7.1 討論
PPStream 及 PPTV 等商業軟體的崛起，證明了 P2P 技術除了可被應用於檔案分享服 務外，也可被應用在隨選視訊及即時影音串流服務。本篇文章深入探討如何整合 P2P 技 術來提供即時影音串流服務，尤其是專注於提升即時影音串流系統的系統容量。我們以 樹狀 P2P 網路為背景，設計了兩個演算法，分別是 PCL 生成演算法及區域最佳化演算 法。PCL 生成演算法讓新加入網路的節點能夠被分配到適當的樹狀網路位置，使得能貢 獻較多上載頻寬的節點能夠經歷到較小的播放延遲時間。而區域最佳化演算法則提供系 統一個分散式的方式來優化系統網路，用以降低系統平均播放延遲時間。模擬實驗結果 顯示，相較於僅考慮播放延遲時間的演算法，我們所提出的演算法組合能獲得較佳的系 統容量，特別是在提供高串流資料率與限制延遲時間上限時表現尤其突出。除了模擬工 作以外，我們實作了一個基於樹狀 P2P 網路的即時影音串流系統雛型。該系統雛型讓我 們能以真實網路環境來驗證與改進所提演算法，並已實際被應用在教學用途上。
7.2 未來工作
未來我們將以雛型系統為基礎，將所提的演算法組合加以實作並設計即時串流的緩 衝與播放機制。再者，NAT 是所有 P2P 應用不可漠視的議題，除了專注提升系統容量 外，我們也需提供 NAT traversal 機制，使得系統更臻完美。
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