Hui Ying Kin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 62-64). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.10 / Chapter 1.1 --- Motivation --- p.10 / Chapter 1.2 --- P2P small-world solution --- p.11 / Chapter 1.3 --- Balance of this thesis --- p.12 / Chapter 2 --- Background --- p.13 / Chapter 2.1 --- Small World phenomenon --- p.13 / Chapter 2.2 --- Internet Flash Crowds --- p.16 / Chapter 2.3 --- Dynamics in the small world network --- p.17 / Chapter 3 --- Small-world Overlay Protocol --- p.19 / Chapter 3.1 --- Overview --- p.23 / Chapter 3.2 --- Join Cluster Protocol (JCP): --- p.25 / Chapter 3.3 --- Leave Cluster Protocol (LCP): --- p.29 / Chapter 3.4 --- Object Lookup Protocol (OLP): --- p.31 / Chapter 3.5 --- Experimental Results Of Comparing with Other Structured P2P Networks --- p.33 / Chapter 3.5.1 --- Performance of object lookup: --- p.33 / Chapter 3.5.2 --- Effect of object lookup performance under different net- work sizes and number of long links: --- p.34 / Chapter 3.5.3 --- Comparison of Clustering Coefficient: --- p.35 / Chapter 4 --- Protocols for Handling Flash Crowd --- p.39 / Chapter 4.1 --- Static Flash Crowd --- p.40 / Chapter 4.2 --- Dynamic Flash Crowd --- p.44 / Chapter 4.3 --- Experimental Results for Replicating Popular Object --- p.45 / Chapter 4.3.1 --- Comparison between Chord and SWOP --- p.46 / Chapter 4.3.2 --- Comparison on Queue Size --- p.48 / Chapter 4.3.3 --- Variation on object request rate --- p.49 / Chapter 4.3.4 --- Variation on Number of Long Link Neighbors (k) --- p.50 / Chapter 4.4 --- Experiment Results for Examining the Effects on Traffic Loadings --- p.51 / Chapter 5 --- Performance Analysis --- p.53 / Chapter 5.1 --- Lookup complexity of SWOP --- p.53 / Chapter 5.2 --- Average time used for replicating item to all clusters in SWOP --- p.56 / Chapter 6 --- Related Work --- p.59 / Chapter 7 --- Conclusion --- p.61

Ma Tianbai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 49-51). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Incentive P2P System Overview --- p.6 / Chapter 3 --- Resource Distribution Mechanism --- p.11 / Chapter 4 --- Resource Competition Game --- p.22 / Chapter 4.1 --- Theoretical Competition Game --- p.22 / Chapter 4.2 --- Practical Competition Game Protocol --- p.26 / Chapter 5 --- Generalized Mechanism and Game --- p.33 / Chapter 5.1 --- Generalized Mechanism with Incentive --- p.33 / Chapter 5.2 --- Generalized Mechanism with Utility --- p.35 / Chapter 6 --- Experiments --- p.38 / Chapter 7 --- Conclusion --- p.48

