If I was revisiting, I'd probably eradicate the layer and pick a fixed number of flow types with distinct headers and state machines. The layers were a reasonab

If I was revisiting, I'd probably eradicate the layer and pick a fixed number of flow types with distinct headers and state machines. The layers were a reasonable choice given the understanding of the time, but in hindsight I think you can make a strong case they're cut at the wrong places.