Finally, for improving the security of P2P-based CDNs against peer misbehaviors, we present a stochastic analytical model for understanding the performance of the P2P rating systems, which are widely engaged for safeguarding P2P-based CDNs. We study two representative designs, namely the unstructured self-managing rating (UMR) system and the structured supervising rating (SSR) system with the model under various network environments and adversary attacks. We also propose a configurable loosely supervising rating (LSR) system, and show that the system works inexpensively, and could make tradeoffs between the features of the UMR and the SSR system, thus providing a better overall performance according to the application context. / Peer-to-Peer (P2P) networks, especially P2P-based content distribution networks (CDN), have enabled large-scale content distribution without major infrastructure support in recent years. However, P2P-based CDNs suffer from performance issues such as stability and scalability, as well as security threats due to their decentralized nature. In this thesis, we address the performance and security issues in P2P-based CDNs. / We first consider a BitTorrent-like file swarming system. A simple mathematical model is presented for understanding its performance. With the model we find that under the stable state the peer distribution follows an asymmetric U-shaped curve, which is determined and influenced by various factors. We also analyze the content availability in the system and study its dying process, in which the integrity of the content is endangered. An innovative "tit-for-tat" unchoking strategy enabling more peers to finish their download jobs and prolong the system's lifetime is proposed. We then consider an application-layer tree-like overlay for the synchronous live media multicasting system. In particular we address the instability issue of the multicast overlay caused by nodes' abrupt departures. A set of algorithms are proposed to improve the overlay's stability based on actively estimating the nodes' lifetime model. To support our solution, we have studied the lifetime model via real-world measurements, and have formally proved the effectiveness of the algorithms. The experimental performance evaluation indicates that our algorithms work inexpensively, and could improve the overlay's stability considerably. We also consider the asynchronous on-demand media (MoD) streaming using P2P networks. In particular, we aim to improve the scalability of the system by proposing a novel probabilistic caching mechanism. Theoretical analysis is presented to show that by engaging the proposed mechanism with a flexible system parameter, better scalability could be achieved by a MoD system with less workload imposed on the server. Moreover, we show by simulation that our proposed caching mechanism could improve the streaming service conceived by peers under various conditions of server capacities and network environments. / Tian, Ye. / "July 2007." / Adviser: Kam-Wing Ng. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1119. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 180-193). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_344042 |
| Date | January 2007 |
| Contributors | Tian, Ye, Chinese University of Hong Kong Graduate School. Division of Computer Science and Engineering. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, theses |
| Format | electronic resource, microform, microfiche, 1 online resource (xv, 193 p : ill.) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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