In this image, a large square divided into two sections is used to illustrate the receive window and receive buffer. A vertical line divides the square into about one section of about two-thirds the size of the whole, and one section about one-third the size of the whole. The bigger, left-hand portion of the square is labeled "Spare room." This portion is indicated as "rwnd." The smaller, right-hand portion is shaded in gray and labeled "TCP data in buffer." The entire square is indicated as "RcvBuffer."

A blue arrow points from left to right towards the left side of this square, and is labeled "Data from IP." A second blue arrow points from left to right away from the right side of this square, and is labeled "Application process."