An introduction to medieval cities and cloud security

This is indeed an excellent description of one security model. I would, however, add a note to the reader that there has been some discussion over the last few years about whether it's actually safe to have an inner trusted zone, or whether every single house has to be completely defended to the point where a compromise of the outer wall is almost a non-event. (Google's BeyondCorp being the best known example)

Note that there is still the concept of "inner trusted zones" with something like BeyondCorp, the difference being that access to the zones is controlled by credential via an Access Proxy rather than by network topology.

Of note, individual servers do NOT need to be individually fully defended, they are protected by a firewall which only allows the Access Proxy.

quick search shows this Peter Norvig blog

http://norvig.com/carcassonne.html

fun

I love these types of articles, great work!