WWW/Internet - Portal do Software Público Brasileiro

IADIS International Conference WWW/Internet 2010DISCOURAGING ROGUE PEERS IN A MULTICASTCONTENT DISTRIBUTION PROTOCOL FOR MANETSSidney Doria and Marco Aurélio SpohnFederal University of Campina GrandeAv. Aprígio Veloso, 882, Bodocongó, Paraíba-PB, BrazilABSTRACTRogue peers are a concern because they decrease the utility of the resource-sharing systems, potentially towards to thesystem collapse. We are currently deploying Peer-to-MANET, a multicast peer-to-peer approach to distribute contents onmobile ad hoc networks. This work presents our efforts to improve trust and fairness, avoiding rogue and selfish peers, inPeer-to-MANET. We employ a modified version of the Network of Favors as a decentralized reputation system to punishrogue peers activities. Through simulations in NS-2, we show that our solution minimizes download success rate byrogue peers and avoid that maliciously peers cause resource depletion of other peers.KEYWORDSInternet, Peer-to-Peer Networks, MANETs, BitTorrent, multicast, Reputation Systems.1. INTRODUCTIONInternet is currently defined as a global group of interconnected networks (e.g., domestic, corporative).Recently, users are become more empowered by mobile technology advances and increasing availability ofmobile services, in such a way that the usage pattern is varying and some might envision a future whereInternet will be ubiquitous by the interconnection of many mobile networks. In this path, cellular systems andmobile networks are supposed to be the future of infrastructure (Stuckmann & Zimmermann, 2009).A mobile ad hoc network (MANET) consists on a set of peers which want to get connected wirelessly butwithout relying on any fixed communication infrastructure. The mobile nature of nodes imply that they mightact as routers to others when communicating peers are two or more hops distant from each other. One can saythat most applications running on a MANET are essentially peer-to-peer (P2P) by nature. Probably the mosttargeted problem in P2P networks concerns the content distribution among peers. Recent works show effortsto adapt popular P2P protocols, especially BitTorrent (Cohen, 2003), to share data on MANETs. AlthoughBitTorrent and other protocols are known for their efficiency and popularity on the Internet, they have a setof drawbacks when running on MANETs. P2P protocols usually work in the application layer, applyingunicast transmissions, with no concerns to node mobility. On the other hand, MANETs usually make use ofunreliable broadcasts over a shared radio channel, while nodes are let to move freely. These contrasts havechallenged the research on optimizing P2P networks over MANETs.We are currently deploying Peer-to-MANET (P2MAN) (Doria & Spohn, 2009), a multicast P2P protocolfor content distribution on MANETs. The novelty of P2MAN is its holistic approach, addressing manyMANETs problems (e.g., dynamic environment, unreliable transmissions, multi-hop packet forwarding,content localization) and at the same time trying to profit from MANETs’ peculiarities (e.g., multicast meshrouting, shared radio transmissions). We have found that P2MAN is scalable and efficient on MANETs andthe preliminary performance results are encouraging.Despite the potential benefits of P2P systems like P2MAN, rogue peers are a concern because theydecrease the system utility, potentially towards to the collapse. This paper addresses the problem ofdiscouraging rogue peers activities that slow down the data distribution process by: (a) flooding other peerswith bogus data, (b) performing free riding. We propose a variant of the Network of Favors (NoF) (Andradeet al., 2004), which was originally designed to P2P CPU-sharing grids, as a decentralized reputation scheme219