In the last chapter, we have seen that in scaled technologies it is imperative to reduce the distance that signals traverse at the low, highly resistive metal layers. It is also necessary to reduce the capacitive load on channel wires, as well as the active area consumed by the routing multiplexers so that the lengths of different wires can be reduced. At the same time, not all connections will be used by the router to implement timing-critical signals of user circuits, meaning that while general improvement in the above three metrics is highly desirable, further benefits can be reaped if optimization specifically targets the connections commonly used by the critical signals. Needless to say, while designing the switch-block to meet these criteria, care must be taken that overall routability is not excessively damaged.