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# pkts.tcl
# This script tries to simulate a scnenario involving very large number
# of packets on the fly so that we can get an idea of the memory usage
# due to heavyweight pkt-hdrs in every pkt.
# Dmalloc has been used to measure memory consumption for this
# experiment.
# With all pkt-headers (default condition in ns) memory consumption
# is ~140MB. with total pkts on the fly at around 60,000, (using cbr
# pktsize of 210, linkBW of 1Gb, delay of 100ms),
# memory consmp. ~2KB/pkt.
# With (unused) pkt headers removed, memory usage is ~30Mb and the
# figure for per pkt comes down to ~500bytes
# which is a considerable gain (about 75% reduction of memory use).
# add/remove packet headers as required
remove-all-packet-headers ;# removes all except common
add-packet-header IP Message ;# hdrs reqd for cbr traffic
#add-packet-header Flags IP TCP ;# hdrs reqd for TCP
#setting CBR rate to 1Gb to match the link BWrate
Application/Traffic/CBR set rate_ 1000Mb
set ns [new Simulator]
set linkBW 1000Mb
set delay 100ms
set n0 [$ns node]
set n1 [$ns node]
set f [open pkts.tr w]
$ns trace-all $f
#set nf [open pkts.nam w]
#$ns namtrace-all $nf
$ns duplex-link $n0 $n1 $linkBW $delay DropTail
#set tcp0 [new Agent/TCP]
set udp0 [new Agent/UDP]
$ns attach-agent $n0 $udp0
#set ftp0 [new Application/FTP]
set cbr0 [new Application/Traffic/CBR]
$cbr0 attach-agent $udp0
#set sink0 [new Agent/TCPSink]
set null0 [new Agent/Null]
$ns attach-agent $n1 $null0
$ns connect $udp0 $null0
$ns at 0.2 "$cbr0 start"
$ns at 1.0 "finish"
proc finish {} {
global ns f nf
$ns flush-trace
close $f
#close $nf
puts "running nam.."
exec nam pkts.nam &
exit 0
}
$ns run
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