In this illustration, we see a desktop computer at top left shaded in blue connected to a series of routers by a line that slopes diagonally downward to the right. There are four routers, all shaded blue. The first router also connects to a computer, shaded gray. The second router connects to a router on the left, shaded gray, which connects to two computers, also shaded gray. This second router also connects to a router on the right, shaded gray. These two gray routers connect with the third blue router as well. The fourth router connects to two computers, one gray and one blue. A blue arrow, labeled "QoS call signaling setup," begins in the top left computer and travels down the slope through each of the blue routers. As it passes each router, we see smaller blue arrows pointing from the arrow to the router and from the router to the arrow, and these are labeled "Request/reply." The blue arrow passes through all four blue routers and into the blue computer connected to the fourth blue router.