Nick Feamster is a professor at Princeton University, who teaches a course in computer networking. He's kindly created 210 videos which cover all of the major topics covered in the course, and published them on Youtube for free. They're each just 2 or 3 minutes in length, so it's easy to pick and choose the particular topics you're interested in. And being from a Princeton professor, they're an easy watch and also very informative.
Head to https://www.youtube.com/playlist?list=PLpherdrLyny-zJw95jcE-uJkcsIAG1MEn in your browser if you want to check them out. And my thanks go to Lex Davidson for telling me about this great resource.