隨著越來越多的使用者與多媒體內容快速成長下，Peer-to-peer網路技術與系統架構提供了快速且高延展性的內容散佈機制。BitTorrent及其衍生協定佔有現今網路中大部分的網路流量，並且成為目前熱門的P2P檔案分享應用。在本文中，我們進行了BitTorrent系統實際量測追蹤，並對其效能進行分析研究。我們使用檔案下載時間、最大連線頻寬、平均頻寬使用率、最大下載連線數和平均實際連線數來做為量測時的變因與指標，透過量測結果分析，我們得到了使用者端對於網路資源的使用有一些有趣的特性與結論。在效能量測部份，我們發現到在BitTorrent協定與系統中尚未被探討出的特性與觀察，然而，在先前的研究工作著重於探討系統面向和上傳端的效能量測，因此，在本篇論文的貢獻上，提供了很好的互補資訊以彌補先前研究工作的不足。此外，在本論文最後，我們透過這些有利的下載端效能特徵提供可調式配置連線方法的設計依據，藉由使用者承受的負載頻寬能力來配給合適的服務連線，經實測結果證實，可調式配置方法不僅提供穩定的成本效益，同時也改善BitTorrent客戶端應用軟體的下載效能。

With the increasing client population and the explosive volume of Internet media content, the peer-to-peer networking technologies and systems provide a rapid and scalable content distribution mechanism in the global networks. The BitTorrent protocol and its derivatives are among the most popular peer-to-peer file sharing applications, which contribute a dominant fraction of today''s Internet traffic. In this paper, we conduct the performance measurement and analysis of BitTorrent systems with an extensive volume of real trace logs. We use several downloading-side metrics, including overall downloading time, maximum of downloading bandwidth, average bandwidth utilization, maximum of downloading connections, and average number of active connections, to derive various interesting results from the downloading-side aspect of network resource usage. Performance examination learns many new observations and characteristics into the virtue of BitTorrent protocols and systems, thereby providing beneficial information for bandwidth allocation and connection control in BitTorrent Client applications. Therefore, this study is complementary to many previous research works that mainly focused on system-oriented and uploading-side performance measurements.In addition,the characteristics also provide the design rule of downloading-side network resource adaptation by using the bandwidth loading capacity to ration service connections. According our measurement result, this adaptation scheme not only provides a stable cost-effectiveness, but also improves the performance of BitTorrent client software.

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