一個提供快速網路位置轉換之代理行動IP 架構

Abstract

近年來隨著各種無線網路技術的發達以及行動裝置的普及，人們可在這些裝置上透過無線網路存取各種服務，例如線上影音串流。另一種需求也油然而生－不但要能在固定的位置無線上網，還要在上網的同時移動而不受影響。代理行動IP (Proxy Mobile IP, PMIP)可讓行動裝置於不同的子網路中漫遊而不造成上層的連線中斷，且不需對行動裝置多作修改。不過其標準僅支援點對點的網路類型，而目前最普遍的 IEEE 802.11網路則屬於廣播型網路。另一方面，在目前IPv4可用位址不足的情況下，另外提供IP位置給行動裝置是一大難題。NAT (Network Address Translation) 是目前最常使用的解決方案，卻不與MIP (Mobile IP)或PMIP相容。本論文提出一種名為NAToD (Network Address Translation on Demand) 的新式跨階層的NAT架構，可解決原本MIP/PMIP與NAT不相容的問題，並可在 IEEE 802.11網路下運作。本架構僅需更新網路存取點(Access Point)的軟體即可讓行動裝置擁有IP的可移動性，不需修改行動裝置，可降低建置的成本及時間。本架構亦可在IP轉送時略過部分流程而節省時間。從實驗的結果顯示，在大部分情況下NAToD可得到較佳的效能。

A variety of wireless technologies have been popularized in recent years and enable users to connect to the Internet from almost everywhere. This brings the demand on the user mobility that allows a mobile device roams from one place to another without any application disruption. Proxy mobile IP (PMIP) provides network based mobility management to support unmodified mobile device but it cannot apply on non point-to-point networks suck as IEEE 802.11. On the other hand, the demand for IP addresses by mobile terminals can be solved by NAT which is unfortunately not compatible with MIP/PMIP. In this thesis, we propose a novel cross-layer network address translation scheme called Network Address Translation on Demand (NAToD) and integrate it with proxy mobile IPv4. The scheme allows PMIP running on the most popular IEEE 802.11 networks, and it only requires software upgrading on the AP itself. Doing this way, we can reduce the deployment cost as well as shorten the system deployment time. The experiment result shows that NAToD achieve better performance in most cases.