The Hourglass Model

Today I learned about The Hourglass Model.

The argument is that adding more functionality to the abstraction layer might reduce the number of applications this layer supports.
Example: functionality of NATed subnetworks limit IP layer to support P2P applications. This fragment also mentions the connection between the breaking of symmetry and weakness of NAT.
I've been using orthogonality principle unconsciously and had no proper name for till I read this paper. This paper also mentions "End-to-End argument," which I wasn't aware of.
The End-to-End argument in System Design. This paper discusses a design principle of a function placement that has been used for many years.

Jul 2, 2019. Berlin