During a Transmission Control Protocol (“TCP”) session, a sending endpoint computer monitors amounts of data sent and patterns of data loss as data is sent to a receiving endpoint computer. The sending endpoint computer periodically determines whether data is being sent below, at or above path capacity, based on the monitored amounts of data sent and patterns of data loss observed. The sending endpoint computer periodically dynamically adjusts the rate at which data is sent to the receiving endpoint computer, in response to the determinations whether data is being sent below, at or above path capacity.