So it does not make sense for IBM or Sony to run dynamic routing
in their internal networks?!?
That depends. If the topology can change then you probably want dynamic
routing. Usually when I set up a Sony-sized IGP, I run dynamic in the core
and use statics to reach the edges, since while there are usually backup
paths in the core, the edges tend to be singly connected. This is identical
to the reasoning I'd use if I were designing an NSP.
That's what was meant by: