針對家庭自動化網路中網路位址轉換的相關議題探討與解決方案

Abstract

隨著網際網路(Internet)與通訊技術的快速發展，整合家庭生活環境各種設備的家庭自動化網路(Home Automation Network, HAN)已經是近幾年來產學界重要的研究議題。家庭自動化網路必須有一套網路位址轉換(Network Address Translation, NAT)的機制來讓內部網路中擁有私有IP位址的網路設備和網際網路上的設備進行溝通。網路位址轉換，基本上是在router中利用置換IP標頭的動作，來達成網路位址轉換的功能，讓內部網路的網路設備能共用一個公眾IP位址與網際網路進行溝通。但是也正由於置換IP標頭的這個動作，讓所有與IP標頭息息相關(IP-sensitive)的應用程式在NAT router進行位址轉換後可能發生執行上的問題。為了解決NAT所存在的問題，RFC3102制定了RSIP(Realm Specific IP)這一套協定針對IP-sensitive的問題進行修正。雖然RSIP成功地解決IP-sensitive的問題，但是還存在著一些潛在的問題足以影響RSIP協定正常的運作，例如連線結束後的socket狀態為TIME_WAIT可能導致稍後的連線失敗。本研究中，我們利用輕量級目錄存取協定(Lightweight Directory Access Protocol, LDAP)的schema來解決RSIP協定所存在的問題。為了驗證解決方案的可行性，我們利用網路上OpenSource的資源整合RSIP協定與LDAP機制，開發一個Web-based的網路位址轉換系統來解決家庭自動化網路中所存在的網路位址轉換問題。在進行本系統效能評估後，發現本系統的確可以達成本論文的目標，並且只會增加少許的代價。

The home automation network (HAN) has become an important research topic for the past few years. Standards and technologies for HAN have been proposed and are frequently discussed in both academic and industry circles. The HAN has to provide the network address translation (NAT) mechanism for solving the addressing problem, since the IPv4 addressing scheme is inadequate for today’s Internet; i.e., it is impossible to assign a unique IP address to every in-home devices. All IP-sensitive applications can cause executive problems while using the NAT router. The Realm Specific IP (RSIP) provides an alternative to remedy this limitation, but complications still exist. In this paper, we propose solutions to these complications by using the lightweight directory access protocol (LDAP). We define a LDAP schema that can be used to store all necessary information generated by RSIP, and build a web-based network address translation system. The RSIP in conjunction with the LDAP schema provides a robust mechanism for dealing with the network address translation problem of HAN.