Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/8373
標題: ATM網路中對自相似交通流量之控制
On Self-similar Traffic Regulation in ATM Networks: Using Multiple Leaky Buckets Algorithm
作者: 孫正倫
Sun, Cheng Lun
關鍵字: ATM;非同步傳輸模式;self-similar;multiple leaky buckets;congestion control;自相似性;多重漏桶;壅塞控制
出版社: 電機工程學系
摘要: 
ATM網路中的壅塞控制為網路管理的核心。壅塞控制的主要功能在提升網路的效能,同時也使網路資源得以公平地分配給每一位使用者。為了能設計出適當的流量控制器,我們必須先瞭解交通流量的特性。目前相關於交通流量特性的研究證實,在ATM網路中的可變位元速率之視訊,具有自相似性。若忽略此種特性,則會在網路效能分析時,產生過度樂觀的預估值,進而導致網路資源配置不足。換言之,自相似性對ATM網路的分析、設計及控制具有實質的影響。
本篇論文將針對ATM網路中具有自相似性的視訊,發展出回授式流量控制器。此控制器的核心部份是由多重漏桶演算法所構成。我們假設,自相似交通流量經由累加之後具有統計多工增益。為了能利用這種特性,我們將同一個虛擬路徑中的所有漏桶予以整合,亦即共享各漏桶的漏失率及緩衝區,以期網路資源得以被更有效地利用。
我們所設計的多重漏桶演算法,乃是根據各個漏桶的緩衝區佔用率,動態調整各漏桶的漏失率和緩衝區大小。為了驗證系統的效能,我們使用十個MPEG1及十個經由合成所產生的自相似交通流量,作為系統的輸入。實驗結果顯示,多重漏桶演算法所造成的細胞遺失率為傳統之漏桶演算法的1/3  1/10000。為確保合法使用者的服務品質,我們還設計了與回授式流量控制器整合的保護措施。當多重漏桶演算法加上這項保護措施之後,可完全防止違規使用者對其他合法使用者之服務品質的影響。
關鍵字: 非同步傳輸模式、自相似性、多重漏桶、壅塞控制

Congestion control lies on the heart of the general problem of traffic management for ATM networks. The primary function of congestion control is to maximizing network performance in throughput and delay while maintaining a fair allocation of network resources to the users. Feedback flow control is one of the solutions which has been extensively studied. Before designing an appropriate traffic rate regulator, understanding the characteristics of traffic sources is the most essential work. Recent traffic measurement studies have demonstrated that the variable bit rate (VBR) video over ATM networks exhibits self-similarity. If the self-similarity is ignored, it will result in overly optimistic performance predictions and inadequate network resources allocation. In other words, the self-similarity has practical impact on analysis, design and control of ATM networks.
In this thesis we proposed a feedback rate regulator for self-similar VBR traffic in ATM networks, based on multiple leaky buckets (MLB) mechanism. A basic assumption was made that the multiplexing gain does exist for aggregated self-similar VBR traffic. Therefore, unlike the conventional leaky bucket (LB), the leaky rate and buffer capacity of all LBs are shared in the same virtual path, in order to use network resources more effectively. In our mechanisms, the leaky rate and buffer capacity of each LB are dynamically adjusted base on the buffer occupancy. To validate the performance of our mechanisms, ten real world MPEG1 traffic traces and synthesized self-similar data series are used in our experiment. The simulation results show that the cell loss rate has three to more than ten thousand times improvement comparing to the conventional leaky bucket method. Moreover, when the protection policy integrated with feedback rate regulator is added to the MLB, it can totally prevent the malicious sources from degrading the quality of services of all established connections.
Key words: ATM, self-similar, multiple leaky buckets, congestion control.
URI: http://hdl.handle.net/11455/8373
Appears in Collections:電機工程學系所

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