Cross-domain correlation is a technique I (think?) I created when studying for the CISSP exam. It's the process of picking a random topic in one domain, and then trying to relate it to another random topic in the other 7 domains. The point was to confirm my knowledge of the concepts across a broad spectrum of CISSP topics. The idea is that everything in security is in some way related to another.
This particular cross-domain correlation video is about how IPSec relates to all other random topics. Become a member of the website for more videos like this as well as other CISSP videos: