In this illustration, we see (from left to right): A server labeled "Video server" with a blue arrow pointing rightward from the server to a cloud representing the Internet. A blue arrow labeled "Fill rate = x" extends from the Internet to a large square, labeled "Client application buffer," that has been divided vertically into two sections. The entire square is labeled "B" and the right section is labeled "Q." In the left section, the first two-thirds are white while the last third is blue; the entire right section is blue. A blue arrow labeled "Depletion rate = r" extends rightward from the client application buffer.