[ns] Where to find the defination of the procedure cmu-trace??

[Xia Xin]

Hi all:

	in the file ns-mobilenode.tcl, there is always a function call cmu-trace 

		#
		# Trace Sent Packets
		#
		if {$imepflag != ""} {
			set sndT [$self mobility-trace Send "MAC"]
		} else {
			set sndT [cmu-trace Send "MAC" $self]
		}
	but I cannot find the defination of the procedure cmu-trace in all the tcl scripts.Can anyone give me some help?