I have chosen to undertake VLSI CAD as a part of my electronics degree and I came across this statement (Source : Naveed Sherwani, Algorithms for VLSI Physical Design Automation, 3rd edition , Chapter 8. Global Routing , Page 251) :
I had an issue in understanding as to why channels and 2d switchboxes are routed first. I cannot comprehend what it is trying to convey.