[ns] TCP/Taho have strange result in NS2

[qadous@ccse.kfupm.edu.sa]

Dear ns-users,

I implement the Tahoe in ns2; I got strange values for its throughput.

The throughput in the Error rate =0 is less than the throughput in the Error
rate =0.01.

This is strange and opposite to expectations.
the code is below:

#Create a simulator object
set ns_ [new Simulator]

#Open the NAM trace file
set nf [open out.nam w]
$ns_ namtrace-all $nf
# open the Trace file
set tf [open out.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
         exit 0
}

#Create Two nodes
set s1 [$ns_ node]

set d1 [$ns_ node]

#Create link between the nodes
$ns_ duplex-link $s1 $d1 1.5Mb 10ms DropTail
#######################Error Model on the link
set loss_module [new ErrorModel]
$loss_module set rate_ 0.0
$loss_module ranvar [new RandomVariable/Uniform]
#$loss_module drop_target [new Agent/Null]
$ns_ lossmodel $loss_module $s1 $d1


#Set Queue Size of link (s2-r1) to 64 pckt
$ns_ queue-limit $s1 $d1 64

#Setup a TCP connection
set tcp1 [new Agent/TCP/Reno]
$ns_ attach-agent $s1 $tcp1
set sink1 [new Agent/TCPSink]
$ns_ attach-agent $d1 $sink1
$ns_ connect $tcp1 $sink1


#Setup a TCP connection(Tahoe)
set tcp2 [new Agent/TCP]
$ns_ attach-agent $s1 $tcp2
set sink2 [new Agent/TCPSink]
$ns_ attach-agent $d1 $sink2
$ns_ connect $tcp2 $sink2

#Setup a TCP connection
set tcp3 [new Agent/TCP/Newreno]
$ns_ attach-agent $s1 $tcp3
set sink3 [new Agent/TCPSink]
$ns_ attach-agent $d1 $sink3
$ns_ connect $tcp3 $sink3

#Setup a TCP connection
set tcp4 [new Agent/TCP/Sack1]
$ns_ attach-agent $s1 $tcp4
set sink4 [new Agent/TCPSink/Sack1]
$ns_ attach-agent $d1 $sink4
$ns_ connect $tcp4 $sink4

#Setup a FTP over TCP connection
set ftp1 [new Application/FTP]
$ftp1 attach-agent $tcp1
$ftp1 set type_ FTP

#Setup a FTP over TCP connection
set ftp2 [new Application/FTP]
$ftp2 attach-agent $tcp2
$ftp2 set type_ FTP

#Setup a FTP over TCP connection
set ftp3 [new Application/FTP]
$ftp3 attach-agent $tcp3
$ftp3 set type_ FTP

#Setup a FTP over TCP connection
set ftp4 [new Application/FTP]
$ftp4 attach-agent $tcp4
$ftp4 set type_ FTP


$tcp1 set packetSize_ 536 byte
$tcp2 set packetSize_ 536 byte
$tcp3 set packetSize_ 536 byte
$tcp4 set packetSize_ 536 byte

$tcp1 set window_ 128
$tcp2 set window_ 128
$tcp3 set window_ 128
$tcp4 set window_ 128


$tcp1 set tcpTick_ 0.5
$tcp2 set tcpTick_ 0.5
$tcp3 set tcpTick_ 0.5
$tcp4 set tcpTick_ 0.5

$ns_ at 0.0 "$ftp1 start";
$ns_ at 0.0 "$ftp2 start";
$ns_ at 0.0 "$ftp3 start";
$ns_ at 0.0 "$ftp4 start";


$ns_ at 49.9998 "$ftp1 stop";
$ns_ at 49.9998 "$ftp2 stop";
$ns_ at 49.9998 "$ftp3 stop";
$ns_ at 49.9998 "$ftp4 stop";



#$ns_ at 49.8013 "$s1 reset";
#$ns_ at 49.8013 "$d1 reset";


##########################################################
proc record {} {

global sink1 sink2 sink3 sink4 sink5 tcp1 tcp2 tcp3 tcp4

# get an instance of the simulater
set ns_ [Simulator instance]

#get the current time
set now [$ns_ now]

set bw1 [$sink1 set bytes_]
set bw2 [$sink2 set bytes_]
set bw3 [$sink3 set bytes_]
set bw4 [$sink4 set bytes_]

puts "compare when the flavors share the bottelneck"
puts "the goodput of Reno = [expr $bw1/$now * 8/1000]"
puts "the goodput of Taho = [expr $bw2/$now * 8/1000]"
puts "the goodput of Newreno = [expr $bw3/$now * 8/1000]"
puts "the goodput of Sack = [expr $bw4/$now * 8/1000]"

}

$ns_ at 49.999999 "record"
#Call the finish procedure after 11 seconds of simulation time
$ns_ at 50.0 "finish"
#Run the simulation
$ns_ run


I look forward to receive from you as soon as possible.


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