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ISBN: 978-972-8939-25-0 © 2010 IADISattacks, where radio interference attacks may happen to confuse transmissions or malicious colluded nodescan attack the entire network by indefinitely flooding useless broadcasts.This work focuses on the possibility of system nodes which can eventually be used selfishly to profitmore network resources without collaborating with its own resources.We assume that a P2MAN node knows how to measure its internal state and so its health.4. EVALUATIONIn this Section we assess the performance of our approach, describing the results of simulations that showthat our variant of Network of Favors avoid that rogue peers lead the P2MAN system to collapse.4.1 Simulation ScenarioWe have performed simulations using MANET typical scenarios, in the Network Simulator 2.34. We modela network with 100 homogeneous mobile nodes. In our model, it is possible to tuning the penalty period, thenumber of rogue peers which try to send bogus pieces, and the number of free riders. For each scenario andconfiguration, results are represented by the average over ten rounds, considering a 95% confidence interval.Nodes are randomly spread over the terrain and they move around according to Random Waypoint mobilitymodel (excluding minimum speed of zero). Shared contents are sliced into pieces of 1000 Bytes, followingthe recommendations of Lee et al. (2002) regarding packet sizes. The content size is 100 KBytes.We have considered 70 downloading nodes. 25 nodes as free riders, 25 nodes are rogue peers and 20 arehonest nodes. Table shows the configured P2MAN parameters. We have setθ to be high, since a low valuemay disturb the effective download rate from honest peers and difficult the results interpretation.Table 2. P2MAN Simulation parametersParameterDescriptionSimulator NS-2 Release 2.34Number of Rounds 10Terrain Size1000x1000Mobility ModelRandom WaypointPause Time0 sRadio Range250 mBandwidth2 MbpsMAC Protocol802.11 DCF ModeMobility Maximum Speed5 m/sContent Piece Size1000 BytesContent Size100 KBytesPenalty Period300 sNumber of Nodes 100Number of Owner Nodes 30Number of Requesting Nodes 70Number of Free Riders (i.e., which do not collaborate) 25Number of Rogue Peers (i.e., which send bogus data) 25Number of Honest Nodes (i.e., collaborators) 20Health Threshold (θ ) 0.8When the simulation begins all nodes have zero favors and, at some point, requesting nodes (i.e., honest,free riders, and rogue peers) start the content discovery process. When the first honest nodes perform contentrequests, owner nodes respond with replies, if their healths are sufficient. Hence, healthy and authorizedowner nodes start to send pieces to the requesting nodes. By receiving pieces, each request node increment itsrespective owner nodes’ reputation entry in table.Similarly, when the first free riders perform content requests, healthy owner nodes also respond withreplies, due to the impossibility to determine which nodes are free rider, before a set of interactions. Hence,the expected result is which both honest peers and free riders get content pieces in the first interactions, and224