國立臺灣大學電機工程學系暨研究所廖婉君2006-07-252018-07-062006-07-252018-07-062002-07-31http://ntur.lib.ntu.edu.tw//handle/246246/7897本計畫是總計劃「多媒體與多重服 務之數位用戶迴路通訊系統」下之子計畫 四「數位用戶迴路上網路電話與代理伺服 器服務之設計」之第二年計畫。 本計畫以網路協定設計分析及服務軟 體設計為主，以設計數位用戶迴路通訊系 統網路上之網路電話服務及網路伺服器的 通訊協定為主要課題，第一年中我們分析 WWW 在非對稱網路上的效能並加以改良；第 二年我們則著重於增進網路上多媒體會議 的傳輸效能。 在寬頻網路中，傳統上一個網路會議 乃是以多點控制單元(MCU)來集中控管會 議，當會議成員有封包要送出時，先送到 MCU，再由MCU 分送到各成員，這種星狀的 拓樸將使得網路頻寬浪費，尤其在非對稱 網路上將使得原本就較小的上行頻寬更顯 不足，而且使得MCU 容易成為瓶頸；因此 我們提出一個應用層會議樹的方法，可大 量節省頻寬使用，降低加入會議所需等待 的時間，並將它與Megaco/H.248 結合，使 得我們的方法可直接與數位迴路接取多工 器(DSLAM)結合。模擬結果亦顯示所建立的 樹其大小約為最小生成樹的1~1.2 倍，十 分有效率。 本計劃成果已發表於IEEE ICME 2001 (International Conference on Multimedia and Expo 2001).As a sub-project of the joint project entitled “xDSL Multimedia Multi-service Communications System,” this project, named “Voice over IP (VoIP) and Web Proxy over xDSL,” attempts to design both VoIP and Web proxy services over xDSL developed by the other sub-projects in a five-year span. In the first year, we have investigated and improved the effect of xDSL systems on WWW traffics. In the second year, we have focused on improving the performance of network conferences. Traditionally, a multipoint conference takes place through an MCU (Multipoint Control Unit), which centralizes the control of the conference. This approach requires each conference member have a direct connection to the MCU, thus forming a star topology for the conference. Our proposed approach establishes a shared, cost effective conference tree for the conference taking advantage of existing VoIP protocols. We have also developed a simplified analytical model and conducted simulations to compare the performance of the proposed approach. The results show that our approach enjoys the advantage of lower join latency, better bandwidth efficiency, and more cost effective as compared to other approaches. The preliminary results of this project have been published on the proc. IEEE ICME 2001.application/pdf286485 bytesapplication/pdfzh-TW國立臺灣大學電機工程學系暨研究所數位用戶迴路網路電話代理伺服器層會議樹 Megaco/H.248ADSLInternet TelephonyVoIP Application Layer Conference TreeMegaco/H.248reporthttp://ntur.lib.ntu.edu.tw/bitstream/246246/7897/1/902218E002041.pdf