Very clear diagrams and explanations of PAN, LAN, WLAN, and WAN. The diagrams are clear and include the location of key hardware such as switches, clients, and servers.The following pages also have good coverage of the other Computer Science networking topics, including network topologies.
Computer Network Types is a short but clear explanation of the main types of networks in Computer Science. It covers PAN, LAN, MAN, and WAN with very clear diagrams and explanations.
The BBC's Connecting to the Internet does a good job of explaining the requirements for connecting to the Internet as well as the major media types (including, copper cable, fibre optic, ADSL, and 3/4G). The pages are very detailed and give advantages and disadvantages for each connection type.
About Tech has one of the better explanations of network cable types, covering the essentials including coaxial, twisted pair, and fibre optic. The hyperlink-studded text makes it easy to students to find out about any related terms or concepts which confuse them.
This excellent page from Akamai features interactive charts to help students visualise Internet trends. Students can view a global map of Internet speeds (which holds a few surprises) and customize the graphs to show data and changes from which countries and time periods they want. A great way of examining potential digital divides.
The most common Internet protocols - TCP/IP, FTP, POP3, STMP, VOIP, and HTTP are given the BBC treatment in this page. Although largely text based, the resource clearly explains each term and uses examples to highlight how these protocols are used in everyday life, even if we don't notice them.
In this simple game students must attempt to corrupt, kill, or delay data packets as they are sent across the screen. This game might now seem very educational at first, but on later levels (5 onwards) the data transmitted has additional features to detect corruption. For example, packets are sent with a sequence number (just like an IP packet), so delaying a packet no longer causes problems. This game can lead to some good classroom discussions about how network protocols prevent the problems shown in the game.
The Internet gives an overview of how the Internet works and also clearly explains the difference between circuit switching and packet switching.
This is an interactive version of the classic parity magic trick, which can also be performed with playing cards in from of a class (it generates a bit more enthusiasm when done live!). The activity is simple: set the parity bits correctly (the system uses even parity), then as the computer to randomly flip a bit. It should be possible to detect the change by examining the parity.
The card flip 'magic' game is a great idea from Computer Science Unplugged. The teacher sets up a grid of black/white cards and asks students to turn over one card without the teacher seeing. Using parity rules, the teacher is able to 'magically' determine which card the students turned over. This is a really fun game which demonstrates how simple techniques like odd/even partity can be used to solve significant problems.
The Computer Science Unplugged page has a range of support material: instructions for teachers, videos of the activity being performed, and a PDF download with extension activities and details about check digits in ISBNs.
BBC Bitesize has clear revision materials for the three main network topologies: star network, bus network, and ring network. As always, their diagrams are very clear and easy to understand, and each topology has a clear table of its advantages and disadvantages.