Re: [ns] Monitoring the queue size

[Felix Hernandez Campos <fhernand@cs.unc.edu>]

Marta Solera wrote:

> Hi all,
>
> but i don't know how to monitor the queue size or the number of packets
> drops.
>

Hi,

Here you have an easy way of doing that:

###

# monitor the queue that buffers packets going from node n1 to node n2
set qmon [$ns monitor-queue $n1 $n2 0]

# queue size trace
set fqsize [open "qsize.n1-n2.out" w]

# no. of drops trace
set fqdrop [open "qdrop.n1-n2.out" w]

$ns at 0 "record"

proc record {} {
    global ns qmon fqsize fqdrop

    set time  [$ns now]
    set qsize [$qmon set pkts_]
    set qdrop [$qmon set pdrops_]

    puts $fqsize "$time $qsize"
    puts $fqdrop "$time $qdrop"
    $qmon reset

    # stats every 1 second
    $ns at [expr $time+1.0] "record"
}

proc finish {} {
    global fqsize fqdrop
    ...
    close $fqsize
    close $fqdrop
    ...
}

###

Since you were trying to use "queue-sample-timeout", I assumed you wanted to
collect queue size and no. of drops at regular intervals. If what you want
is to collect all the changes, you'll have to use "trace-queue" and
post-process the trace.

Regards,

--
Felix Hernandez Campos
http://www.cs.unc.edu/~fhernand