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Peer-to-Peer Wireless Network Confederation (P2PWNC) George C. Polyzos Mobile Multimedia Laboratory Department of Computer Science Athens University of Economics and Business http://mm.aueb.gr/ P2P colloquium, Darmstadt, December 7, 2005 [email protected] Idea A wireless LAN (WLAN) aggregation scheme Unites WLANs in citywide [con]federations Requires no authorities: open to all, IDs are free Relies on reciprocity between peers Motivation Numerous WLANs, connected to the Internet, are within the range of passersby Manhattan WLANs, 2002 Skyhook Wireless Wi-Fi Positioning System (WPS) [email protected] Motivation Motivation (II) Many WLANs are secured against outsiders Need incentives to keep them open Motivation (III) WLAN-enabled mobile phones are on the market Motivation (IV) Public WLAN operators mainly target “hotspots” Municipal wireless still in its infancy [email protected] Motorola CN620 Nokia 9500 The Public Hotspot Market From Gartner: 2001: 1200 public hotspots worldwide 2003: 71 000 public hotspots worldwide 2005: 23 500 WLANs in hotels worldwide A subscription buys you (June 2005): Sprint PCS: 19 000 hotspots worldwide Boingo Wireless: 17 400 hotspots worldwide T-Mobile HotSpot: 16 663 hotspots worldwide Skyhook Wireless data (2005): [email protected] 50 000 WLANs in just 5 Massachusetts cities and towns (Watertown, Brookline, Roxbury, Newton, and Cambridge) The Rules P2PWNC: An incentives-based P2P system Teams provide WLAN access to each other Teams should provide in order to consume Blue team White team Green team : WLAN access point : team member [email protected] WLAN view Team view N-way Exchanges Adopt N-way exchanges as the incentive scheme A generalization of barter, which retains some of its simplicity “Provide to those [who provided to those]* who provided to me” A type of (cyclical) indirect reciprocity Scales to larger communities, compared to direct-only exchanges Does not rely on (central or distributed) authorities A B C D Some variants of the basic N-way scheme: Cox, Noble, “Samsara: Honor Among Thieves in P2P Storage,” SOSP’03 Ngan, Wallach, Druschel, “Enforcing Fair Sharing of P2P Resources, “ IPTPS’03 Anagnostakis, Greenwald, “Exchange-based Incentive Mechanisms for P2P File Sharing,” ICDCS’04 Feldman, Lai, Stoica, Chuang, “Robust Incentive Techniques for P2P Networks,” ACM EC’04 [email protected] Versions Architecture Version 1.0 (MMAPPS) Incentive technique Comment MMAPPS local accounts pattern Relied on tamperproof software NWAY1 Favors large teams, unimplemented Version 2.0 GMF2 Assumes homogeneous consumptions Version 3.0 (in progress) in progress More realistic assumptions 1. E. C. Efstathiou and G. C. Polyzos, “Self-Organized Peering of Wireless LAN Hotspots,” European Transactions on Telecommunications, vol. 16, no. 5, (Special Issue on Self-Organization in Mobile Networking), Sept/Oct. 2005. [12% acceptance rate] 2. E. C. Efstathiou, P. A. Frangoudis, and G. C. Polyzos, “Stimulating Participation in Wireless Community Networks,” IEEE INFOCOM 2006, Barcelona, Spain, April 2006 (to appear). [18% acceptance rate] [email protected] Version History Sept. 2002: P2PWNC started in the context of IST MMAPPS (Market Management of Peer-to-Peer Services) Sept. 2003: Demo of version 1.0 Team 1 (5 persons from AUEB) Theory Team (2 persons from AUEB) June 2005: Demo of version 2.0 Team 2 (3 persons) Results will be presented at IEEE INFOCOM, Barcelona, April 2006 Oct. 2005: Started work on version 3.0 Team 3 (7 persons) Preparing demo for TRIDENTCOM 2006 and/or INFOCOM 2006 [email