[ns] queue drop-target

[// u l i a n <waldby@uiuc.edu>]

I am using a visible queue with a drop target in ns 2.1b5. I am finding
the queue seemingly growing to huge sizes (900 when I have specified 80
as the limit_). I believe that packets dropped from the queue are
remaining in the pictorial view of the queue. Can someone help me with
this problem? Here are the relevant lines of code:

set n2 [$ns node]
set n3 [$ns node]

$ns simplex-link $n2 $n3 100kB 300ms DropTail
$ns simplex-link-op $n2 $n3 queuePos -0.05

set dropQ [new Agent/TackDrop]
set bottleQ [[$ns link $n2 $n3] queue]
$bottleQ set limit_ 80
$bottleQ drop-target $dropQ

I have a couple other queues set which shouldn't be interfering:

set Q0 [[$ns link $n0 $n2] queue]
$Q0 set limit_ 800

set Q1 [[$ns link $n1 $n2] queue]
$Q1 set limit_ 800

I tried setting these two queues much smaller, say around 200, and the
bottleQ was still showing around 900 packets.

Other strange things are happening with this queue that are probably
related. I have a red and blue flow coming into the queue. There are
times when red packets are the next available packets and instead, blue
packets appear on the link.

Thanks for any help.

Julian Waldby