[ns] how to trace only droped packets?

[Fengyun Cao <fcao@CS.Princeton.EDU>]

Hi all,
	This is my first question here :)
	I'm using UPD in my ns, so packets may be dropped, and that really
concerned me. So I have to use "trace-all" and then to check for dropped
packets in trace file. But when program grows big, the trace file grows so
big that I/O buffer is crashed :( 
	What shall I do, to detect any dropped packets, yet avoid
generating too much useless trace data?


Thanks a lot!

Fengyun