Abstract:

Computer network design and operation are very complex despite the apparent simplicity of its components due to the distributed nature of its operation, the high number of configuration parameters, the different possible failure modes to which they should cope, etc. Theoretical exposure to this technology is clearly not enough for a future engineer, but experimentation with real equipment requires lots of resources, and therefore it is expensive in terms of equipment cost and teacher's commitment. Therefore, a need for innovative teaching approaches allowing the student to interact in a gradual path from basic networking scenarios to handling complex multi-node and multi-configuration scenarios, in a efficient and affordable way, is required.
In this paper, we describe the teaching framework deployed in the Telematics Engineering Department of the University Carlos III of Madrid (UC3M), based on: a) the use of a real laboratory – built using commercial of-the-shelf (COTS) devices – in which student teams interact with simple scenarios with commercial devices; and b) the use of a virtual laboratory, that provides the flexibility to allow students to focus on more complex problems.

Our real laboratory, with capacity for 50 students, can be equipped with up to 170 Linksys WRT54GS v4 devices, small, cheap (52€ per unit) and very popular home and office broadband routers. These routers contain a 200 MHz processor, an IEEE 802.11b/g WLAN interface and an IEEE 802.3 Ethernet interface connected to a Virtual LAN (VLAN) capable 5-port switch. Besides, these devices exhibit an interesting and very useful feature: their firmware is based on Linux (OpenWRT WhiteRussian RC6 distribution) and can be easily modified and customized to include the features needed for teaching purposes. Among the multiple modifications and extensions that we performed, we highlight the following: first, the router is configured to have 6 different (5 wired, 1 wireless) network interfaces. Second, several routing protocol daemons (based on the Quagga suite) are installed, providing a Cisco IOS-like configuration interface.

Cost is not the only limiting factor to deploy a teaching laboratory, but also room and equipment availability. Even with the large number of routers available, each pair of students can control in a exclusive way around 6 routers. We can overcome those limitations developing a virtual laboratory where different network topologies can be created and simulated in a single computer. The UC3M Virtual Lab (UViL), is a modification of VNUML to provide virtual versions of a typical laboratory host and of a Linksys router. By using these virtual versions of the real hardware, in addition to the VNUML network virtualization capabilities, UViL provides an efficient and easy-to-use tool for both instructors and students, where real network setups can be configured and tested (the only limiting factor is the processing power and available memory of the computer hosting UViL). When UViL is run, it offers a shell-like interface for each host and router of the virtualized scenario.

The extended paper will provide more details about both the real and virtual laboratories, as well as analyze how they are used in our university, comparing their associated benefits and drawbacks. We will describe our teaching experience using the virtual and COTS-based real laboratories over the last 2 years and introduce some future work.

Keywords:

innovation, technology, computer networks, cots routers, virtual laboratory.