Most fundamental network design attribute should be simplicity.
Network Design should be simple! Simplicity is the first network design best practice that I want you to remember. If you have been in the field long enough, you have probably heard about the KISS principle.
If you are a regular follower of my blog, you have maybe heard about the SUCK principle as well.
KISS stands for Keep It Simple Stupid. But do you really know what the simple part is ? Can every part of the network be a simple ?
Unfortunately NOT ! It just cannot be ! But still you should on simplifying as much of your network as possible.
As I have indicated in the past here, intelligence should be at the edge of the networks and network core should be as simple as possible. If you read the above article, you will see some examples. ( There are different opinions about the place of simplicity in networks. Some researchers believe that if the core has some intelligence the overall network complexity is reduced ).
Networks have many protocols, technologies. Understanding each of them might be easy but interaction between them creates complexity.
In my CCDE training sessions, I like to give the Pepper and Salt example to explain this point.