Hi, I'm trying to use the Queue monitor to print out the queue size on a link every 0.1 seconds.... I have the following code in my script file: set fm2 [open all2.fm w] set qmon [$ns monitor-queue $n2 $n3 $fm2] I'm just beginning with Tcl, is there something else I need to do? The output file is empty... Thanks for any help, Chris