具地域性動態家代理伺服器之應用層行動管理機制

隨著無線網路的蓬勃發展，行動管理機制的提供變得日益重要。兩個重要而有代表性的機制MIP及ROMIP已先後被提出來支援行動管理，然而仍受限於三角路由、控制命令過多及機制支援性等問題而效率不彰。標準MIP機制下因為三角路由關係使得傳輸延遲、封包遺失問題出現；雖然ROMIP利用位址更新通知CN紀錄使用者目前位址來避免三角路由問題，然而要求網際網路上所有電腦都需支援行動管理是非常困難的，而且控制命令的負擔也變得比較重。先前研究成果提出的行動管理機制改良稱為HH-MIP。HH-MIP嘗試搭配ROMIP以降低控制命令的傳輸量但仍保有ROMIP傳輸效率的好處，而也證明協定能有效降低傳輸路徑及換手延遲。雖然HH-MIP成效極佳，但是此為建立在所有Foreign Network均需有支援THA (FA)路由設備的前提之下。然而現有網路上，並不是所有路由器均能支援行動管理協定，因此該機制的佈建上較缺乏彈性。本論文提出改良的行動管理機制稱為DHA-LA，目標為打破部署上的限制，不希望更動到現有路由設備，因此嘗試將THA提升為Application layer行動管理機制伺服器。DHA-LA提出局部佈署的優勢並且解決其衍生造成的尋找合適THA之問題，而模擬結果，證實本機制在局部佈建的形式下，能趨近於甚至優於其他完全佈建的協定。

關鍵字

行動管理機制； MIP ； ROMIP ； HH-MIP ； THA ； FA

並列摘要

Mobility management is important to wireless networks, but increased speed and efficiency are hampered by problems of triangular routing, signaling overhead and binding cache support. Two important and representative approaches, Mobile IP (MIP) and Route Optimization in Mobile IP (ROMIP), were proposed to provide mobility management. In the standard MIP mechanism, triangular routing increases transmission delay, packet loss, and additional signaling. ROMIP uses a binding update to inform a corresponding node of the current IP address of the mobile node. This approach can avoid the triangular routing problem and provide a smoother handoff. However, it is very difficult to implement a binding cache in every node of the entire Internet. Moreover, it also results in large signaling overhead. In previous work, we focus on proposing an enhancement of mobility management, called Mobile IP with Home Agent Handover (HH-MIP), to enjoy most of the advantages of ROMIP but with only a small increase of signaling overhead. The HH-MIP approach is an efficient mechanism to eliminate ROMIP shortcomings without introduces large signaling cost, and the results show that HH-MIP could reduce both transmission path and handoff latency efficiently as compared with the previous mechanisms. Although HH-MIP has great performance, it demands all routers in Foreign Networks to support combined functionalities of both Temporary Home Agent (THA) and foreign Agent (FA). Nevertheless, not all of routing devices can adjust to implement the functionality of HH-MIP in the existing Internet. Thus, we found that the protocol is inflexible on deployment of THA/FA. In this thesis, we propose an adaptive mobility management scheme called Dynamic Home Agnet with Location Awareness (DHA-LA). We attempt to implement the mobility management protocol on application layer. Therefore, the DHA-LA could break the deploy limition of HH-MIP and doesn’t need to modify any routing devices in the Internet. DHA-LA proposes the advantage of partial deployment and resolves the problem of global THA discovery. Simulation results demonstrate that the performance of DHA-LA which is partial THA deployment can close to or better than other protocols that are fully FA established.