基於DHT應用層群播之可信賴同儕式多串流機制

Abstract

近年來，同儕網路上的影音串流應用已愈來愈普及。然而，此類網路高度不穩定的節點狀況仍舊存在，此乃是導至傳輸率下降與接收端影音串流品質不穩定的重要因素。本論文中，我們提出一個在同儕網路上以多串流來傳送封包的機制，稱為ConStream，以改善這個問題。在這個機制中，整個待傳的內容將被看成由多個multi-stripe所組成，並且每個multi-stripe將被配給多棵群播樹來同時傳送串流封包。在這些串流中，我們會加入校驗封包（parity packets），以使得接收端能夠回復傳送過程所遺失的封包。除此之外，在我們所提出的ConStream方法，每個串流的傳輸速度(delivery rate)相對於其它方法的單一串流將能有效的減半，每個節點對於串流傳送的負擔也將因此降低。模擬結果顯示，我們的方法相較於Scribe-PRM與SplitStream，在不同程度的節點斷線率（MTTFs, mean time to failures）下，皆具有較高的傳輸率（delivery ratio）。

Streaming applications in P2P networks are more and more popular recently. However, high degree of churning in peer populations is a common problem, and it would result in a low delivery ratio and instable quality of received multimedia. In this thesis, we propose a P2P multi-streaming scheme, called ConStream, to improve this problem. In our scheme, the whole content is composed of multi-stripes, and each of the multi-stripes will be distributed to multiple multicast trees and be forwarded concurrently. Also, we insert parity packets into streams so that clients can recover lost data. Furthermore, the delivery rate of each stream in our ConStream is only half of the original single streaming. That is, the burden of each node is lower than those nodes using single streaming to forward. Simulation results show that the proposed ConStream has a higher delivery ratio than Scribe-PRM and SplitStream under various MTTFs (mean time to failures).