A system, apparatus, and method are directed towards managing traffic over a network by imposing temporal delays in acknowledgments (ACKs). A Traffic Management Device (TMD), interposed between two network session end-points monitors a buffer of relayed packets. If the contents of the buffer exceed a threshold value, delays are imposed on sending of acknowledgements. If the buffer contents exceed the threshold, and the buffer's contents are increasing, the delays may be increased. If the buffer's contents are about at steady state, the acknowledgement delays may be decreased, or maintained at a current delay status. In one embodiment, if the sender is sending packets at a rate above a receiver's ability to receive the packets, and the sender appears not to be decreasing its rate of transmission, an explicit congestion notification echo (ECE) may be sent to the sender.