An animation showing how DNS works when you type the URL of a website into your web browser. This video goes into more detail than some of the others here, showing how a computer locates nameservers before finding the IP address of a domain name. Useful for older students.

This video goes into a LOT of detail about DNS and the different types of nameservers: the root nameservers, the TLD nameservers, and authoriative name servers. This is probably more detail than most students will need, but it can help understand the bigger picture, so is included here.

This 12 minute video gives a rapid overview of computer networks. Despite its short running time, a lot of topics are covered, including MAC addresses, ethernet cables, and networking hardware. Some of the concepts (e.g. collisions) may not be relevant to all Computer Science courses, but their explanations are often linked to other related concepts (for example, collisions is linked to bandwidth which in turn is linked to switches).

A really accessible overview of packet switching, using the example of accessing a web page. The steps are broken down and explained with real life examples, as a web page hosted in the US is fetched by a computer in the UK.

This video with James May takes a while to get going, but about half way through it starts to put concepts together and make it clear how the Internet works. Everything is explained clearly and in easy to understand language.