指定接收者可動態調整的可靠性多點傳輸協定

Abstract

多點傳輸（multicasting）對群組應用程式而言是最佳化使用網路資源的一項技術。其傳送者僅需傳送單一封包到所有群組成員，而不必針對所有的群組成員皆分別傳送一封包來達到有效利用網路資的目的。 研究指出以樹狀結構為基礎的多點傳輸協定是可靠性多點傳輸協定設計的最佳選擇。此外在Markus的研究報告中也指出，在以樹狀結構為基礎的多點傳輸協定中用來負責遺失封包重傳的指定接收者，應要能隨著網路流量及群組成員的變動而做調整。可靠性多點傳輸層協定(RMTP)是一個以樹狀結構為基礎的多點傳輸協定，但其無法動態的調整指定接收者。因此在這篇論文中，我們以可靠性多點傳輸層協定為基礎，提出了集中式及分散式兩種動態調整指定接收者的解決方案。 在我們的方法中，產生或解除一個指定接收者是以現任指定接收者的負載狀況及現任指定接收者至接收者的傳輸路徑距離為考量。在集中式的方案中，指定接收者的調整是在現任指定接收者主控下完成。而在分散式的方案中，則是由接收者間相互協調而完成。我們的研究顯示所提的方法比原始的可靠性多點傳輸協定有更佳的平均傳輸延遲時間，以及指定接收者間更好的負載平衡。

Multicasting is a technique to use the network efficiently for group communication applications. It effectively utilizes network resources by sending only one packet to all group members instead of sending multiple copies of the same data to each individual member. Research in [27] have showed that the tree-based multicast transport protocol is the best choice for reliable multicast protocol design. Besides, Markus [18] pointed out the designated points (DRs), which are responsible for retransmitting lost packets in tree-based protocol, should be adapted to the dynamic change of the network traffic and the group member. Reliable multicast transport protocol (RMTP) is a tree-based protocol, but it is unable to accommodate the dynamic change mentioned above. In this thesis, we propose both a centralized and a distributed scheme based on RMTP to dynamically adjust DRs. In our schemes, the generation and release of a new DR depends on the loading of its parent DR and the length of retransmission path from the parent DR to the receiver. In centralized scheme, a parent DR manages the process of DR adjustment. While in distributed scheme, the new DR adjustment is controlled among receivers. We show that schemes have much better performance than the raw RMTP in terms of average retransmission latency and DR load balancing.