bandwidth delay product

BDP -- Bandwidth Delay Product.

In data communications, bandwidth-delay product refers to the 
product of a data link's capacity (in bits per second) and its
 end-to-end delay (in seconds). The result, an amount of data
 measured in bits (or bytes), 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 received. Sometimes it is calculated
 as the data link's capacity times its round trip time

source : Wikipedia.