寬頻整體服務數位網路在遠端多工端點的壅塞控制策略

Abstract

在最近這幾年中，寬頻整體服務數位網路漸漸被使用在通訊網路的架構上 。它能提供多媒體上的應用，以及非同步傳輸模式。在本論文中，展現了 數種資訊的傳輸模型，如數據、語音和動態影像，尤其是動態影像，我們 考慮了換景的情況。然後，我們將這些傳輸模型用來分析非同步傳輸模式 網路的擁塞控制。我們使用雙臨界壅塞控制及捨棄較不重要封包的策略。 在數學模式中，系統分析、佇列分佈、封包遺失率和封包平均等待時間皆 有完整的推導。從其結果中，這些控制的程序能使其效能比沒有控制的效 果有顯著的增加。在第一章中，我們提出一個部份捨棄的雙臨界壅塞控制 的策略。在佇列長度超過高臨界值時，雙臨界擁塞控制將被啟動，並持續 到佇列長度落於低臨界值以下為止。當一群新來的封包超過空餘佇列所能 容納的量，則系統接受這些封包直到佇列滿為止，剩餘的則捨棄。其主要 的目的在於提高網路的使用率。在第二章中，其方法和第一章類似，只是 將〝部份捨棄〞改變為〝全部捨棄〞。當一群新來的封包，無法全部容納 於空餘佇列中，則這整群封包將全部被捨棄。其主要的目的在於保持資訊 的完整性。 In the late few years, Broadband ISDN (B-ISDN) has been raised attention as a communication architecture which can support multimedia applications on asynchronous transfer mode (ATM) networks. This paper presents several source models such as data, voice, and video. Especially on video model, we considered scene change condition. Then, we applied those model to ATM network for congestion control. We use two level threshold on buffer queue length to selective discard some less significant packets. A mathematical model of this system is analysed and queue length distributions are derived. It is shown that the control procedures can achieve significant performance improve- ment over uncontrolled system. In chapter 2, we propose a two-threshold reactive congestion control strategy with partial reject. The two-threshold conges- tion control strategy will be active when the queue length exceeds a higher threshold and will continue until the queue length drops to a lower threshold for each type of traffic. When the batch size of a new coming arrival exceeding the remaining free buffers of its queue, the system will accept packets until there is no free buffer, and these exceeding packets are re- jected and lost. The major purpose is to get high throughput. In chapter 3, the strategy used in here is similar to chapter 2, but replace ``partial reject" to ``complete reject". When the batch size of a new coming arrival exceeding the remaining free buffer of its queue, the whole batch packets will be complete reject. The purpose is to keep message integrality.