This illustration uses two images to describe RDT from both the sender and the receiver. In the first, a black arrow extends diagonally downward and from left to right, pointing to a blue circle labeled "Wait for call from above." A blue arrow extends from the upper right side of this circle, travels in a clockwise motion and points back to the lower right side of the same circle. This blue arrow has two labels with a horizontal line separating them. on top: "rdt_send (data)," and on the bottom: "packet=make_pkt (data)

udt_send (packet)"

The second image is identical to the first, except for small variations in the labeling. The blue circle here is labeled "Wait for call from below." And the blue arrow is labeled: "rdt_rcv (packet)" and "extract (packet, data)

deliver_data (data)"