A method for controlling a bandwidth over a communication link connecting first and second client network elements. The first element is configured to send to the second element data traffic including at least a best effort traffic flow of packets. The method includes: at the first element, marking a number of best effort packets with a control code, the control code taking values within a predetermined ordered control sequence of values, and sending the marked packets to the second element through the link; at the second element, checking the control code of each marked best effort packet and, in case of detection of a missing value of the control code, sending to the first element a packet containing a feedback code indicative of an adjustment of the bandwidth; and, at the first element, upon reception of the feedback code, adjusting the bandwidth.