I want to create and simulate a wired topology using NS2. Trying to write a tcl and positioning the nodes and links using rand() . My solution was:
### Create a simulator object
set ns [new Simulator]
set num_node 10
set num_flow 5
set x_dim 150
set y_dim 150
### Define different colors for data flows (for NAM)
$ns color 1 Blue
$ns color 2 Red
### Open the NAM trace file
set nf [open out.nam w]
$ns namtrace-all $nf
set tracefd [open out.tr w]
$ns trace-all $tracefd
### set up topography object
set topo [new Topography]; # This is needed for wireless
$topo load_flatgrid $x_dim $y_dim; # Setting a 2D space for the nodes
### Define a 'finish' procedure
proc finish {} {
global ns nf tracefd
$ns flush-trace
### Close the NAM trace file
close $nf
close $tracefd
### Execute NAM on the trace file
exec nam out.nam &
exit 0
}
#Create four nodes
for {set i 0} {$i < [expr $num_node]} {incr i} {
set n($i) [$ns node]
puts "Created node $i"
}
### Create links between the nodes
for {set i 0} {$i < [expr $num_node + 1]} {incr i} {
set s_node [expr int($num_node*rand())]; # src node
set d_node $s_node
while {$d_node==$s_node} { ; # while the random pair are same node
set d_node [expr int($num_node*rand())]; # dest node
}
$ns duplex-link $n($s_node) $n($d_node) 2Mb 10ms DropTail
$ns queue-limit $n($s_node) $n($d_node) 50
puts "Linking $s_node and $d_node"
}
### Give node position (for NAM)
set i 0
while {$i < $num_node } {
### Set random position for nodes
set x_pos [expr int($x_dim*rand())]; # random settings
set y_pos [expr int($y_dim*rand())]; # random settings
$n($i) set X_ $x_pos
$n($i) set Y_ $y_pos
$n($i) set Z_ 0.0
puts "Put $i to ($x_pos , $y_pos)"
#puts -nonewline $topofile "$i x: [$node_($i) set X_] y: [$node_($i) set Y_] \n"
incr i;
};
### Setup UDP connections
for {set i 0} {$i < [expr $num_flow]} {incr i} {
set s_node [expr int($num_node*rand())]; # src node
set d_node $s_node
while {$d_node==$s_node} {; # while the random pair are same node
set d_node [expr int($num_node*rand())]; # dest node
}
set udp($i) [new Agent/UDP]
$udp($i) set class_ $i
$ns attach-agent $n($s_node) $udp($i)
set null($i) [new Agent/Null]
$ns attach-agent $n($d_node) $null($i)
$ns connect $udp($i) $null($i)
$udp($i) set fid_ $i
puts "Flow $s_node - $d_node"
}
### Setup a CBR over UDP connections
for {set i 0} {$i < [expr $num_flow]} {incr i} {
set cbr($i) [new Application/Traffic/CBR]
$cbr($i) attach-agent $udp($i)
$cbr($i) set type_ CBR
$cbr($i) set packet_size_ 1000
$cbr($i) set rate_ 1mb
$cbr($i) set random_ false
puts "setting cbr for $i"
}
### Schedule events for the CBR and FTP agents
for {set i 0} {$i < [expr $num_flow]} {incr i} {
$ns at 0.1 "$cbr($i) start"
}
for {set i 0} {$i < [expr $num_flow]} {incr i} {
$ns at 4.5 "$cbr($i) stop"
}
for {set i 0} {$i < [expr $num_node] } { incr i} {
$ns initial_node_pos $n($i) 4
}
### Run the simulation
$ns run
But the randomization is often creating erroneous links and thus problem in simulation and getting this error :
--- Classfier::no-slot{} default handler (tcl/lib/ns-lib.tcl) --- _o28: no target for slot 4294967295 _o28 type: Classifier/Hash/Dest content dump: classifier _o28 0 offset 0 shift 1073741823 mask 1 slots slot 5: _o268 (Classifier/Port) -1 default ---------- Finished standard no-slot{} default handler ----------
But this is also random and does not occur always. When it does not occur , the nam file shows that there have been duplicate definition of nodes. Can someone please just give me some guidance about how to create a random wired topology with random valid links?