[ns] BST multicast routing behaviour

[Andrea Josi <mr_josi@yahoo.it>]

Hi,

in this topology

        n0---------n1----------n2

let n2 be the RP for the multicast group "group0": 

when n1 joins to group0, a graft will be sent from n1
to n2; if then n0 joins, its graft is sent to n1 which
doesn't forward it to n2

on the contrary:
if it is n0 to join first, its graft will reach n2
passing through n1; if then n1 joins, it sends a graft
to n2 even if not necessary (in my opinion...)!!! why
?
is this a correct behaviour ?

Thanks a lot,

                 Andrea.

Here is the script 


set ns [new Simulator -multicast on]

set f [open aj/bst1.tr w]
$ns trace-all $f
$ns namtrace-all [open aj/bst1.nam w]

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

$ns duplex-link $n0 $n1 1.5Mb 10ms DropTail
$ns duplex-link $n1 $n2 1.5Mb 10ms DropTail

set group0 [Node allocaddr]

BST set RP_($group0) $n2
$ns mrtproto BST

set rcvr0 [new Agent/LossMonitor]
$ns attach-agent $n0 $rcvr0

set rcvr1 [new Agent/LossMonitor]
$ns attach-agent $n1 $rcvr1

$ns at 0.5 "$n0 join-group $rcvr0 $group0"
$ns at 1.0 "$n1 join-group $rcvr1 $group0"

$ns at 2.0 "finish"

proc finish {} {
	global ns
	$ns flush-trace

	puts "running nam..."
	exec nam aj/bst1.nam &
	exit 0
}

$ns run




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