臺灣博碩士論文加值系統

摘要
近年來拜計算機網路、多媒體應用程式的進步，人們對於網路服務的品質也愈來愈要求與重視。由於目前網路上採用相同服務等級的服務模式，可是上網的使用者或應用程式其需求確各不相同，所以導致了網路擁塞或資源分配不當而衍生出使用者對網路服務品質的不滿。因此許多專家學者為此研究並希望提出有效的解決方案。其中，差異性類別型服務被認為是可以解決此問題且最可能實現的架構之一。這架構的主要構想是希望將網路上的資料流加以分類，把服務品質要求相近的資料流整合成一個類別，而網路元件如路由器，交換器等僅需要針對這幾個類別來做資源的分配與服務。由於每個類別其服務品質的等級各不相同，故使用者可以考量自己的需求或消費能力(因為每個類別其收費標準不同)，選擇最適當的類別家來加入。
在本篇論文中，我們提供倍比式差異性類別型服務的架構。希望透過它可控制性(網路管理者可調整各類別服務品質的差異量)以及可預測性(任何時刻，高優先權的類別其服務品質必比低優先權類別的好)的優點，來改善上述的問題。對於路由器內傳送封包的機制，我們提出了動態權重式公平佇列排程演算法，並只採用小時間間隔之延遲作為量測服務品質的參數，希望透過這個方法來實現倍比式延遲差異性類別型服務的目的。除此之外，模擬的結果證明我們的演算法是可行的，而且是有效率的。

ABSTRACT
By advances in network architecture and multimedia applications, people have more and more desire on the quality of service in Internet. Because that current Internet provides same-service-to-all model and the difference between users/applications requests is much large, the congestion and unfair resource allocation make users not satisfy with the quality of service. Thus many studies focus on this problem and hope to provide sound solutions. There into, the differentiation service model is one of possible ways to implement. The main idea of this model is to aggregate these flows of similar quality requests into a class and network elements (i.e., routers, switches) only maintain per-class QoS and resource allocation. Because of the different quality levels under each class, users/applications could select the most suitable class based on his own request or class pricing.
In this thesis, we provide the architecture of the proportional differentiation service, and hope to solve the problem by its controllability (network operators can adjust the quality spacing between classes) and predictability (anytime higher classes get better service than lower classes). About the forwarding mechanism inter routers, we also provide the dynamic weighted fair queuing scheduler and take the short-term queuing delay as our measure QoS parameter. By using the method, the proportional differentiation becomes more service feasible. Furthermore, simulation results show that the proposed methods can realize proportional delay differentiation service effectively.

Contents
1 Introduction…………………………………………………………………1
1.1 Motivation………..…………………………………………………………1
1.2 Contribution…………………………………………………………………2
1.3 Thesis Outline…….…………………………………………………………2
2 Related Works……………………………………………………………….4
2.1 Integrated Service………..…………….……………………………………4
2.2 Differentiated Service………..…………….…..……………………………9
2.2.1 Routers in DiffServ network………..……….….…..……………………10
2.2.2 DiffServ Code Point (DSCP)………..……….……..……………………12
2.2.3 Per-Hop Behavior (PHB)………..……….……..………………………..12
2.2.3.1 Expedited Forwarding PHB………..……….……..….………………. 13
2.2.3.2 Assured Forwarding PHB………..……….……….….………………. 15
2.2.4 Absolute & Relative Service differentiation………..……….……..…… 16
2.2.4.1 Absolute Service differentiation………………….………..…….…. 16
2.2.4.2 Relativ Service differentiation………………..….……….……………17
2.3 Scheduling best-effort connections ……….…..……..……………………18
2.3.1 Max-min fair share…………….. ……….…..……..……………………18
2.3.2 Generalized processor sharing (GPS) ..….…..…………..………………19
2.3.3 Weighted Fair Queuing (WFQ) ……..….………………………………20
3. Per-hop Proportional Delay Differentiated Service Model ………………22
3.1 Introduction……………………………………………….. ………………22
3.2 The Proportional Differentiation Service Model…………. ………………23
3.3 Forwarding Mechanism: Dynamic WFQ Scheduling lgorithm …………25
4. Simulation Results……………………………..……………………………30
5. Conclusions and Future Work……………………………..……..…………37
Reference………………………………………………………………………38

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