protected] System Entities Team = Members + Access Points (APs) Teams := P2PWNC peers Assume intra-team trust Team ID = (unique) PK-SK pair PK: public key SK: private key Member certificate Member ID = (unique) PK-SK pair Member certificate binds Member PK to Team PK Receipt Encodes P2PWNC transactions between teams Signed by consuming member Receipt weight: amount of bytes the AP forwarded [email protected] Member PK Team PK Signed by Team SK Team PK Member cert Timestamp Weight Signed by Member SK Receipt Generation 11:50am = t0 (member connects) 11:51am (P requests 1st receipt) CONN RREQ C P C P CACK RCPT RCPT timestamp = t0 RCPT weight = w1 11:52am (P requests 2nd receipt) 11:53am (member has departed) RREQ C P RCPT RCPT timestamp = t0 RCPT weight = w2 > w1 [email protected] RREQ (timeout) Receipt Repository P RCPT P stores last receipt P2PWNC Protocol: Entities and Messages Access Point Mobile User Repository CONN QUER CACK QRSP RREQ RCPT RREQ Timeout/ Conn. closed RCPT P2PWNC/2.0 Content-length: 357 Algorithm: ECC160 Timestamp: Tue, 24 May 2005 17:26:41 +0000 Weight: 6336 BNibmxStfJlod/LnZubH6pzWHQqKyZFcSMjnZurmTe4KjCRkllhV93MEegPv Csxz2oe/hqevoPSrwO1JLO/36J8HTIeyeKQqTCfx+EPxweAvYC/ZFb8URLa2 faIbvSgD3lm6Wa1S4cYlSWeSNmFzS/ebDFfzakqNSEsERefwEcdWJD9gzIXa fL4pojhhfP5brS4QPtHzBl58POfKdx9AqCDMBxRoGALKJSJYYXlsrwtiyZJK vPlU5B3lWrFuL25Pd+kv2iMVRElXk/4= RCPT Text-based protocol. Certificates and keys encoded in Base64. [email protected] Centralized Operation Mode One RR (Receipt Repository) for all teams. - Susceptible to DoS in layer 3 and in app. layer (overflow RR with fake receipts) - Confederation teams may be unable or unwilling to agree on the same RR, dividing the confederation + Simpler to deploy and bootstrap [email protected] Decentralized Operation Mode One RR (Receipt Repository) per team (running on the “team server”). + Not susceptible to DoS (IP address known only within the team) and only team members talk to it - Needs gossiping mechanism (which uses the members themselves to carry receipts around) - Partial views of confederation history can favor free-riding [email protected] The Receipt Graph Directed weighted graph (with cycles) W1 E F W2 W5 Graph security W4 W3 B W6 W9 W7 A Free-riders and colluders can create an arbitrary number of fake vertices and edges G W14 I W8 W13 W10 W11 D C H They cannot create fake outgoing edges starting from teams who are outside the colluding group (they do not have the relevant private keys) W12 Vertices: team public keys Edge weight: sum of weights of corresponding receipts Edges point from the consuming team to the providing team [email protected] GMF - Background Directed weighted graph (with cycles) W1 E F W2 W5 Graph security W4 W3 B W6 W9 W7 A Free-riders and colluders can create an arbitrary number of fake vertices and edges G W14 I W8 W13 W10 W11 D C H They cannot create fake outgoing edges starting from teams who are outside the colluding group (they do not have the relevant private keys) W12 Vertices: team public keys Edge weight: sum of weights of corresponding receipts Edges point from the consuming team to the providing team [email protected] GMF - Heuristic Directed weighted graph (with cycles) W1 E F W2 W5 Graph security W4 W3 B W6 W9 W7 A Free-riders and colluders can create an arbitrary number of fake vertices and edges G W14 I W8 W13 W10 W11 D C H They cannot create fake outgoing edges starting from teams who are outside the colluding group (they do not have the relevant private keys) W12 Vertices: team public keys Edge weight: sum of weights of corresponding receipts Edges point from the