and George.C.Polyzos

  2. Motivation • 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?

  3. Design options Centralized • Permanent IDs • Full view of transactions • Easy to detect misuse FON • Decentralized • Free/disposable IDs • Enhances privacy • Should discourage misuse • Our approach

  4. Our 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

  5. Entities • Peer: provides service via home AP, consumes when mobile • Peer ID: uncertified public/private key pair • Accounting unit: digital receipt • Signed by roaming user • Proof of transaction • Receipt repositories

  6. Contributor Public Key Consuming member Certificate Timestamp Weight (amount of bytes relayed) Member Signature (Signed with member private key) Receipts and the reciprocity algorithm • 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

  7. Can it scale?

  8. The locality of visits • Visits to foreign areas are rare • IND≈0 • Receipts are unvalued in foreign areas

  9. A Super-Peer-assisted architecture • At least one Super Peer per Area • Super Peers: • Globally known • Trusted • Without extra computational capabilities

  10. An algorithm forlarge-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

  11. Example • VSP calculates: • The finalIND for the prospective consumer. • 0,2xIND (VSP) + 0,8xIND(HSP) • The guarantorSP for this transaction. 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 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 He asks service from an AP and informs the AP about the SP of his home area 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 Informs the HSP (guarantor) and the Team Server of the provider about the IND calculated Simultaneously asks from the user’s home location SP to calculate the same quantity and the waits for the answer. Informs the VSP for the calculated IND A user visits a foreign area

  12. Everyone is happy! • Roaming users have consumed service • TheAP has gainedthe valuable receipts of the SP • The SP helped a member of his area and paid off his debt

  13. Simulations • 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

  14. Number of Regions Effect

  15. Server Repository Size Effect

  16. Participations of super peers in the IND result

  17. The effect of the number of super peers per region

  18. Scale Effect

  19. THEEND Thank you!

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