網路環境的變動會影響資料傳輸品質，為確保對用戶的服務品質，以MPLS技術為主的MPLS VPN便在此趨勢下逐漸成為當紅的應用。本論文主要是針對在BGP/MPLS VPN上應用不同等級的差別式服務做各種效能的評估，並比較在增加VPN功能後與Non VPN之間的差異。
我們用OPNET模擬器產生所要研究的網路，藉由改變上面的環境參數值與設定不同的網路狀況（例如網路擁塞或斷線），將模擬所得之資料作統計與分析。首先，我們發現在MPLS VPN上，除了資料封包必須增加標籤外，PE路由器也要能記憶各種協定、搜尋IP路由表及轉送路由之各種表格。如此，不僅使整個MPLS VPN資料傳輸的overhead變大，而且CPU的負擔也加重了。
另外，就建立整個路由信息的收斂時間而言，MPLS VPN會比Non VPN來得多。然而，當網路發生斷線時，MPLS VP N重新尋找路徑的收斂時間卻比Non VPN所花費的要少，因此Throughput也較佳。倘若網路發生擁塞，由於MPLS VPN 本身對於所要保證的資料流（EF Traffic）建立不同替代路徑，使得這類資料流的Delay比在Non VPN上的小；其中又因斷線造成所要保證資料流( EF Traffic )改走其他LSP路徑，而同斷線LSP之Traffic Flow在MPLS VP N 與 Non VPN 所建立替代路徑不同，造成通過之 Throughput 也以MPLS VPN較佳。從模擬得知其下降之幅度又以Background BE Traffic之Throughput下降最大，而EF Traffic之Throughput下降最小。

Nowadays, MPLS VPN has become a widely used solution on the issue of QoS guarantees against unexpected changes of network environments. This thesis investigates the system performance of the BGP-based MPLS VPN, which supports per class differentiated services. The results are compared with those without VPN.
In this study, the target network is simulated through the OPNET simulator. Through adjusting the network parameters and creating different scenarios, such as network congestion and disconnection, we make statistical analyses based on the simulation results. It is observed that in addition to increasing the labels contained in each packet, MPLS VPN require PE routers be capable of supporting more protocols, such as searching for IP tables, and transferring various tables for the use of routing. Therefore, introducing VPN may increase processing load and overhead for data transmission.
On the other hand, MPLS VPN may take longer convergence time in establishing entire routing messages than Non-VPN. However, when network disconnection occurs, the former has better throughput than the latter due to the shorter convergence time in the search of new routes. Also, if the networks become congested, the transmission delay of EF traffic in MPLS VPN is smaller since the alternative LSP for it is pre-established. For the same disconnected LSP route, MPLS VPN network also achieves better throughput, because the guaranteed EF traffic can be rerouted via different LSP routes. According to our simulation results, the background traffic has the largest throughput decrease, while the EF Traffic has the least.

第一章 導論
1-1 研究動機
1-2 研究的方向
1-3 論文架構

第二章 MPLS VPN之相關研究背景
2-1 MPLS VPN的發展背景
2-2 MPLS VPN網路的基本架構
2-3 MPLS VPN與差別式服務的整合
2-4 MPLS VPN應用上之優點
2-5 MPLS VPN如何交換信息
2-6 MPLS VPN資料流如何傳遞
2-7 PE 路由器的離開路徑過濾(ORF)
2-8流量工程的有效實施
2-9 MPLS VPN的潛在問題

第三章 具有差別式服務MPLS VPN架構探討
3-1 模擬網路需求之設計
3-2 整體設計架構之描述
3-3 網點間收斂時間的討論
3-4 關於端點對端點路由斷線之收斂

第四章 模擬與結果分析
4-1 MPLS VPN與MPLS之間overhead的比較
4-2 用戶網點間收斂時間的比較
4-3 當網路發生擁塞時的比較
4-4 當網路發生故障時收斂時間的比較
4-5 故障時Throughput的比較

第五章 結論與未來分析
5-1 結論
5-2 未來的分析

參考文獻
索引

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