Layer 3 fair rate congestion control notification

An apparatus comprising:

• multiple ports configured to receive/send data packets from/to a network;
• and
• a processor coupled to the ports and configured to:
• receive data packets of multiple traffic flows and populate a queue with the data packets;
• periodically update a fair rate to be applied to ones of the multiple traffic flows to converge a length of the queue to a reference length over time such that the processor is configured to:
• measure a length of the queue, compute a change in the length from a previous length, and compute a deviation of the length from the reference length;
• detect an increase in the change in the length above at least one threshold that is based on the reference length;
• and
• if the increase is not above the at least one threshold, and if the deviation of the length of the queue from the reference length indicates that the length of the queue is less than or above the reference length, derive the fair rate from a previous fair rate using proportional integral control based on tunable control parameters by respectively increasing or decreasing the previous fair rate by an amount that is equal to a sum of (i) a product of a first tunable control parameter and the deviation of the length of the queue from the reference length, and (ii) a product of a second tunable control parameter and the change in the length of the queue from the previous length of the queue, to produce the fair rate;
• periodically identify elephant flows among the multiple traffic flows;
• and
• periodically send the fair rate to a source of each elephant flow.

A non-transitory computer readable medium encoded with instructions that, when executed by a processor of a network switch or router having multiple ports configured to receive/send data packets from/to a network, cause the processor to perform:

• receiving data packets of multiple traffic flows and populating a queue in memory with the data packets;
• periodically updating a fair rate to be applied to ones of the multiple traffic flows to converge a length of the queue to a reference length over time, the updating including:
• measuring a length of the queue, computing a change in the length from a previous length, and computing a deviation of the length from the reference length;
• detecting an increase in the change in the length above at least one threshold that is based on the reference length;
• and
• if the increase is not above the at least one threshold, and if the deviation of the length of the queue from the reference length indicates that the length of the queue is less than or above the reference length, deriving the fair rate from a previous fair rate using proportional integral control based on tunable control parameters by respectively increasing or decreasing the previous fair rate by an amount that is equal to a sum of (i) a product of a first tunable control parameter and the deviation of the length of the queue from the reference length, and (ii) a product of a second tunable control parameter and the change in the length of the queue from the previous length of the queue, to produce the fair rate;
• periodically identifying elephant flows among the multiple traffic flows;
• and
• periodically sending the fair rate to a source of each elephant flow.