The present disclosure describes a method for characterizing a maximum frame size in a network data transmission with a feedback loop. A source device transmits a set of current frames with an initial frame size to a designation device, and receives returning frames from the designation device via a loopback interface. The frame size of subsequent frames to be transmitted is adjusted in bytes. The adjustment of the frame size may be based on a predetermined condition related to the returning frames. The maximum value of the frame size satisfied with the predetermined condition may be designated as the maximum frame size. A plurality of algorithms and machine learning may be used to project the frame size of the subsequent frames and obtain a precise value of the maximum frame size in a network route.