This read-write object, ranging from 1 to 100, configures the rate-fast-down value used by the card's rate control mechanism, presumably for a more aggressive rate reduction than the standard rate-down setting. An administrator would tune it to make the card respond more sharply to severe congestion signals. For example, an engineer dealing with a link prone to sudden severe congestion bursts might raise this value to force a faster rate cutback than rateDown alone would provide.