limited queue

$ns queue-limit $n2 $n3 10
queue-limit is for limiting the number of queue.
In this code, there are 18 packets dropped in queue between node2 and node3.
We can check the number of dropped packets from tracing file and monitor-queue file which is generated by monitor-queue.

—————————
example4.tcl
—————————

#create a simulator object
set ns [new Simulator]

#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_example4.nam w]
$ns namtrace-all $nf

#Open the Trace file
set tf [open out_example4.tr w]
$ns trace-all $tf

#Define a finish procedure
proc finish {} {
global ns nf tf
$ns flush-trace
#Close the NAM trace file
close $nf
#close the trace file
close $tf
#Execute NAM on the trace file
exec nam out_example4.nam &
exit 0
}

#Create four nodes
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]

#color node
$n0 color blue
$n1 color red
$n2 color green

#Create links between the nodes
$ns duplex-link $n0 $n2 2Mb 10ms DropTail
$ns duplex-link $n1 $n2 2Mb 10ms DropTail
$ns duplex-link $n2 $n3 1.7Mb 20ms DropTail

#Color links
$ns duplex-link-op $n0 $n2 color “yellow”

#Set Queue size of link (n2-n3) to 10
$ns queue-limit $n2 $n3 10

#Give node position (for NAM)
$ns duplex-link-op $n0 $n2 orient right-down
$ns duplex-link-op $n1 $n2 orient right-up
$ns duplex-link-op $n2 $n3 orient right

#Monitor the queue for link (n2-n3) (for NAM)
$ns duplex-link-op $n2 $n3 queuePos 0.5

#Setup a TCP connection
set tcp [new Agent/TCP]
#$tcp set class_ 2
$ns attach-agent $n0 $tcp
set sink [new Agent/TCPSink]
$ns attach-agent $n3 $sink
$ns connect $tcp $sink
$tcp set fid_ 1

#Setup a FTP over TCP connection
set ftp [new Application/FTP]
$ftp attach-agent $tcp
$ftp set type_ FTP

#Setup a UDP connection
set udp [new Agent/UDP]
$ns attach-agent $n1 $udp
set null [new Agent/Null]
$ns attach-agent $n3 $null
$ns connect $udp $null
$udp set fid_ 2

#Setup cbr over UDP connection
set cbr [new Application/Traffic/CBR]
$cbr attach-agent $udp
$cbr set type_ CBR
$cbr set packet_size_ 1000
$cbr set rate_ 1mb
$cbr set random_ false

#tracing queue in node2
set qm [$ns monitor-queue $n2 $n3 [open qm4.out w] 1];
[$ns link $n2 $n3] queue-sample-timeout; #start tracing

#Schedule events for the CBR and FTP agents
$ns at 0.1 “$cbr start”
$ns at 1.0 “$ftp start”
$ns at 4.0 “$ftp stop”
$ns at 4.5 “$cbr stop”

#Detach tcp and sink agents (not really necessary)
$ns at 4.5 “$ns detach-agent $n0 $tcp ; $ns detach-agent $n3 $sink”

#Call the finish procedure after 5 seconds of simulation time
$ns at 5.0 “finish”

#Print CBR packet size and interval
puts “CBR packet size = [$cbr set packet_size_]”
puts “CBR interval = [$cbr set interval_]”

#Run the simulation
$ns run

—————————

Result in qm4.out

0 2 3 0 0 0 0 0 0 0 0
1 2 3 0 0 111 111 0 111000 111000 0
2 2 3 3523.9871999997463 3.4610635294115144 319 301 12 321320 303000 12240
3 2 3 4315.5418352945644 4.2457694117651528 527 503 16 532640 508080 16400
4 2 3 4193.1512470598409 4.1231811764715989 731 705 18 739800 713240 18400

the total number of dropped packet is 18 and the total size of dropped packets is 18400 Bytes.

Trace File :

……..
d 1.337868 2 3 tcp 1040 ——- 1 0.0 3.0 26 193
….
d 3.954 2 3 cbr 1000 ——- 2 1.0 3.1 480 944
……..

the number ‘d’ (drop) mark is 18.
How to differentiates between tcp dropped and cbr dropped ? use awk to filter ?

NAM Trace File :

Chinese Song : Dream Pursuer

May 13, 2008
Taipei City
High Speed Network Lab

Udin Harun

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