In one example, the encoding rate at which data is delivered over a network is estimated by intercepting a data packet from a data streaming session, wherein the data packet contains at least a portion of one of a plurality of file segments containing portions of a file, and wherein a number of the plurality of file segments that is delivered via the data streaming session is limited to a maximum number. The mean size of the plurality of file segments is estimated from data contained in the data packet. A plurality of potential sizes of the plurality of file segments is calculated, wherein each potential size corresponds to one number between one and the maximum number. An encoding rate of the data streaming session is calculated, based at least in part on which potential size of the plurality of potential sizes is closest to the mean size.