在NCTUns模擬器平台上提供IPv6的Simulation和Emulation的功能

Abstract

隨著全球資訊網際網路的使用者急遽增加，原本的IPv4 的位址空間 ( addressing space) 已漸漸不足以應付網際網路使用者的需求。於是，下一個世代的網際網路協定 IPv6 已被訂定出來以提供更大的位址空間及增加網際網路協定的使用彈性和能力。IPv6已逐漸獲得重視並有相當多相關此一通訊協定的研究。然而，若在真實環境下進行網路研究要花費大量的時間和金錢，且結果不易重複呈現。在模擬的環境下，所有的網路狀況及設定都是可以簡單地重覆呈現且花費低廉，因此使用者不僅可以容易地得到重覆的實驗結果，還可以節省大量的時間和金錢。

基於上述關於在模擬平台上進行研究的優點，我們開始研究如何在網路模擬器的平台下開發IPv6的模擬。NCTUns是一個創新的模擬器，它整合了OS kernel、simulation engine和應用程式。所以在本篇的論文中，可分成三大部份：第一部份是在NCTUns環境下提供IPv6的模擬。在此部份中，我們利用修改Linux kernel和網路模擬器的engine 及module code逹成在NCTUns上提供純IPv6的模擬。第二部份是在NCTUns環境下同時提供IPv4和IPv6的模擬，在這一部份中，我們增加二個module來逹成IPv4和IPv6的混合模擬。最後一部份則是在NCTUns環境下提供IPv6的Emulation，在此部份,我們修改Linux kernel和增加一個IPv6 emulation daemon。修改Linux kernel是為了使Linux具備類似Divert Socket的功能。增加IPv6 emulation daemon是為了使simulation machine能正確的和external host建立connection及傳輸封包。

Due to the rapid growth of Internet, IPv4 (Internet Protocol Version 4) may not provide enough address space in the future. Thus, IPv6, the next generation of Internet protocol, has been proposed to deal with this issue. IPv6 has opened many novel aspects of researching areas and become a hot topic. Therefore, developing an IPv6-based evaluation environment is valuable and important. In the network-research domain, simulation is a useful approach for users to evaluate the performance of IPv6 with acceptable cost. This thesis describes how to make NCTUns support IPv6 simulations and emulations, including the mixed networks of IPv4 and IPv6.

Since NCTUns is a novel network simulator that integrates the OS kernel, the simulation engine, and user-level applications into a whole simulation environment, the work of this thesis involves the modifications of Linux kernel, the simulation engine, and the development of new protocol modules in NCTUns. First of all, to support the pure IPv6 simulation in NCTUns, the Linux kernel, the simulation engine and modules are modified to provide the pure IPv6 simulation. Second, to support the simulation of mixed networks of IPv4 and IPv6 in NCTUns, two modules are developed to accomplish the conversion between IPv4 packets and IPv6 packets. Finally, to support the IPv6 emulation in NCTUns, we modified the Linux kernel to let it be capable of redirecting some specified packets to the user-level applications (This mechanism is called “divert socket” in FreeBSD) and wrote new user-level programs to allow packets with different IP versions to be transmitted correctly between a real host and a simulated host.