應用於NAT 中之網路服務搜尋協定

Abstract

NAT(Network Address Translator)的應用提供一個相容於現行網路架構的方式來重複使用網路位址，因此NAT的應用解決IP位址不足的問題；但是NAT隱藏內部的網路架構，這使得在外部網路的使用者無法存取在NAT內部所提供之網路服務。目前已經有一些方案來幫助使用者找尋NAT內部之網路服務，但是他們缺乏和多層NAT溝通的機制。在本篇論文之中，我們提出一個協定以協助使用者找尋在多層NAT內所提供的網路服務，我們提出的協定以動態的方式來建立或刪除網路位址轉換和IP封包過濾的規則，另外我們的協定針對多層NAT而設計的，適用於現行環境中的NAT應用。對於未來NAT的應用而言，屬於同一團體像是校園的NAT網域會連結以形成一個區域，我們提出的協定也提供一套適用於搜尋跨區域的網路服務之機制，因此我們的網路服務搜尋協定不但解決現行甚至在未來NAT應用之中找尋網路服務的問題。

The application of NAT (Network Address Translator) becomes the popular solution to IP address depletion because it provides an address reuse scheme, which is transparent to communication end hosts. However, the application of NAT hides internal network hierarchy so that services behind NAT are invisible to outside networks. Some schemes are proposed to help a client to find internal services, but they are lack of cooperation with multi-level NAT. In this thesis, we propose a protocol to assist the client in discovering services behind multi-level NAT. In our protocol, address mapping states as well as IP filtering rules are established on NAT servers dynamically that offers the feature of simple resource management. Our protocol is designed for multi-level NAT, and is suitable for current environments. For the future application of NAT, several private realms belonging to an organization such as a campus could be grouped into a domain. We also consider operations between different domains, which makes our protocol suitable for not only current NAT adoption but also the future application of NAT.