Lin Wing Kai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 90-96). / Abstracts in English and Chinese. / Abstract/ 摘要 --- p.i / Acknowledgement --- p.iv / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- """We are not alone""" --- p.1 / Chapter 1.2 --- Definition of P2P systems --- p.3 / Chapter 1.2.1 --- Terminologies --- p.4 / Chapter 1.2.2 --- Principles --- p.5 / Chapter 1.3 --- From sharing to replication --- p.7 / Chapter 1.3.1 --- Replication: why and how --- p.7 / Chapter 1.3.2 --- Advantages of P2P replication systems --- p.8 / Chapter 1.3.3 --- Typical replication approaches --- p.10 / Chapter 1.3.4 --- Difficulties in replication: resource allocation and replication strategy --- p.10 / Chapter 1.3.5 --- Why do peers cooperate? --- p.12 / Chapter 1.4 --- Contribution of this thesis --- p.13 / Chapter 1.4.1 --- Thesis organization --- p.13 / Chapter 2 --- Background Study --- p.15 / Chapter 2.1 --- Introduction --- p.15 / Chapter 2.2 --- Overview of P2P systems --- p.16 / Chapter 2.2.1 --- The original story --- p.16 / Chapter 2.2.2 --- Switching to decentralization --- p.16 / Chapter 2.2.3 --- Peer availability --- p.17 / Chapter 2.2.4 --- Other than file sharing --- p.18 / Chapter 2.3 --- Understanding replication --- p.20 / Chapter 2.3.1 --- File availability redefined --- p.20 / Chapter 2.3.2 --- Storage requirement analysis --- p.21 / Chapter 2.3.3 --- MTTF analysis --- p.22 / Chapter 2.3.4 --- Replica placement --- p.24 / Chapter 2.3.5 --- Other performance enhancement schemes --- p.27 / Chapter 2.4 --- Understanding cooperation --- p.28 / Chapter 2.5 --- Discussions --- p.30 / Chapter 3 --- Performance of erasure code replication --- p.32 / Chapter 3.1 --- Introduction --- p.32 / Chapter 3.2 --- Parameters definition --- p.33 / Chapter 3.2.1 --- File availability: whole file replication --- p.33 / Chapter 3.2.2 --- File availability: erasure code replication --- p.34 / Chapter 3.2.3 --- Properties of erasure code replication --- p.35 / Chapter 3.2.4 --- Effects of replication parameters --- p.36 / Chapter 3.2.5 --- Optimal value of b --- p.39 / Chapter 3.2.6 --- Analytical derivation --- p.40 / Chapter 3.3 --- Some practical considerations --- p.42 / Chapter 3.3.1 --- Cost of erasure code replication --- p.42 / Chapter 3.3.2 --- Sensitivity analysis --- p.44 / Chapter 3.4 --- Concluding remarks --- p.45 / Chapter 4 --- Distributed replication strategies --- p.48 / Chapter 4.1 --- Introduction --- p.48 / Chapter 4.2 --- The P2P replication system --- p.50 / Chapter 4.2.1 --- Erasure code replication --- p.50 / Chapter 4.2.2 --- Peers modelling --- p.51 / Chapter 4.2.3 --- Resource allocation problem --- p.52 / Chapter 4.2.4 --- Replication goal --- p.54 / Chapter 4.3 --- Decentralized adaptation --- p.56 / Chapter 4.3.1 --- Neighbour discovery and parameters exchange --- p.56 / Chapter 4.3.2 --- Storage resource estimation --- p.57 / Chapter 4.4 --- Heuristic strategies --- p.58 / Chapter 4.4.1 --- Random strategy --- p.58 / Chapter 4.4.2 --- Group partition strategy --- p.59 / Chapter 4.4.3 --- Highest available first (HAF) strategy --- p.61 / Chapter 4.5 --- Case studies --- p.65 / Chapter 4.5.1 --- Simulation results --- p.66 / Chapter 4.6 --- Concluding remarks --- p.69 / Chapter 5 --- Before cooperation: why do peers join? --- p.72 / Chapter 5.1 --- Introduction --- p.72 / Chapter 5.2 --- Information sharing club (ISC) model --- p.73 / Chapter 5.3 --- An example: music information sharing club --- p.75 / Chapter 5.4 --- Necessary condition for ISC to grow --- p.76 / Chapter 5.4.1 --- Music information sharing club example with simple requests --- p.78 / Chapter 5.5 --- Concluding remarks --- p.81 / Chapter 6 --- Conclusion --- p.83 / Chapter A --- Proof in this thesis --- p.86 / Bibliography --- p.90

Thesis (M.S.)--Baylor University, 2005. / Includes bibliographical references (p. 78-81).

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

published_or_final_version / Computer Science / Master / Master of Philosophy

The persistence of cooperation is a longstanding problem in the social and biological sciences. Recent advances of peer-to-peer (P2P) networks manifest as a promising platform to experiment and contribute to theories and algorithms on cooperation. In this thesis, by and large, we view P2P systems as an economy in which incentives are critical to stimulate contribution. Indeed, a P2P system can be considered as a society where different behaviors can emerge, and an empirical platform to understand cooperation and mimic evolving population. Specifically, we consider the problem of cooperation from two perspectives. First and foremost, autonomous nodes are strategic and selfish, who are reluctant to cooperate solely for public good. We investigate incentive scheme design for cooperation in P2P live media streaming networks. The general approach of protocol decomposition shows that practical incentives can only be guaranteed by efficient peer selection, due to stringent playback deadlines. Striker strategy is then proposed so as to align the optimal peer selection of heterogeneous nodes with social welfare maximization, the efficiency of which is validated by repeated game modeling and extensive simulations. The hidden philosophy is to coerce non-cooperative peers into cooperation by collectively implementing punishment threats. This is analogous to strikes and coercion implemented by organizations like unions in human society. On the other hand, just as node selfishness, competition and struggle for survival raise another problem for cooperation. Similar to human society and biological systems, we envision that diverse strategies—some are more exploitative, while others more altruistic—could be deployed by selfish participants to compete against interacting nodes and gain performance advantages. In such a variegated environment, our coevolutionary perspective aims to understand cooperation and rationalize the coexistence and success of diverse behaviors. Population games and evolutionary game theory provide analytical tractability, while learning and evolutionary dynamics are proposed to evolve strategies. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

