[ns] monitor packets drops

["Michele R." <mic.rus@libero.it>]

 

Hello!

I've a link between two router,n3 and n4,and I'd like to monitor packets which are drops for each flow 1, 2 and 3 that arrives at the roter n3.

 

I would like to use:  

.............................

    set counter [$ns makeflowmon Fid]           
    set bottleneck [$ns link $n3 $n4]       
    $ns attach-fmon $bottleneck $counter        

    set flowClassifier [$counter classifier]

 

    set flow [$flowClassifier lookup auto 0 0 1]
    set tcp0share [$flow set pdrops_]
    set tcp0bw [expr $tcp0share - $tcp0bw]

 

    set flow [$flowClassifier lookup auto 0 0 2]
    set tcp1share [$flow set pdrops_]
    set tcp1bw [expr $tcp1share - $tcp1bw]

 

    set flow [$flowClassifier lookup auto 0 0 3]
    set tcp2share [$flow set pdrops_]
    set tcp2bw [expr $tcp2share - $tcp2bw]

..................................

but it doesn't work because of "the presence of pdrops_"?

 why?

Can you help me?

if I put "set p_departures" it works! (but so I only count the packets departure for each flow..)

thank you.