網路的發展，促進了許多資訊交流。近年來，由於網路速度的大幅提升，不僅是網頁，許多音樂、影片等多媒體檔案都可以在網路上互相流通。而隨選視訊系統(Video-On-Demand)則被認為影音串流發展的主流。但是由於影音串流需要的頻寬較大，所以更容易在主從式架構中發生供應源超載，來不及處理；供應源線路頻寬不足，造成封包流壅塞的現象，使得服務效能降低。所以近年來點對點架構(peer-to-peer scheme)可以分散供應源減輕主伺服器負擔，其相關研究與試驗也越來越多。點對點架構的優點是隨著使用者人數的增加，還是可以展現其良好的擴充性。 因此本論文提出了一個點對點串流的架構P2PHB，結合了Harmonic Broadcasting架構，將原本的分頻道設計適用在點對點網路中，並且以應用層群播的方式進行串流的轉送，對於點對點網路架構中節點可能失效的情形提出了偵測與復原的機制。如此一來負責影音串流的伺服器原始供應源就可以減少許多串流負擔，使得系統的擴充性更好。除此之外，還有針對錄放功能提出實行策略，讓使用者可以自行調整撥放點，提供如快轉、倒轉與暫停之錄放功能，且在進行特定錄放功能如跳轉、倒轉時，較DirectStream有更好的片段命中率。 本文除了提出上述功能之架構與演算法，並針對熱門度分析各節點提供快取之容量分析，另針對PPBS與P2PHB之異同進行模擬比較分析，可證明本方法在起始延遲具更佳表現。 Because the significant improvement of network bandwidth, many objects like movie, music or web pages can transfer over internet quickly. In this applications,Video-On-Demand is widely applied in variety of services today. Though the bandwidth requirement of streaming is higher, limited bandwidth is still the main problem. Recently ,Peer-to-Peer (P2P) technology gives us a hand for solving the congestion in server,and has much scalability. Hence we propose a new method named “peer-to-peer streaming system using harmonic broadcasting scheme(P2PHB)” to solve this problem. In this system, we combine the peer-to-peer streaming system and Harmonic Broadcasting scheme. By using application layer multicast to relay the streaming from peer to peer and we also propose a peer fault detection and recovery mechanism to handle the highly dynamic environment in peer-to-peer system to archive higher stability, Besides this ,our system can provide VCR function like Fast-Forwarding , Back-Forwarding and pause.About the cache in peer ,we proposed a popularity mechanism to dynamically adjust cache size in peer. After all we evaluate the performance of our method by simulation.The results show that P2PHB has lower start up delay then PPBS scheme and higher hit-ratio of segment than Directstream.
