在移動式IPv6 (Mobile IPv6)的網路架構下，移動節點(Mobile Node)不論移動到哪個網路只需要動態更換IP住址即可維持通訊連線，但是移動節點在傳遞 (Handoff) 時，仍然會產生封包遺失(Packet Loss)及傳輸效能(Throughput)下降的問題，本論文主要是針對在不同的網路負載狀況以及Mobile Node的不同移動率(Mobility)下，當Mobile Node在進行多重傳遞(Multiple Handoffs)時，將Handoff期間的封包加以緩衝再建立隧道(Tunnel)轉送，以減少封包的遺失。本論文提出了一個具有緩衝的雙重隧道建立機制(DTWB)，當移動節點接受到的無線訊號變弱時，移動節點要求網域存取路由器(Access Router) 啟動封包緩衝機制，以避免移動節點在Handoff期間封包的遺失，當移動節點在鏈結層連結到新的路由器後，舊的Access Router先建立一條到新的Access Router的隧道來轉送Handoff期間所緩衝的封包給移動節點，當移動節點取得新的網路位址後，再建立一條由新的Access Router到Mobile Node隧道。為了驗證我們所提出的DTWB機制，我們使用NS-2模擬器來模擬並且比較與其他Handoff機制的優缺點，證明我們的機制在不同的網路負載以及Mobile Node的移動率時，可以改善Multiple Handoffs造成的封包遺失率以及傳輸效能下降的問題。

Mobile IPv6 supports host mobility by dynamically changing IP addresses while mobile nodes roaming in the Internet. However, there still exist performance problems during handoffs, such as handoff latency, packet loss. When a mobile node increases its mobility, performance degradation induced by frequent handoffs grows drastically. In this thesis, we propose a dual-tunnel with buffering (DTWB) mechanism to reduce packet loss ratio during multiple handoffs. Packet buffering at access routers is initiated by mobile nodes when the received signal strength goes below a predefined threshold. The buffered packets are forwarded through dual tunnels, of which the first tunnel is established between the old access router and the new access router, and the second tunnel is established between the new access router and the mobile nodes. For the purpose of evaluation, we perform experiments on NS-2 simulation. The simulation results demonstrate that our proposed mechanism can minimize the packet loss ratio and increase the throughput during multiple handoffs.

第一章 導論 1
1.1 研究動機 1
1.2 研究方向與方法 1
1.3 章節介紹 3
第二章 移動式IPv6之背景與相關研究 4
2.1 Mobile IPv6 4
2.1.1 名詞定義與解釋 5
2.1.2 Mobile IPv6運作方式 6
2.1.2.1 基本運作 6
2.1.2.2 路由最佳化程序(Route Optimization) 7
2.2 階層式Mobile IPv6網路架構 8
2.2.1 HMIPv6的相關研究 9
2.3 Mobile IPv6 的Handoff問題 10
2.4 Mobile IPv6 Handoff的相關研究 10
2.4.1 針對Movement Detection Delay的相關研究 11
2.4.2 針對Handoff期間Packet Loss的相關研究 11
2.4.2.1 減少Handoff延遲之機制 11
2.4.2.2 封包緩衝機制 14
2.4.3 其他改進Handoff效能的相關研究 15
2.5 Handoff相關機制比較 16
2.6 本論文的多重傳遞機制 17
第三章 具有緩衝的雙重隧道機制 18
3.1 多重傳遞時的封包緩衝與轉送 18
3.2 具有緩衝的雙重隧道機制 20
3.3 機制運作流程及演算法 22
3.3.1 MN運作流程 22
3.3.2 MN演算法 23
3.3.3 MN所修改的封包格式 24
3.3.4 AR運作流程 25
3.3.5 AR演算法 27
第四章 模擬架構與結果分析 29
4.1 NS模組架構 29
4.2 模擬環境與網路拓樸 31
4.3 模擬結果與分析討論 32
4.3.1 針對不同網路負載的模擬環境 33
4.3.2 針對不同MN移動率的模擬環境 36
4.3.3 針對不同緩衝區大小的模擬環境 38
第五章 結論與未來工作方向 40
5.1 結論 40
5.2 未來工作方向 40
REFERENCES 42
INDEX 46

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