Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/51576
標題: 一個在光封包交換器上具遲延時間認知能力之封包排程方法
Latency-Aware Packet Scheduling for Output-Buffered Optical Switch
作者: 林偉 
關鍵字: 資訊工程--硬體工程;Optical packet switching;光封包交換;packet scheduling;fiber delay line;PIFO queue management;packet latency;封包排程;光纖延遲線;插入先出行列管理;封包遲延時間;基礎研究
摘要: 
This proposal addresses the problem of optimizing packet scheduling for an output-buffered optical switch to minimize end-to-end delay and packet loss. We consider accumulated packet latency as the primary factor for determining system performance of optical switches using fiber delay lines (FDLs). Effective control over accumulated packet latency can not only reduce end-to-end delay, but also lower packet loss rate. For this reason, we devise a priority function for ranking packets in an output buffer with FDLs. The priority function gives preference to packets with high accumulated latency and low residual distance. Packets of this sort are accelerated for the destinations, and the closer, the faster. The proposed research work is divided into three main tasks. First, we propose to design a latency-aware scheduling algorithm that manages a Push-In-First-Out (PIFO) queue for storing delayed packets, and schedules packets for departure based on the priority of latency. Secondly, we plan to develop a new Markovian model to approximate the performance of the latency-aware packet scheduling algorithm with the PIFO queue. We will adopt an iterative computation scheme to compute packet state distribution for convergence, and derive equations for calculating probabilities of end-to-end delay and packet loss. Finally, we will construct a packet-level simulator. The simulator is intended to verify the correctness of the analytical model to be developed. Through simulation, we are also interested in performance comparison of the latency-aware scheduling algorithm with other scheduling disciplines.

此計畫探討光輸出端緩衝交換器之封包最佳化問題,用以減少封包之點到點延遲及丟棄損失。我們認為累積延遲其實是決定光交換器系統效能之主要因素。有效控制累積延遲可減少點到點延遲及降低封包損失率。基於這理由,我們設計了一個優先權計算式,用以排列暫存於光纖延遲線中之封包。對於高累積遲延或低剩餘距離的封包,此優先權計算式會給予較高的權重。此類之封包會被加速送抵終點,而且是越接近時越快。我們所提出之研究計畫包括三項主要工作。第一項工作是設計一個排程演算法。此演算法用來管理暫存封包的一個插入先出行列,及依照遲延優先權安排封包離去次序。第二個工作是發展一個新的馬可夫模式。我們打算用這馬可夫模式去估計排程演算法所達成的效能。我們將利用一個重覆計算法使封包狀態分布率之計算得以收歛。而且我們將會導出用以計算點到點遲延及封包損失概率之公式。第三個工作是製作一個封包層的模擬器。此模擬器用來驗証我們所推導出來分析模式的正確性。同時,我們也打算透過模擬的方式去比較我們所提排程演算法與其他方法之效能。
URI: http://hdl.handle.net/11455/51576
其他識別: NSC98-2221-E005-054
Appears in Collections:資訊科學與工程學系所

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