Abstract
Satellite environment provides a whole new spectrum of challenges to communications and networking. The ability to study satellite network conditions in a reproducible and controlled manner has relied mainly on simulations and experimental testbed. Investigations on network protocols and multimedia applications over satellite networks via operational hardware-based testbed are costly and inflexible while results from simulators may be inaccurate due to assumptions made during the modeling process. Hence, a satellite network emulator is proposed to overcome these obstacles as it has complementing properties of both hardware-based testbed and pure software-based simulators. The proposed emulator is to imitate the performance dynamics in IP networks over satellite links. Operating at the Medium Access Control (MAC) of Data Link Layer, the emulator is able to emulate the propagation delay and bit errors of satellite channels. This is a very useful and cost-effective approach to show the impact of satellite link delay and transmission errors on Internet services and applications. Architecturally, the paper describes how the emulator is built upon LINUX IEEE 802.3 bridging facility (brctl) and LINUX firewall (netfilter). As packet level emulation paradigm is used, the emulator is capable of producing precise satellite channel model and thus, put forward itself as a reliable, adaptable and economical alternative for research on satellite communication networking and applications. This paper presents a project on a LINUX-based satellite link emulator, including the design and algorithm of the emulator and performance evaluation of Internet applications (data, voice and video) based on the emulator. It also explains the design and setup of a flexible and expandable testbed to supplement the performance evaluation process. The effects of the satellite emulator on voice, video and data are also studied through the use of Internet applications such as Microsoft Netmeeting and TCP/IP based data transfer. Keywords: satellite emulation, IP over satellite, performance evaluation, Internet protocols. © 2003 by University of Surrey.