consuming team to the providing team [email protected] GMF - Evaluation Directed weighted graph (with cycles) W1 E F W2 W5 Graph security W4 W3 B W6 W9 W7 A Free-riders and colluders can create an arbitrary number of fake vertices and edges G W14 I W8 W13 W10 W11 D C H They cannot create fake outgoing edges starting from teams who are outside the colluding group (they do not have the relevant private keys) W12 Vertices: team public keys Edge weight: sum of weights of corresponding receipts Edges point from the consuming team to the providing team [email protected] [email protected] [email protected] IST MMAPPS version (Version 1.0) P2PWNC Domain Agent Application WLAN events WLAN service calls WLAN Provisioning Service [email protected] Network Services MMAPPS and JXTA Firewall Packet sniffer Negotiation DHCP Routing / NAT Rate control Authentication Accounting Rules IST MMAPPS version (Version 1.0) 1. Visitor credentials check WLAN WLAN (visitor password resides in home database) 6. Balance OK: Proceed Visitor Negotiation Visitor Session Visitor Negotiation 5. Start MMAPPS Negotiation 2. Negotiate Negotiation Listener 3. Request service 4a. MMAPPS negotiation MMAPPS Negotiation 4b. Balance check Visited peer - Provider [email protected] Home peer - Consumer First attempts at Linux-based WLAN mgmt: AAA, DHCP, NAT, QoS, … [email protected] First attempts at Linux-based WLAN mgmt: Traffic logging using (fast) kernel, user modules [email protected] First simple rules (tamperproof software!) [email protected] First experiments with PDAs and Linux WLAN gateways [email protected] Version 2 Architecture Receipt store GMF execution Member update (decentralized mode) Home-AP interface DHCP NAT/router/firewall Standard PC, or collocated with Linksys Authenticator Receipt verification Linksys WRT54GS AP (32MB RAM, 8MB Flash) Member-AP interface Windows Mobile client Member certificate . Receipt generation Member-Home interface [email protected] Also carries team receipts (decentralized mode) Linksys WRT54GS Linux-based WLAN access point [email protected] We implemented the P2PWNC protocol (AP side) on it 32 MB RAM, 8 MB Flash, 200 MHz CPU Retails for less than $70 Cryptographic, maxflow performance comparable to 200 MHz PC Can act as team server/RR (storing more than 10 000 receipts) Repository Implementation (Version 2.0) • Receipt Repository – Efficient, composite data structure for receipt storage and queries – Incentive algorithms: pluggable modules – maximum-flow algorithm optimizations • Push-Relabel Algorithm O(V3) • Global relabeling heuristic [email protected] Linksys verification performance compared to a 2GHz PC for all P2PWNC signature types Athlon XP 2800 Linksys WRT54GS Bit length (RSA/ECC) RSA ECC RSA ECC 1024/160 0.4 ms 6.5 ms 12.3 ms 114.7 ms 1536/192 0.8 ms 6.0 ms 21.4 ms 99.9 ms 2048/224 1.3 ms 7.1 ms 37.9 ms 135.7 ms 3072/256 2.8 ms 8.6 ms 75.3 ms 453.0 ms [email protected] QoS Scheme for version 3.0 Reinterpret the result of GMF not as probability to provide unrestricted service but as the QoS to be provided P2PWNC Team/TCA Server Abstraction Layer (AL) Linux Module MS Windows Module OS - Internet Link [email protected] Proposal Build traffic policing module for both Windows and Linuxbased (tc-based) routers Secure Services (version 3.0) Internet Home AP 1 Home AP 2 Internet Visited AP 1 Internet Team Server 1 Team Server 2 Visited AP 2 GSM Wireless Client 1 Wireless Client 2 Each client uses its own tunnel endpoint for scalability (usually their own home). Client can learn the endpoint’s current IP address from his team server. Caller sends SMS