 Peer-to-Peer (P2P) file sharing is one of the most commonly used methods for sharing files over a network, especially large files such as videos or music recordings. In North America, P2P file-sharing networks occupied approximately 50% of the network traffic in 2011 [3]. Many files shared through P2P networks are related to Internet piracy or unintentional file sharing. Foxy P2P network, a typical search-based P2P network, is in the spotlight for sensitive file sharing. Peers download the files by using keywords instead of resource links. Therefore, the investigation mechanisms developed to identify the first seeder in Bit-Torrent network – another type of P2P network [54], cannot be applied to this scenario. Identifying the first seeder is the critical step in P2P investigation. The investigator cannot collect necessary evidence without locating the first seeder. Therefore, conducting forensic analysis is impossible. Moreover, validating the actual first seeder will be challenging when more than one uploader is identified. This study started by analyzing different P2P networks and comparing their underlying features. Categorizing the P2P file-sharing networks resulted in the identification of the key functions for file sharing. Two difficulties in Foxy network investigation, namely, unknown file publication time and uncertainty of network coverage by uploaders and downloaders, were also highlighted. To further examine the Foxy P2P network, a controlled testing environment for the P2P network was developed in a network simulation environment (i.e., NS-3). Tests were conducted in the simulation environment, and the effects of various attributes (file size, file transfer rate, file popularity) on the growth of the number of uploaders (represented by the seeder curve) were analyzed. Results demonstrated that the shape of the seeder curve was affected by the file propagation feature of the file-sharing activity. The slow-rising period, which represented the competition for the file content being shared among peers, was recorded at the initial stage of file sharing in the P2P network. Competition for file content is one of the key factors related to the success or failure in performing P2P investigation through the simulation environment. An investigation algorithm and four validation rules were proposed based on the above key factor to perform P2P investigation. Through controlled and randomly selected experiments, the investigation could be applied to the search-based P2P file-sharing environment as long as the required slow-rising period in other P2P networks was followed [68]. Analysis of the experimental results demonstrated the ability of the proposed investigation model and the validation rules. The results verified and confirmed the observed seeder in the P2P file-sharing scenario if competitions among downloaders for the shared file content existed. The limitations of the P2P investigation and validation model were also discussed. / published_or_final_version / Computer Science / Doctoral / Doctor of Philosophy

Peer-to-peer (P2P) systems have achieved outstanding success during the past decades and much efforts has been put into investigating incentive mechanisms for strategic P2P networks. In the numerous studies of P2P system, efficient resource utilization has always been a critical factor in designing incentive schemes. Most existing studies try to encourage strategic peers to contribute more to the system, in order to maximize the resources. However, without considering how to effectively measure contributions and without adopting well-designed trading policies, simply motivating more contributions could lead to outcomes that do not match the original intention. This thesis, therefore, focuses on the investigation of efficient resource utilization in strategic P2P systems. First, it is found that increased contributions in terms of upload rate does not necessarily lead to better system performance. Observing that different chunks have different values to both the system and individual peers, a value-based metric is devised to measure contributions instead of using rate-based metrics. A variation of BitTorrent is also proposed, called value-based BitTorrent (VBT). VBT is found to effectively punish the strategic behaviors of an underreporting chunk map, and there is a positive correlation between investment and return for cooperative peers in VBT networks. Moreover, VBT always outperforms BitTorrent in terms of system performance. Second, taking the chunk value in the reciprocity process into consideration, the overpayment problem in a BitTorrent network is investigated, and four side effects of overpayment are identified. A new scheme is proposed to visualize overpayment and a series of metrics is proposed based on this method to quantify overpayment. The proposed value-based approach is found to be able to alleviate the degree of overpayment and consequently relieve the side effects of overpayment. Third, the performance of popular protocols in a P2P file-sharing system is investigated from the perspective of overpayment. These protocols are studied in two directions, when the measurement metrics are varied and when trading policy becomes tighter. The correlations between fairness, performance, and robustness are also examined. Finally, because overpayment is a fundamental problem of improper price setting, and auction is a widely used and effective method in setting prices in distributed systems. Auction is analytically proved that it is able to lead to optimal price without overpayment. However, most existing auction schemes are based on credit, which could induce a huge overhead in maintaining a monetary system, and monetary systems also have many inherent problems, such as inflation. The efficacy of applying an auction-like approach in P2P systems without money is investigated. A simplified version of the barter-based auction-like approach is tested in P2P file sharing and its overpayment degree is evaluated. Moreover, a novel barter-based auction-like approach is proposed for a P2P streaming system, and it is found that it can successfully punish strategic behaviors, with overall system performance outperforming a tit-for-tat strategy. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

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