The Kerberos Authentication Process (kerberos_v2.mov)
This movie was provided on a CD with the book "OS X Server Essentials", By Schoun Regan (2006), with the filename "kerberos_v2.mov". Despite its age, it's still one of the best explanations of Kerberos I've ever seen.
Unfortunately, later updates to Quicktime broke playback of this movie. (see https://discussions.apple.com/thread/.... I tried a bunch of versions of VLC but it couldn't play the movie either.
I had to go through contortions to get this movie in a modern format: I setup a Mac OS 9 virtual machine using Sheepsaver and played the movie in it while recording the screen with Fraps.