hello, I reckon up the loss packet by awk file, the result is quite different of the result of printing form mac-802_11.cc. Could you please give me some advices? In 802_11.cc, when receive a ACK(recvACK()), recv_packet will be added by one; when RetransmitDATA() was called, the loss packet will be added by one. The result is send packet:8067, loss packet: 224. when I use the awk file, which is attached, to do the same work in tracefile. The sending packets is 48016 and recv_pkt is 3848, which means loss packets is 48016-3848=44168. However, I can't find any Drop line in the trace file. They are quite different but which one is right? Thanks for your help! (There are only 2 nodes in my simulation) EGIN { sendLine = 0; recvLine = 0; } $0 ~/^s.* AGT/ { sendLine ++ ; } $0 ~/^r.* AGT/ { recvLine ++ ; } $0 ~/^D.* AGT/ { lossLine ++ ; } END { printf "send pkt:%d recv pkt :%d, r/s Ratio:%f, losspkt: %d, NRL: %f \n", sendLine, recvLine, (recvLine/sendLine),lossline; }