Browsing by Subject "Peer-to-Peer"
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Item A Packet Scheduling Mechanism for Wireless Peer-to-Peer Content Distribution(2013-11-26) Liu, YaoThis thesis studies the problem of content distribution in wireless peer-to-peer networks with selfish nodes. In this problem a group of wireless nodes need to exchange a set of files over a lossless broadcast channel. Each node aims to maximize its own download rate and minimize its upload rate. We propose a distributed protocol that provides incentives for selfish nodes to participate in the content exchange. Our protocol does not require any exchange of money and reputation and hence can be easily implemented without additional infrastructure. Then, we will analyze the performance of our protocol by focusing on the import\-ant case in which the system contains two files that need to be distributed. We derive a closed-form expression of Nash Equilibrium and characterize the corresponding system performance in discrete time. Furthermore, we propose a distributed mechanism where the strategy of each node is only based on the observed history of the system and not on the private information of other nodes. We also study the performance characteristics of the systems that employ network coding to facilitate data exchange. We show that, due to the free rider problem network coding does not necessary improve the performance of the system and, in some cases, may lead to worse system performance. We propose a novel approach to this problem based on random coding. The performance of the network coding algorithms is validated by performing extensive simulation study.Item MultiTrack: A Delay and Cost Aware P2P Overlay Architecture(2010-10-12) Podduturi, VinithThe rapid growth of peer-to-peer (P2P) networks in the past few years has brought with it increases in transit cost to Internet Service Providers (ISPs), as peers exchange large amounts of traffic across ISP boundaries. This ISP oblivious behavior has resulted in misalignment of incentives between P2P networks|that seek to maximize user quality|and ISPs|that would seek to minimize costs. Can we design a P2P overlay that accounts for both ISP costs as well as quality of service, and attains a desired tradeoff between the two? We design a system, which we call MultiTrack, that consists of an overlay of multiple kinds of Trackers whose purpose it is to align these goals. We have mTrackers that form an overlay network among themselves, and split demand from users among different ISP domains while trying to minimize their individual costs (delay plus transit cost) in their ISP domain. We design the signals in this overlay of mTrackers in such a way that potentially competitive individual optimization goals are aligned across the mTrackers. The system could also have a tTracker that acts as a gateway into the system, and ensures that users who are from different ISP domains have a fair chance of being admitted into the system, while keeping costs in check. We prove analytically that our system is stable and achieves maximum utility with minimum cost. We validated our system design using Matlab simulations, and implemented the system on ns-2 in order to conduct more realistic experiments. We showed that our system significantly outperforms two types of systems, one in which user delay is the only control dimension (forwarding traffic without considering the transit prices) and a second system in which transit prices are the only control dimension (localized traffic only). Thus, we conclude that our system, that operates in two dimensions: (1) user delay and (2) transit prices, results in minimum cost and maximum utility for fixed capacity of the system.