containing current tunnel endpoint IP address and a tunnel identifier. No centralized registrars are needed (e.g. SIP registrars, dynamic DNS). [email protected] L2TP IPSec Tunnels Client side support: Windows, Windows Mobile Server side support: Linux (and Linksys), Windows [email protected] NAT traversal a problem for IPSec, but: IPSEC-ESP-RFC 3948: UDP encapsulation of IPSec ESP Packets (used after a NAT detection process detects a NAT) Support for NAT-T in Windows, Windows Mobile and in the Openswan Linux VPN gateway that we are using [email protected] VoIP for Windows Mobile (version 3.0) [email protected] Deployment: the Athens Wireless Metropolitan Network [email protected] AWMN and P2PWNC AWMN is one of the largest WMNs globally, with more than 3000 nodes P2PWNC version 3.0 is designed to be compatible with most AWMN nodes Setup of AWMN Node #66 in MMlab is finally underway! [email protected] P2PWNC Publications and Website 1. E. C. Efstathiou and G. C. Polyzos, “Self-Organized Peering of Wireless LAN Hotspots,” European Transactions on Telecommunications, vol. 16, no. 5, (Special Issue on Self-Organization in Mobile Networking), Sept/Oct. 2005. [12% acceptance rate] 2. E. C. Efstathiou and G. C. Polyzos, “Peer-to-Peer Wireless Network Confederation,” in Encyclopedia of Virtual Communities and Technologies, S. Dasgupta, ed., Idea Group Reference, 2005. 3. E. C. Efstathiou and G. C. Polyzos, “P2PWNC: A Peer-to-Peer Approach to Wireless LAN Roaming,” in Handbook of Wireless Local Area Networks: Applications, Technology, Security, and Standards, M. Ilyas, S. Ahson, eds., CRC Press, 2005. 4. E. C. Efstathiou, P. A. Frangoudis, and G. C. Polyzos, “Stimulating Participation in Wireless Community Networks,” IEEE INFOCOM 2006, Barcelona, Spain, April 2006 (to appear). [18% acceptance rate] 5. P. A. Frangoudis, E. C. Efstathiou, and G. C. Polyzos, “Reducing Management Complexity through Pure Exchange Economies: A Prototype System for Next Generation Wireless/Mobile Network Operators,” 12th Workshop of the HP Openview University Association (HPOVUA), Porto, Portugal, July 2005. 6. E. C. Efstathiou and G. C. Polyzos, “Can Residential Wireless LANs Play a Role in 4G?” 4G Mobile Forum (4GMF) Annual Conference, San Diego, CA, July 2005. 7. E. C. Efstathiou and G. C. Polyzos, “A Self-Managed Scheme for Free Citywide Wi-Fi,” IEEE WoWMoM Autonomic Communications and Computing Workshop, Taormina, Italy, June 2005. 8. E. C. Efstathiou, “Self-Organized Peering of Wireless LANs,” IEEE INFOCOM 2005 Student Workshop, Miami, FL, March 2005. 9. E. C. Efstathiou and G. C. Polyzos, “Trustworthy Accounting for Wireless LAN Sharing Communities,” 1st European PKI Workshop, Samos Island, Greece, June 2004. 10. E. C. Efstathiou and G. C. Polyzos, “Designing a Peer-to-Peer Wireless Network Confederation,” IEEE LCN Workshop on Wireless Local Networks (WLN), Bonn, Germany, Oct. 2003. 11. P. Antoniadis, C. Courcoubetis, E. C. Efstathiou, G. C. Polyzos, and B. Strulo, “Peer-to-Peer Wireless LAN Consortia: Economic Modeling and Architecture,” 3rd IEEE International Conference on Peer-to-Peer Computing, Linköping, Sweden, Sept. 2003. 12. E. C. Efstathiou and G. C. Polyzos, “A Peer-to-Peer Approach to Wireless LAN Roaming,” ACM MOBICOM Workshop on Wireless Mobile Applications and Services on WLAN Hotspots (WMASH), San Diego, CA, Sept. 2003. 13. P. Antoniadis, C. Courcoubetis, E. C. Efstathiou, G. C. Polyzos, and B. Strulo, “The Case for P2P Wireless LAN Consortia,” 12th IST Summit on Mobile/Wireless Communications, Aveiro, Portugal, June 2003. http://mm.aueb.gr/research/p2pwnc/ [email protected]