頻寬移動高效率DQDB都會網路

Abstract

分散式雙佇列巴士（DQDB）已經被美國IEEE-802.6採用為大都會區域網路的標準，它在獲取巴士的使用權是基於每一個工作節點內部所維持的佇列，DQDB不論在網路的大小與速度為何時，皆可以達到接近於整條巴士容量的工作量以及具有很小的存取延遲時間。然而，當網路的大小與工作量增加，DQDB在使用權的分配上，造成了各個工作節點上不公平的問題。為了消除此不公平的問題，各種不同的技術提出了他們對此問題的解決方法。在此篇論文中，首先對DQDB作一個介紹，並分析其不公平的問題，除此之外，對那些提出來欲解決此問題的技術作一個概略性的總覽，以及分析這些技術較好及較弱的地方。然後介紹一種新奇的技術，稱為頻寬轉移技術（BSM），BSM依據工作負載須求的基準，分配頻寬給網路上各個工作節點。除此之外，BSM允許每個工作節點依其工作負載量做區域性或全盤性的須求以得到相對的一個或多個資料保留時槽段。因此，BSM不論是在網路的大小，速度與負載為何情況，皆可提供高效率與維持其存取延遲上的公平性。最後，此篇論語文以模擬的方法展現出BSM在工作量存取的公平性確實是優於其他技術。

Distributed Queue Dual Bus (DQDB) has been adopted as an IEEE 802.6 standard for Metropolitan Area Networks (MANs). The access mechanism is based on an implicit distributed queue maintained at each node. DQDB was shown to achieve maximal aggregate throughput (near the bus capacity) and minimal access delay independent of the size and speed of the network. However, as the size and load of the network increases, significant throughput unfairness problems of the DQDB access mechanism have been revealed. To eliminate the unfairness problems, various mechanisms have been proposed. This thesis first overviews DQDB and analyzes its unfairness problems. In addition, a survey of these mechanisms, including an analysis of their strengths and weaknesses is given. The thesis then proposes a novel mechanism, called Bandwidth Shift Mechanism (BSM). BSM dynamically allocates bandwidth to different sections of networks on demand basis. In addition, BSM allow nodes to issue locally and globally significant requests for making single or multiple-slot reservations, respectively. Consequently, BSM offers high and fair throughput independent of the size, speed, and load of networks. Finally, the thesis also demonstrates throughput fairness and superiority of BSM over other mechanisms via simulation results.