Re: [ns] Packets lost

[Xuan Chen <xuanc@ISI.EDU>]

Why not run TCP with FTP traffic, since you've already attached them? It
is hard for me to understand the purpose to put CBR and TCP together...

-chen xuan

On Thu, 21 Jun 2001, Qingjuan Gu wrote:

> Hello everybody,
>
> I am using TCP agent, and FTP application to do simulation.
> node n0, n1 and n2.
>
> n0 ---------------- n1 -----------n2
>        10Mb		  1Mb
>
> I set the queue limit is 10:
> $ns queue-limit $n1 $n2 10
>
> I send data from node n0:
> $cbr0 set packetSize 500
> $cbr0 set interval_ 0.0001
>
> but according to the trace file, there are only 3 packets lost. I can not
> understand this? does anybody explain or give me some advice?
>
> Thank you very much.
>
> Appending my simple script:
>
> set ns [new Simulator]
> # initialise the simulation
> # Predefine tracing
> set f [open out.tr w]
> $ns namtrace-all $f
>
> set n0 [$ns node]
> set n1 [$ns node]
> set n2 [$ns node]
> $ns duplex-link $n0 $n1 10Mb 10ms DropTail
> $ns duplex-link $n1 $n2 1Mb 20ms DropTail
> $ns queue-limit $n1 $n2 10
>
> # A FTP over TCP from $n1 to $n2
> set tcp [new Agent/TCP]
> $ns attach-agent $n0 $tcp
> set sink [new Agent/TCPSink]
> $ns attach-agent $n2 $sink
> set ftp [new Application/FTP]
> $ftp attach-agent $tcp
> set cbr0 [new Application/Traffic/CBR]
> $cbr0 attach-agent $tcp
> $cbr0 set packetSize 500
> $cbr0 set interval_ 0.0001
> $ns connect $tcp $sink
>
> $ns at 0.1 "$cbr0 start"
> $ns at 1.35 "$ns detach-agent $n0 $tcp ; $ns detach-agent $n2 $sink"
> $ns at 3.0 "finish"
> proc finish {} {
> global ns f
> $ns flush-trace
> close $f
> #close $nf
> puts  "running nam..."
> exec nam out.nam &
> exit 0 }
> $ns run
>

-- 
Xuan Chen
USC/ISI