Hi , I have this configuration (SS-Wimax Subscriber Station and BS-Wimax Base Station)): (PC1)----100mbs---(SS)----3mbs----(BS)----100mbs----(PC2) When i measure the RTT with the ping command from the PC1 to the PC2, i'm measuring approximately the packet service time of the station SS = 1/u2, and also the time of the BS when the reply comes, that can be more or less 1/u2. The time of processing from the computers in not significant. If i use iperf to send a flow of 6mbs from the PC1 to the PC2, the Wimax queue of the SS will built up and if i run the ping command with the same packet size, and with 1 second of interval (that is not significant when compared to the iperf), the time of processing of the SS=X.(1/u2) because the packet sent by ping will reach the last place of the queue. When it return has 1/u2 additional from the BS. So if I divide, I'll get X, that is approximately the queue size of the SS. Do you think that it gives a notion about the size of the buffer of the SS? By the way, i didn't use thrulay, because the delay is high, maybe because of the time synchronization between the PC1 and PC2. Is easy to synchronize the both computers, having one as server and another receiving the synchronization? kindly, and thanks for the precious help given Tiago Junqueira