DV routing

["Lara Pajewski" <lpajewski@hotmail.com>]

Dear All,
we have a problem with DV routing:
we have defined four nodes and told the simulator to use dynamic 
routing.
There is a CBR agent attached to n0 and a Null agent attached to n3.
Simulation time is 5.0 seconds. Changing the cost of the duplex-link 
between n0 
and n3 at 2.5, we expect the routing to be updated and the traffic to be 
re-routered 
through the nodes n1 and n2.
The Tcl script (you can see it below) doesn't contain syntax errors, but 
the packets 
aren't re-routered. Which is a correct way to change the cost of a link 
at a 
certain moment of the simuation?
   


set ns [new Simulator]
set nf [open out.nam w]
$ns namtrace-all $nf

proc finish {} {
        global ns nf
        $ns flush-trace
        close $nf
        exec nam out.nam &
        exit 0 }
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]

$ns duplex-link $n0 $n1 1Mb 10ms DropTail
$ns cost $n0 $n1 2
$ns cost $n1 $n0 2
$ns duplex-link $n1 $n2 1Mb 10ms DropTail
$ns cost $n1 $n2 1
$ns cost $n2 $n1 1
$ns duplex-link $n2 $n3 1Mb 10ms DropTail
$ns cost $n2 $n3 5
$ns cost $n3 $n2 5
$ns duplex-link $n3 $n0 1Mb 10ms DropTail
$ns cost $n0 $n3 1
$ns cost $n3 $n0 1

$ns rtproto DV

set cbr0 [new Agent/CBR]
$ns attach-agent $n0 $cbr0

set null3 [new Agent/Null]
$ns attach-agent $n3 $null3

$ns connect $cbr0 $null3


$ns at 1.0 "$cbr0 start"

#We have doubts about the next line!!!!!!
$ns at 2.5 "$ns cost $n0 $n3 100"

$ns at 5.0 "finish"

$ns run 


Thanks in advance, bye, Lara.
        


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