在Linux上實作具有Diff-Serv功能之軟體路徑器

Abstract

在日益壅塞的網際網路中提供QoS（Quality of Service）保證是必然的趨勢，也是項重要的挑戰，多種標準已因應而生。IETF（Internet Engineering Task Force）先前制定了Integrated Service（Int-Serv）來提供較佳之傳輸QoS，但是因為它使用之RSVP（Resource reSerVation Protocol）協定有擴充性不佳的缺點，因此近年來IETF制定出新的網路技術Differentiated Server（Diff-Serv ）來改善Integrated Service之缺點，並且降低了實作時複雜度。Linux 作業系統因其開放性，吸引很多學術研究採用它做為作業平台。不斷推陳出新的Linux 核心已提供了多種訊務控制（traffic control）功能，這些訊務控制功能是在Linux 上實現Diff-Serv 不可或缺的重要元件。在本篇論文中，我們將在Linux 中的user-space上設計一個程式來控制Linux 核心中的訊務控制功能，以實作出具有Diff-Serv 功能之軟體心路徑器（edge router）與邊界路徑器（core router）。在這些軟體路徑器上，我們將可以自行設定各種類型訊務的頻寬和其他重要參數，並且同時提供AF（Assured Forwarding）、EF（Expedited Forwarding）、BE（Best-effort）類型的傳輸服務。在本篇論文中，我們也設計了６個實驗來驗證這些軟體路徑器的功能。實驗結果顯示我們所實現出之軟體核心路徑器與邊界路徑器確實能正確地處理封中之DSCP（Differentiated Services CodePoint）值，並且提供Diff-Serv的功能。A Quality of Service (QoS) guarantee has become a must and a challenge for the ever-blocking Internet. A variety of strategies have been proposed ever since. Integrated Service formulated by Internet Engineering Task Force (IETF) facilitates a better QoS, but its Resource reSerVation Protocol (RSVP) suffers a drawback of poor scalability. Therefore, a new strategy called Differentiated Server has been formulated by IETF to improve Integrated Service and reduce the complexity in implementations. Thanks to its openness, Linux operating system has been adopted by many researchers as their operating platform. The ever-updating Linux has developed many traffic control functions, which are indispensable elements in implementing Diff-Serv on Linux. In this paper we design a program on the user-space of Linux to exploit traffic control functions to implement Diff-Serv-aware software core routers and edge routers. Furthermore, we examine the functions of the software routers through six experiments. Experimental results show that both our core router and edge router can correctly deal with the. differentiated services codepoint (DSCP) within packets and offer Diff-Serv-aware service.