In data communications, the bandwidth-delay product is the product of a data link's capacity and its round-trip delay time. The result, an amount of data measured in bits, is equivalent to the maximum amount of data on the network circuit at any given time, i.e., data that has been transmitted but not yet acknowledged. The bandwidth-delay product was originally proposed as a rule of thumb for sizing router buffers in conjunction with congestion avoidance algorithm random early detection (RED).