Optimum utilization of yellow tokens in packet metering

A packet metering circuit configured to optimize utilization of yellow tokens, the packet metering circuit comprising:

• circuitry configured to receive a packet of size B in an interval;
• and
• a meter, implemented in circuitry, configured to mark a color of the packet as green for committed, yellow for excess, or red for discard, based on the size B, a current committed token bucket for the interval, a current excess token bucket, and an overflow counter used to preserve unused yellow tokens from previous intervals while preserving Excess Information Rate (EIR) and Excess Burst Size (EBS) for the interval;
• wherein the meter operates in a color-aware mode, and wherein the meter is configured to
• when the packet is a green packet at time t, then
• if the current committed token bucket minus B is greater than 0, mark the packet as green, and decrement the current committed token bucket by B;
• else
• if the current excess token bucket minus B is greater than or equal to 0, mark the packet as yellow, and decrement the current excess token bucket by B;
• else
• if the current excess token bucket plus the overflow counter is greater than B and if the EBS is greater than or equal to B, mark the packet as yellow and decrement the overflow counter by B minus the current excess token bucket and the current excess token bucket is set to 0;
• else
• mark the packet as red;
• when the packet is a yellow packet at time t, then
• if the current excess token bucket minus B is greater than 0, mark the packet as yellow, and decrement the current excess token bucket by B;
• else
• if the current excess token bucket plus the overflow counter is greater than B and if the EBS is greater than or equal to B, mark the packet as yellow and decrement the overflow counter by B minus the current excess token bucket and the current excess token bucket is set to 0;
• else
• mark the packet as red.

A packet switch configured to optimize utilization of yellow tokens, the packet switch comprising:

• one or more line ports;
• and
• a meter configured to, responsive to receipt of a packet of size B in an interval, mark a color of the packet as green for committed, yellow for excess, or red for discard, based on the size B, a current committed token bucket for the interval, a current excess token bucket, and an overflow counter used to preserve unused yellow tokens from previous intervals while preserving Excess Information Rate (EIR) and Excess Burst Size (EBS) for the interval;
• wherein the meter operates in a color-aware mode, and wherein the meter is configured to
• when the packet is a green packet at time t, then
• if the current committed token bucket minus B is greater than 0, mark the packet as green, and decrement the current committed token bucket by B;
• else
• if the current excess token bucket minus B is greater than or equal to 0, mark the packet as yellow, and decrement the current excess token bucket by B;
• else
• if the current excess token bucket plus the overflow counter is greater than B and if the EBS is greater than or equal to B, mark the packet as yellow and decrement the overflow counter by B minus the current excess token bucket and the current excess token bucket is set to 0;
• else
• mark the packet as red;
• when the packet is a yellow packet at time t, then
• if the current excess token bucket minus B is greater than 0, mark the packet as yellow, and decrement the current excess token bucket by B;
• else
• if the current excess token bucket plus the overflow counter is greater than B and if the EBS is greater than or equal to B, mark the packet as yellow and decrement the overflow counter by B minus the current excess token bucket and the current excess token bucket is set to 0;
• else
• mark the packet as red.