This illustration reuses the image from figures 4.2 and 4.3, in which we see a series of routers arranged in a pentagram and connected with black lines representing interface links. Each router is associated with a forwarding table, and each forwarding table is informed by a routing algorithm. A dotted horizontal line separates the control plane (above the line) from the data plane (below the line); the routing algorithm originates in the control plane and sends its information to the forwarding table in the data plane. Further, the routing algorithms for each forwarding table interact with each other, depicted here as a web of blue arrows connecting all the algorithms together.