[ns] Other Trace variables - T_RTT

[Justin]

Hello all, yet again.   :)

I mentioned in my earlier post about one of my output files only having 
one line in it (for rtt_).  Well, I have tried again with another 
variable and it also has only one line in it.  What's going on?  Here's 
the one line:

0.00000  -1 -1 -1 -1 t_rtt_ 0

Here's the TCL:

for {set j 1} {$j<=$NumbSrc} {incr j} {
     set tcp_src($j) [new Agent/TCP/Reno]
     $tcp_src($j) set window_ 256
     $tcp_src($j) set fid_ $j

     #Trying a new variable to trace:  T_RTT_
     set t_rtt_trace [open "t_rtt.tr" w];
     $tcp_src($j) attach $t_rtt_trace;
     $tcp_src($j) tracevar t_rtt_;                # trace t_rtt

     # tracing TCP congestion window variables
     set cwnd_trace [open "cwnd_.trace" w];
     $tcp_src($j) attach $cwnd_trace;
     $tcp_src($j) tracevar cwnd_;              # trace cwnd (which also 
tracks RTT?)
}

The trace on CWND_ comes out just fine, I think.  (Yeah, see previous 
messages on that, too.)

Thanks,
J