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http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/732
標題: | 點對點檔案傳輸之賽局分析 A Game-Theoretic Analysis of P2P File-Sharing Systems |
作者: | Wei-Lun Tsai 蔡瑋倫 |
指導教授: | 陳健輝(Gen-Huey Chen) |
關鍵字: | 賽局理論,納許均衡,點對點,檔案分享,獎勵機制, Game Theory,Nash Equilibrium,Peer-to-Peer,File-Sharing,Incentive Mechanism, |
出版年 : | 2019 |
學位: | 碩士 |
摘要: | 點對點式網路架構常用於使用者之間的檔案傳輸與分享,藉以改善傳統主從式架構伺服器負擔過重以及易受攻擊等問題。然而,實驗結果發現點對點網路架構容易造成搭便車問題,於是我們必須借助賽局理論以設計良好的獎勵機制督促使用者貢獻自己的資源,以維持系統運作 [16]。
我們的研究從 Chiranjeeb Buragohain 等人在 2003 年所提出的模型 [2] 延伸而來。原論文根據每位使用者的貢獻來決定他/她是否能從社群獲得資源的機率函數,貢獻與機率成正相關,而效益函數則是所獲得資源去扣除自己開放頻寬給其他使用者下載的成本,在兩個人的環境下恰有兩個不崩潰的均質納許均衡,促使社群高貢獻的均衡點是穩定的。在我們的論文額外考慮了使用者對其他人所擁有資源的需求有所節制以及多重使用者的情況。在此情形下,我們發現當需求幾乎沒有節制的時候不影響原本的納許均衡;當需求有些節制的時候會壓低原本促使社群高貢獻的均衡點的貢獻量,同時該均衡點轉為不穩定,可能收斂到其他均衡點;當使用者的需求極低 (資源同質性高) 的時候整個系統反而會崩潰 (使用者均不貢獻)。此外,我們也觀察了不同條件之下納許均衡的效率隨著模型參數 (單位資源所產生之效益、需求的節制、社群人數) 的變化。 A peer-to-peer (P2P) network is commonly used for file-sharing among different users. This kind of structure can solve some common problems of centralized networks. However, experiments show that free-riding is a major problem for the P2P networks, so we have to design a good incentive mechanism with the help of game theory in order to encourage users to contribute to the community and maintain the network [16]. We use the model proposed by Buragohain et al. [2] in 2003. In the original paper, the author determines the probability function, from the contribution of each user, which controls the probability that a user can retrieve resources from the community. The probability increases with the contribution. The utility function is determined by the retrieved resources with the contribution cost subtracted. In a two-player file-sharing game, there are two non-collapsing Nash equilibria, one of which with a greater contribution is stable. In our thesis, we further consider a multi-player file-sharing game where the need for resources of each user is limited. In this game, we’ve discovered that when the limitation is not obvious, the original Nash equilibria are not affected. When the limitation is a little influential, the contribution of the Nash equilibrium with a greater contribution will be lowered and it will become unstable. When the limitation is drastic, the system will collapse. Besides, we’ve also observed how the efficiency of Nash equilibria changes with system parameters under different conditions. The parameters include the benefit drawn by one unit of resources, the limitation of need for resources, and the number of users in the network which will be defined later. |
URI: | http://tdr.lib.ntu.edu.tw/handle/123456789/732 |
DOI: | 10.6342/NTU201901991 |
全文授權: | 同意授權(全球公開) |
顯示於系所單位: | 資訊工程學系 |
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