The End-to-End Argument
Functions belong at the endpoints; lower layers can only optimize, never guarantee. The single most useful design principle in networking.
Principle
Saltzer and Schroeder's Principles
Least privilege, fail-safe defaults, economy of mechanism; plus the confused deputy as the canonical violation.
Kerckhoffs's Principle and Perfect Secrecy
Security lives in the key; and Shannon's proof that the one-time pad is unbreakable and impractical for the same reason.
Minimum Description Length and Occam's Razor
Simplicity, formalized as compression; the bridge from information theory to model selection in PAC learning and VC dimension.
Hyrum's Law and Postel's Principle
Every observable behavior of your API is depended upon by someone; and the robustness principle that made that worse, plus the modern case against it.