TCP Vegas RBP

RBP stands for Rate Based Pacing where it involves bandwidth estimation,clocking the segments,calculating the window and timing between the segments.
The detailed information can be got here
The implementation of RBP in NS2 is done using the following code:

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

set rbp [open RBP.tr w]

set tf [open mi.tr w]
$ns trace-all $tf

proc finish { } {
global ns nf tf
$ns flush-trace
close $nf
close $tf
exec nam mi.nam &
exit 0
}

set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]
$n3 label "destination"

$ns duplex-link $n0 $n2 10Mb 1ms DropTail
$ns duplex-link $n1 $n2 1Mb 100ms DropTail
$ns duplex-link $n2 $n3 1Mb 100ms DropTail


set tcp0 [new Agent/TCP/Vegas/RBP]
$ns attach-agent $n0 $tcp0

set ftp0 [new Application/FTP]
$ftp0 set packet_Size_ 500
$ftp0 set interval_ 0.005
$ftp0 attach-agent $tcp0

set tcp1 [new Agent/TCP/Vegas/RBP]
$ns attach-agent $n1 $tcp1

set ftp1 [new Application/FTP]
$ftp1 set packet_Size_ 1000
$ftp1 set interval_ 0.05
$ftp1 attach-agent $tcp1

set sink0 [new Agent/TCPSink]
$ns attach-agent $n3 $sink0

set sink1 [new Agent/TCPSink]
$ns attach-agent $n3 $sink1

$ns connect $tcp0 $sink0
$ns connect $tcp1 $sink1

$ns at 0.1 "$ftp0 start"
$ns at 0.1 "$ftp1 start"

  proc plotWindow {tcpSource file} {
     global ns

     set time 0.1
     set now [$ns now]
     set cwnd [$tcpSource set cwnd_]
     set wnd [$tcpSource set window_]
     puts $file "$now $cwnd"
     $ns at [expr $now+$time] "plotWindow $tcpSource $file"
  }

 $ns at 0.1 "plotWindow $tcp0 $rbp"


$ns at 10.0 "finish"
$ns run

Congestion is induced to see the behavior upon packet drop
The plot of congestion window versus time is as shown below