A method is intended for computing online channel loss rate and collision loss rate of at least one communication link established between nodes (N1, N2) of a network (WN) using a random access MAC protocol. This method comprises the steps of i) dividing time in probing windows and transmitting a chosen number S of probe packets during each probing window from a transmitter node (N1) to a receiver node (N2) linked therebetween, ii) measuring a packet loss rate from probe packets lost on this communication link during a probing window, iii) scanning each probing window with smaller sliding windows, each having a size Wk smaller than S, to identify the sliding window during which only channel losses occur, and then for computing a channel loss rate on this communication link from this identified sliding window, and iv) computing a collision loss rate on this communication link by subtracting the computed channel loss rate from the measured packet loss rate.