為了提供使用者移動性的能力，IETF制定了行動式IP與行動式IPv6，讓使用者在不同IP網域下移動時，仍然可以保持與網路的連線而不需中斷。而階層化行動式IPv6乃是改進移動式IPv6在進行交握程序時，所引起的延遲時間過長的問題所提出的改進方案。藉由設置移動錨點(Mobility Anchor Point)負責處理移動節點在區域中的移動，來減少移動節點對本地代理人(Home Agent)及對應節點(Correspondent Node)進行交握程序的機會，除了降低網路頻寬的使用，也能讓移動節點更快速的與網路連線，而不至於中斷太久的時間。。 本篇論文所提出的移動錨點選擇機制，除了讓移動節點改以停留時間與及移動到其他移動錨點的計算方式來計算其移動性外，並加入動態抽象錨點的概念，使移動錨點能擴大服務範圍，使移動節點不必經常更換移動錨點，來減低移動節點對本地代理人及對應節點重新進行繫結更新的機會。也讓各個移動錨點間可以互相支援，使移動錨點不至有過載的情形發生。但相對的也必須付出區域性繫結更新時，多餘的延遲時間，但相較與本地代理人及對應節點間的延遲時間來看，可以算是較有效率的方式。 在考慮動態抽象移動錨點方面，則必須找出適當的拆除成本，與及如何更有效率的抽象移動錨點拓樸。 In order to support mobility for users，Mobile IPv4 and Mobile IPv6 were proposed by IETF as the main protocols. Because of some disadvantages of Mobile IPv6, HMIPv6 has been proposed to reduce the signaling overhead and handover latency by deploying Mobility Anchor Point (MAP) in the IPv6 network. In this thesis, we proposed a MAP selection algorithm, It can let Mobile Node select an appropriate MAP by its dwell time and handover probability. And we also introduce the concept of dynamice abstract MAP, it can effectively reduce the frequency of Inter-domain handoff and can avoid the overload in MAPs. Finally, We use NS2 to simulate the performance of the proposed scheme is. The simulation results show that scheme can reduce the handover latency and the load of each MAP more efficiently.We also need to condiser what cost is appropriate to destroy the abstract MAP,and how to construct a abstract MAP topology efficiently.
