由於網路快速的蓬勃發展，因為壅塞所造成封包高遺失率及網路資源低使用效率，目前已有一些壅塞控制機制被提出。網路壅塞的原因是由於訊流之間相互競爭頻寬所造成，而分類服務架構(Differentiated Services Architecture)便是在允許不同等級的訊流可以獲得不同頻寬資源之服務品質(Quality of Service)觀念下被提出。此外，隨機預丟封包偵測(Random Early Detection, RED)是一個可以預先偵測及避免發生壅塞之有效方法，它是根據封包在佇列(Queue)中的長度達到某一定程度時便隨機將一些封包預先丟棄，此舉可避免網路在達到真正壅塞時而發生癱瘓。然而，隨機預丟偵測法對於網路在不同的壅塞情形之控制能力尚不夠強韌(Robust)。在本研究論文中首先提出一個新的可適性預丟機制演算法，稱之為OURED，以加強對於網路在發生不同壅塞程度時可以應付的強韌度。OURED可適性訊流控制機制亦可被使用於分類服務架構中的邊緣路由器(Edge Router)。OURED是由兩組封包預丟機制所組成；一是Over RED，另一是Under RED。Over RED是當網路的實際速率大於目標速率時用來加速封包的丟棄機率，Under RED則反之。經由大量的實驗結果顯示，OURED比目前已被提出的方法，如MRED、Self-Configuring RED、FRED等，可得到更好的效果。
本研究論文所提的另一個訊流控制架構為Age-Based封包丟棄機制。由於目前網路上傳輸的檔案大小差異越來越大，我們提出一個以訊流存活長度(age)為判斷基礎的演算法來增進檔案傳輸之效能。當網路發生壅塞現象時，對於正在傳輸封包的訊流將會被切成三個不同的等級(EF, LPAF,HPAF)。實驗的結果顯示，此Age-Based封包丟棄架構可以在大部分網路發生壅塞情況時，獲得有效率的傳輸品質。

Many congestion control mechanisms have been proposed to solve the problems of a high loss rate and inefficient utilization of network resources in the present Internet. This problem is caused by competition between traffic flows while the network is congested. Differentiated Services (DiffServ) architecture permits the allocation of various levels of traffic resource requirements needed for Quality of Service (QoS). Random Early Detection (RED) is an efficient mechanism to pre-drop packets before actual congestion occurs, and it is capable of introducing a random early packet dropping scheme, and based on the queue length in reaching a certain degree of fairness for resource utilization. However, it still suffers from a lack of robustness among light traffic load, or in heavy traffic load using fixed RED parameters. In this dissertation, we modified the RED scheme and proposed a novel adaptive RED model, which we named the OURED model, to enhance the robustness of resource utilization so that it could be utilized in the DiffServ edge router. The OURED model introduces two additional packet dropping traces, one is Over Random Early Detection (ORED), which is used to speed up the dropping of packets when the actual rate is higher than the target rate, and the other one is the Under Random Early Detection (URED), used to slow down the packet dropping rate in the reverse situation. The simulation results show that OURED is not only more robust than MRED in resource utilization, but that it also can be implement efficiently in the DiffServ edge router.
Another model proposed in this dissertation is the Age-Based packet discarding Traffic Conditioner. For the reason that the file sizes of on going flows are fairly disparate on the current network, we propose an “Age-Based” packet discard scheme in the Traffic Conditioner of a gateway, to improve the performance of file transmission. The on going flows will be grouped to three classes of priority according to their “age” as network congestion occurs and the simulation results show that the proposed model can work efficiently in most of the congestion conditions.

中文摘要……………………………………………………………………………i
Abstract iii
List of Figures v
List of Tables viii
Chapter 1 Introduction 1
1.1 Research Motivation 1
1.2 Recent Related Research 3
1.3 Organization of the Dissertation 5
Chapter 2 Overview of the QoS Protocols 6
2.1 Integrated Services Network 8
2.2 Resource Reservation Protocol 10
2.3 Multi Protocol Label Switching 12
2.4 Internet Protocol version 6 (IPv6) 12
Chapter 3 Overview of the Differentiated Services Network 15
3.1 Architecture of DiffServ Network 16
3.1.1 Differentiated Services Domain 18
3.1.2 DiffServ Boundary Nodes and Interior Nodes 19
3.1.3 DiffServ Ingress Node and Egress Node 19
3.1.4 Differentiated Services Region 20
3.1.5 Bandwidth Broker 20
3.2 Traffic Conditioner 23
3.3 Assured Forwarding Service 26
3.4 Expedited Forwarding Service 26
3.5 DiffServ Implementation 27
Chapter 4 Review of Adaptive Queue Management Mechanisms 30
4.1 Random Early Detection 30
4.2 RED Analysis 31
4.3 A Self-Configuring RED Gateway 32
4.4 RIO and MRED 33
4.5 FRED 36
4.6 Weighted Fair Queue 37
4.7 A Feedback Control Extension to DiffServ 39
4.8 CAC-RDS Relative DiffServ Model 40
Chapter 5 A Novel Adaptive Traffic Conditioner –OURED Model 42
5.1 ORED Dropping Trace 43
5.2 URED Dropping Trace 45
5.3 Performance Evaluation of OURED 47
5.4 The general form of c1 and c2 values in the OURED 50
5.5 The Advantage of the OURED Model 53
Chapter 6 OURED in DiffServ Network 55
6.1 The Implementation of OURED in DiffServ Network 55
6.2 Performance Evaluations of OURED in DiffServ 57
6.2.1 OURED in two priority classes 57
6.2.2 OURED in different C1, C2 conditions 61
6.2.3 OURED in different RTTs 62
6.2.4 Comparison OURED with RIO 64
Chapter 7 The Age-Based Packet Discarding Traffic Conditioner 68
7.1 Proposed Age-Based TC 70
7.2 Marker in the Age-Based TC 73
7.3 Dropper in the Age-Based TC 75
Chapter 8 Performance Evaluation of the Age-Based TC 77
Chapter 9 Conclusion and Future Research 84
Appendix 86
References 87
授權書 92

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