This network simulation tool from GCSEComputing.org.uk is a great tool for teaching networks (topic 3.3 Networks) to ITGS students. Students can add a variety of hardware devices to the virtual network including different types of servers (file, print, etc), hubs, switches, and routers, and shared peripheral devices such as printers.
The tool can be used in three modes: Step by step, which guides students through the process of creating and optimizing a client-server network; simulation mode, which shows bandwidth use as components such as hubs and switches are added and configured; and Build a network mode, which lets students freely create a network by adding clients, servers, hubs, and other networking equipment.
Whichever process they use, the tool can help students learn about essential networking components and terminology in the ITGS syllabus, including the differences between hubs, switches, and routers, peer-to-peer versus client-server network configurations, different server functionality, and network monitoring and administration.
The activity also makes a good introduction to wider networking questions related to the benefits of networking in application areas such as business or education. Personally I used it with my grade 12 students as a networking refresher before studying network monitoring and Internet filtering in the Politics and Government section of strand 2.