Mobile IP 中多點傳播協定之研究

Abstract

隨著無線網路技術的成熟與可攜式設備的普及，加上人們對移動式辦 公室的需求，促成了行動計算的興起。這種新型態的電腦運作方式使得使 用者可以在任何時間地點存取資料或執行運算。由於行動計算需要特殊的 網路環境，使得行動式網路在此時應孕而生。 目前行動式網路的標準 Mobile IP，對於傳播模式並無具體的規範。傳播模式一般可分為單點傳 播、廣播以及多點傳播。前兩者的優缺點眾所皆知，而多點傳播由於能節 省整體網路頻寬的消耗以及發送端的資源消耗，恰好能因應行動式網路環 境中，無線傳輸頻寬的限制以及可攜式設備在能源消耗上的限制。因此以 多點傳播做為行動式網路的主要傳播模式，似乎是相當可行的。目前已知 的多點傳播協定，均是以有線網路為假設環境而發展出來，並無考慮行動 式網路環境的特殊需求與可能面臨的問題。 本篇論文的目的在於提出 一個改良的協定架構，在行動式網路環境提供多點傳播服務。首先介紹行 動式網路的定義、特性與目前的標準Mobile IP。接著介紹多點傳播的定 義以及縱覽目前的協定標準，同時對已知的多點傳播協定架構在行動式網 路遭遇的問題進行分析，並探討現有的參考文獻所提出的解決方案。接下 來，我們將根據現有的解決方案做進一步的改良，提出一個能在Mobile IP網路環境下運作的多點傳播協定架構。同時建構出模擬系統，對於所提 出的協定架構與現有的協定架構進行比較分析，以驗證改良方案是否達成 預期的改善目標。 The rapidly expanding technology of wireless communications and portable computer and the need of moving office make it possible for mobile computing to arise. As a new a kind of operating style, mobile computing allows user to access information anywhere at any time or perform computation. To satisfy the special requirement of mobile computing, mobile internetwork become available to provide mobile computer attaching to the Internet. The current specification of mobile Internetwork ,Mobile IP, has no solidregulation about communication modes.The modes can be classified into unicast , broadcast, and multicast. The first two modes have well-known effect and weakness. Multicast provides benefits including global savings on network bandwidth and resource savings at the sender. These benefits make it possible to use multicast as the main communication mode of mobile internetwork. Currently, many multicast protocols are developed on the assumption that the Internet with wireline communications is the only communication environment and designed without considering the special requirement of mobile internetwork. This thesis is organized as follows. Firstly we introduce the definition and specification of mobile internetwork and multicast. Then we examine the problem of multicast on the mobile internetwork and review solutions from the literature. Moreover, we propose an alternative approach to provide multicast service on the Mobile IP environment. Finally a simulation model is developed to study the effectiveness and efficiency of the proposed approach.