1. Self-Organized Aggregation of Wi-Fi Networks Elias C. Efstathiou, Advisor: George C. Polyzos Mobile Multimedia Laboratory, Department of Computer Science Athens University of Economics and Business Abstract: We present a peer-to-peer (P2P) scheme that could fuel the deployment of free public wireless networks in cities; we call it P2P Wireless Network Confederation (P2PWNC). Unlike existing approaches, P2PWNC does not rely on central planning. In P2PWNC, wireless service is provided to those who provide service to others based on an algorithm that runs in isolation on every peer. 1 Private Wi-Fi networks, connected to the Internet, cover major metropolitan areas We could use one another’s networks to access the Internet Plus, Wi-Fi phones are now available Motorola CN620 2 How to encourage Wi-Fi connection sharing? – “Give to those who give” Design a reciprocity scheme that is – fully self organized – collusion proof – easy to join 3 Participants form small teams, typical teams = households Team IDs are uncertified, no need for authorities Teams operate one or more Wi-Fi access points (APs) Team members sign receipts whenever they access another team’s APs Motivation The Problem Solution Architecture 4 1 1All IDs = unique public/private key (PK/SK) pairs 2 2 Member certificate: 3 3Receipt: 4 4Decision function: Receipt Graph, When to Cooperate? 5 Teams have partial view of receipt graph Teams do not cooperate in a distributed storage scheme and there is no central repository of receipts Must rely on members to disseminate receipts: – members carry a subset of the receipts their team knows about – before requesting service, members transmit these receipts to the prospective provider 6 Assume cost c when providing a unit of service and benefit b when receiving one For various b/c ratios (>1): – let each team follow one of various predefined sharing strategies – let teams interact at random – allow teams to learn, i.e. switch to better-performing strategies When do cooperative strategies outperform non-cooperative ones? Example of a conditionally cooperative strategy from [2] (black) outperforming “never share” (blue) and “always share” (red) 7 Incomplete Information Evolutionary Learning Framework Protocol, Implementation 8 We design, simulate, and implement [2, 3, 4, 5] a self-managed solution for Wi-Fi aggregation, which can be deployed spontaneously Additional information: the Peer-to-Peer Wireless Network Confederation section at http://mm.aueb.gr/research/ and via e-mail to efstath@aueb.gr (Elias Efstathiou) [1] Feldman, Lai, Stoica, Chuang, Robust Incentive Techniques for Peer-to-Peer Networks, Proc. ACM EC’04. [2] Efstathiou, Polyzos, Self-Organized Peering of Wireless LAN Hotspots, European Transactions on Telecommunications (special issue on Self-Organization in Mobile Networking, in press). [3] Efstathiou, Frangoudis, Polyzos, in preparation. [4] Antoniadis, Courcoubetis, Efstathiou, Polyzos, Strulo, Peer-to-Peer Wireless LAN Consortia: Economic Modelling and Architecture, Proc. IEEE P2P’03. [5] Efstathiou, Polyzos, A Peer-to-Peer Approach to Wireless LAN Roaming, Proc. ACM MobiCom WMASH’03. Summary, Contact, References Simple text-based protocol [3]: – CONN: Client requests service from access point (AP) (request includes member certificate) – CACK: Positive/negative response from AP – RREQ: AP requests an updated receipt for the current session (thus splitting consumer/provider risk) – RCPT: Client transmits a stored or a newly signed receipt – UPDT: Client requests latest receipts from own team Wi-Fi network view Team view : Wi-Fi access point : team member White team Green team Blue team White team PK Green member cert Signed by Green member SK Green team AP: “Should I cooperate with the member from the Blue team who is requesting service?” B W G Y X Z Timestamp Weight timestamp volume of traffic member PK team PK signed by team SK providing team PK consumer cert. signed by consumer SK timestamp volume of traffic 5 5 consult receipt graph: receipt graph contains the community’s history graph arrows encode the owes to relationship we study collusion-proof reciprocity strategies [1] that allow the evolution of cooperation ? 6 AP code runs on the Linux-based Linksys WRT54GS AP Keys and certificates based on Elliptic Curve Cryptography (Receipt size: 150 bytes)