Mutlicast routing in ns2 can be easily set using any
of the following syntax
Method 1:
set ns [new Simulator -multicast on]
Method 2:
set ns
[new Simulator]
$ns multicast
when multicast mode is enabled, the nodes behave differently
with the additional classifiers are created. A distribution tree kind of
structure is created in the simulation when dealing with multicast
routing. NS supports three types of
multicast routing: Centralized Multicast Routing(CM), Dense Mode (DM), Shared
Tree Mode (ST) and Bi directional Shared Tree Support (BST).
Here is the method to specify the multicast routing
in ns.
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set cmc [$ns mrtproto CtrMcast] # specify centralized multicast for all
nodes;
# cmc is the handle for multicast protocol object;
$ns mrtproto DM # specify dense mode
multicast for all nodes;
$ns mrtproto ST # specify shared tree mode
to run on all nodes;
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The agents in the protocol can be joining the group or
leaving the group for multicasting. Two procedures are used join-group[] and
leave-group[].
An example of a relatively simple multicast configuration is:
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set ns [new Simulator -multicast on]; # enable
multicast routing;
set group [Node allocaddr] ; # allocate a multicast address;
set node0 [$ns node] ;# create multicast capable nodes;
set node1 [$ns node]
$ns duplex-link $node0 $node1 1.5Mb 10ms DropTail
set tracef [open dm.tr w]
$ns trace-all $tracef
set namtracef [open dm.nam w]
$ns namtrace-all $namtracef
set mproto DM ; # configure multicast protocol;
set mrthandle [$ns mrtproto $mproto]; # all nodes
will contain multicast protocol agents;
set udp [new Agent/UDP] ;# create a source agent at node 0;
$ns attach-agent $node0 $udp
set cbr [new Application/Traffic/CBR]
$cbr attach-agent $udp
$udp set dst_addr_ $group
$udp set dst_port_ 0
set receiver [new Agent/LossMonitor]; # create a receiver agent at node 1;
$ns attach-agent $node1 $receiver
$ns at 0.3 "$node1 join-group $receiver
$group"
$ns at 0.1 "$cbr start"
$ns at 5.0 "finish"
proc finish {} {
global
ns tracef namtracef
exec
nam dm.nam &
close
$tracef
close
$namtracef
exit 0
}
$ns run
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Sample Output :
The status bar shows that the node1 joins the group
There was no
packet exchange which is discussed in the next topic
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Centralized
Multicast routing in ns2
#This example is to demonstrate the
multicast routing protocol.
set ns [new Simulator -multicast on]
#Turn on Tracing
set tf [open output.tr w]
$ns trace-all $tf
# Turn on nam Tracing
set fd [open mcast.nam w]
$ns namtrace-all $fd
# Create nodes
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]
set n4 [$ns node]
set n5 [$ns node]
set n6 [$ns node]
set n7 [$ns node]
# Create links with DropTail Queues
$ns duplex-link $n0 $n2 1.5Mb 10ms
DropTail
$ns duplex-link $n1 $n2 1.5Mb 10ms
DropTail
$ns duplex-link $n2 $n3 1.5Mb 10ms
DropTail
$ns duplex-link $n3 $n4 1.5Mb 10ms
DropTail
$ns duplex-link $n3 $n7 1.5Mb 10ms
DropTail
$ns duplex-link $n4 $n5 1.5Mb 10ms
DropTail
$ns duplex-link $n4 $n6 1.5Mb 10ms
DropTail
# Routing protocol: say distance
vector
#Protocols: CtrMcast, DM, ST, BST
#Dense Mode protocol is supported in
this example
set mproto DM
set mrthandle [$ns mrtproto $mproto
{}]
# Set two groups with group addresses
set group1 [Node allocaddr]
set group2 [Node allocaddr]
# UDP Transport agent for the traffic
source for group1
set udp0 [new Agent/UDP]
$ns attach-agent $n0 $udp0
$udp0 set dst_addr_ $group1
$udp0 set dst_port_ 0
set cbr1 [new
Application/Traffic/CBR]
$cbr1 attach-agent $udp0
# Transport agent for the traffic
source for group2
set udp1 [new Agent/UDP]
$ns attach-agent $n1 $udp1
$udp1 set dst_addr_ $group2
$udp1 set dst_port_ 0
set cbr2 [new
Application/Traffic/CBR]
$cbr2 attach-agent $udp1
# Create receiver to accept the
packets
set rcvr1 [new Agent/Null]
$ns attach-agent $n5 $rcvr1
$ns at 1.0 "$n5 join-group
$rcvr1 $group1"
set rcvr2 [new Agent/Null]
$ns attach-agent $n6 $rcvr2
$ns at 1.5 "$n6 join-group
$rcvr2 $group1"
set rcvr3 [new Agent/Null]
$ns attach-agent $n7 $rcvr3
$ns at 2.0 "$n7 join-group
$rcvr3 $group1"
set rcvr4 [new Agent/Null]
$ns attach-agent $n5 $rcvr1
$ns at 2.5 "$n5 join-group
$rcvr4 $group2"
set rcvr5 [new Agent/Null]
$ns attach-agent $n6 $rcvr2
$ns at 3.0 "$n6 join-group
$rcvr5 $group2"
set rcvr6 [new Agent/Null]
$ns attach-agent $n7 $rcvr3
#The nodes are leaving the group at
specified times
$ns at 3.5 "$n7 join-group
$rcvr6 $group2"
$ns at 4.0 "$n5 leave-group
$rcvr1 $group1"
$ns at 4.5 "$n6 leave-group
$rcvr2 $group1"
$ns at 5.0 "$n7 leave-group
$rcvr3 $group1"
$ns at 5.5 "$n5 leave-group
$rcvr4 $group2"
$ns at 6.0 "$n6 leave-group
$rcvr5 $group2"
$ns at 6.5 "$n7 leave-group
$rcvr6 $group2"
# Schedule events
$ns at 0.5 "$cbr1 start"
$ns at 9.5 "$cbr1 stop"
$ns at 0.5 "$cbr2 start"
$ns at 9.5 "$cbr2 stop"
#post-processing
$ns at 10.0 "finish"
proc finish {} {
global ns tf
$ns flush-trace
close $tf
exec nam mcast.nam &
exit 0
}
$ns set-animation-rate 3.0ms
$ns run
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Sample Output Screenshots
The
nodes are joining the group before the packet transfer and leaving the group
at a specified time.
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