The present invention provides a system and method for prioritizing delay-sensitive packets relative to each other for transmission from a router in a network, based on a delay variation estimated for each delay-sensitive packet by a quality of service monitor. In accordance with the present invention, late delay-sensitive packets are assigned a higher priority than, and are transmitted before, other delay-sensitive packets, thereby reducing the level of jitter and improving the quality of the packet streams that comprise late delay-sensitive packets.