[ns] DM multicast tree is not pruned with LAN

[Toshikazu Ichikawa <ichikawa@toshikazu.org>]

hi, 

  I'm going to simulate the multicast rate control.
I used LAN in my topology, then a trouble happened.
Normaly, multicast tree is pruned when no receiver exist in down stream.
Although, it not work in the topology containing LAN on its leaf.

I set multicast configulation like below:
DM set PruneTimeout 30
set mproto DM
set mrthandle [$ns mrtproto $mproto {}]

Ns manual says DM implementation works on point-to-point links
as well as LANs and adapts to the network dynamics.

I will show simple script for test.
the prune mechanism do not work in this scenario.
Why?

thank, 

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

# prune/graft packets
$ns color 0 blue
$ns color 1 red
$ns color 30 purple
$ns color 31 bisque

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

$ns duplex-link $n0 $n1 1Mbps 10ms DropTail
$ns duplex-link-op $n0 $n1 queuePos 0.5
$ns duplex-link $n1 $n2 1Mbps 10ms DropTail
$ns duplex-link-op $n1 $n2 queuePos 0.5

# with LAN, multicast tree is not pruned
$ns make-lan "$n2 $n3" 1Mbps 10ms LL Queue/DropTail Mac/802_3
# with Link, multicast tree is pruned
#$ns duplex-link $n2 $n3 1Mbps 10ms DropTail
#$ns duplex-link-op $n2 $n3 queuePos 0.5

DM set PruneTimeout 30
set mproto DM
set mrthandle [$ns mrtproto $mproto {}]
set group0 [Node allocaddr]

set udp0 [new Agent/UDP]
$ns attach-agent $n0 $udp0
$udp0 set dst_addr_ $group0
$udp0 set dst_port_ 0
$udp0 set class_ 0
set cbr0 [new Application/Traffic/CBR]
$cbr0 attach-agent $udp0

set rcvr [new Agent/LossMonitor]
$ns attach-agent $n3 $rcvr
$ns at 0.5 "$n3 join-group $rcvr $group0"
$ns at 0.6 "$n3 leave-group $rcvr $group0"

$ns at 0.1 "$cbr0 start"

$ns at 1.0 "finish"

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

        puts "running nam..."
        exec nam out.nam &
        exit 0
}

$ns run


-- 
Toshikazu Ichikawa <ichikawa@toshikazu.org>