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LAN routing ?



Hello,

 I have some problems with LAN routing.  I use ns-allinone-2.1b5.
 I run ns on SunOS 5.6 (Solaris).

 My test configuration is as follows:
 
  na    nb
  |     |
  n0    n2
  |     |
  +-----+
  |     |
  n1    n3

 Here n0,n1,n2,n3 are nodes in a 802_3 LAN.
 na and nb are external nodes which interact with nodes inside the LAN.
 I want to have three ftp traffic flows:  n0->nb, nb->n1 and nb->na.
       
 The problem is that the only traffic flow that gets through 
 in both directions (data/ack) was  nb->n1 (as seen from nam --
 you may try to diable the 'start' statement of each ftp flow 
 and see the result).

 The script for the simulation is given below

 Is there any routing statement I should add to the script ?
 or is it a bug ? or is it a problem with my own ns build  ?

Thanks,
Apinun.


== cut here ==

set ns [new Simulator]
set f [open out.nam w]
$ns namtrace-all $f

set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]

set nodelist_ "$n0 $n1 $n2 $n3"

set na [$ns node]
set nb [$ns node]

$ns duplex-link $na $n0  10Mb 20ms DropTail
$ns duplex-link $nb $n2  10Mb 20ms DropTail

$ns duplex-link-op $na $n0 orient down
$ns duplex-link-op $nb $n2 orient down

set lan_ [$ns make-lan $nodelist_ 10Mb 1ms LL Queue/DropTail Mac/802_3 Channel]

$ns compute-routes

set tcp0 [$ns create-connection TCP/Reno $n0 TCPSink $nb 0]
set tcp1 [$ns create-connection TCP/Reno $nb TCPSink $n1 1]
set tcp2 [$ns create-connection TCP/Reno $nb TCPSink $na 2]

$tcp0 set window_ 128
$tcp1 set window_ 128
$tcp2 set window_ 128

set ftp0 [$tcp0 attach-app FTP]
set ftp1 [$tcp1 attach-app FTP]
set ftp2 [$tcp2 attach-app FTP]

$ns at 0.1 "$ftp0 start"
$ns at 0.2 "$ftp1 start"
$ns at 0.3 "$ftp2 start"

$ns at 30.0 "$ns halt"
puts "running..."
$ns run

puts "finishing..."
$ns flush-trace
close $f

== cut here ==