a method , system , and product are described for alleviating router congestion when the router is processing packets transmitted by computer systems having a congestion notification capability . the router marks packets transmitted between a first computer system and a second computer system when the first and second computer systems have the congestion notification capability . the marking indicates that the router is moderately congested . a marked packet is then received by the first computer system . the router then drops packets transmitted by the first computer system when the packets were transmitted subsequently to the receipt of the marked packet .