an integrated circuit monitors the most active traffic flow rates on a communications network by using a leaky bucket model having a variable fill rate . as a switch receives packets , the packet identifications are sampled . a sampled packet identification is compared to record identifications in a table of identifications . if the sampled and record identifications match , an activity value for the packet identification is increased by an amount inversely proportional to an activity value associated with the record identification . if the sampled and record identifications do not match , the activity value is decreased . record identifications are removed from the table when the activity value decreases to a specified level . new sampled identifications are added to the table if empty records exist .