Global routing
Beginner
The planning pass of routing: choosing a rough path for every connection across a coarse grid, the way you plan a road trip city by city before opening street maps.
Novice
The first, planning pass of routing. It gives every net a rough path through a coarse grid of tiles (GCells), usually with a layer for each piece, while staying within how many wires each tile border can hold and keeping total wire length and via count low. It hands this plan (route guides) and a map of crowded areas to detailed routing.
Expert
A typical modern global router splits multi-pin nets into two-pin pieces with Steiner trees, tries cheap L- and Z-shaped routes, maze-routes what still overflows, rips up and reroutes under rising congestion costs, then assigns layers. Overflow left at the end can turn into detours or rule violations later.
Explained in Routing (Design Flow).
See also: GCell (global routing cell), Detailed routing, Negotiated congestion.