I am a pre-service teacher located in Townsville, I would introduce networks to my students through the use of concrete manipulatives. I believe introducing students to concepts such as networks (especially early on) could be potentially problematic based on their ability to make high level connections. I would introduce something like a ball dipped in glue, and then have a small group of students hand it around to one another. I would have another group hand a ball around to one another than had no glue. I would use this strategy to identify the idea of a LAN to them, and that the students in the no-glue group were insulated from the threat of sticky hands (a potential virus) because they are a closed network. I would then have one of the students with the glue ball throw it to the other group, and explain to them that it is roughly the equivalent of a virus being introduced to a network of computers.