Red routings are lanes leaving the vertex, routing below the staircase to W
Blue routings are lanes that are entering the vertex, routing above the staircase from V
Routings at Vertex level
Routings above vertex V at W plane level
Routings below vertex W at V plane level
Routings at the underplane level of V
Any port of a vertex will either be routing to a higher vertex or
it will have a route coming into it from a lower vertex - only one route can
be used at any time. The layout shows all possible out and all possible in for each
port.