A method for evaluating an available bitrate over a path among one of at least two paths linking a first endpoint and a second endpoint, the path being called an evaluation path, is disclosed. The first endpoint is configured for sending data packets to the second endpoint, the second endpoint is configured for sending at each data packet reception an acknowledgment message to the first endpoint through one of the at least two path selected at each data packet reception. The method comprises, at the first endpoint, steps of: inserting a flag in a first data packet out of the data packets to be transmitted to the second endpoint through the evaluation path; sending said first data packet through the evaluation path; measuring and recording a sending time of the first data packet from said first endpoint; receiving an acknowledgment message sent by the second endpoint through the evaluation path for acknowledging reception of the first data packet at said second endpoint; measuring and recording an arrival time of said acknowledgment message at said first endpoint; assessing the available bitrate from an interval between the sending time and the arrival time and from the size of said first data packet. A method for sending at a second endpoint an acknowledgement message over a path among one of at least two paths linking a first endpoint and said second endpoint is further disclosed. Associated device for evaluating an available bitrate and device for sending at a second endpoint an acknowledgement message are disclosed.