To simulate Multicast Routing using NS2 that includes setting up multicast-enabled routing protocols that permit data to be transmitted from one source to numerous receivers concurrently. The network simulator NS2 supports multiple multicast routing protocols like Protocol Independent Multicast (PIM), Distance Vector Multicast Routing Protocol (DVMRP), and Multicast Extensions to OSPF (MOSPF).
Here’s a step-by-step guidelines to replicating multicast routing projects using NS2.
Steps to Simulate Multicast Routing in NS2
- Set Up NS2 Environment
Make certain that NS2 is properly installed and configure on the machine. We can verify this by executing:
ns
If NS2 is installed appropriately then this will open the NS2 shell.
- Understanding Multicast Routing
Multicast routing permits a single source to send data to several receivers (known as a multicast group). The multicast routing protocols make sure that data is efficiently routed to all receivers that minimizing redundant transmissions.
- Configure Multicast Routing in NS2
Multicast routing can be executed utilizing a various kind of protocols. Following is a simple instance of multicast routing using the Protocol Independent Multicast (PIM) protocol.
- Writing a TCL Script for Multicast Routing
Below is a sample TCL script for configuring a multicast routing simulation using NS2:
# Create a simulator object
set ns [new Simulator]
# Open trace and NAM files
set tracefile [open out.tr w]
set namfile [open out.nam w]
$ns trace-all $tracefile
$ns namtrace-all $namfile
# Define network topology
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]
set n4 [$ns node]
set n5 [$ns node]
# Create links between the nodes
$ns duplex-link $n0 $n1 1Mb 10ms DropTail
$ns duplex-link $n1 $n2 512Kb 20ms DropTail
$ns duplex-link $n1 $n3 1Mb 10ms DropTail
$ns duplex-link $n3 $n4 512Kb 20ms DropTail
$ns duplex-link $n3 $n5 1Mb 10ms DropTail
# Enable multicast routing using PIM protocol
$ns rtproto Session
# Create multicast group
set group [Node allocaddr]
# Create a UDP agent and attach it to the source (n0)
set udp0 [new Agent/UDP]
$ns attach-agent $n0 $udp
# Create a Null agent and attach it to the receivers (n2, n4, n5)
set null2 [new Agent/Null]
set null4 [new Agent/Null]
set null5 [new Agent/Null]
$ns attach-agent $n2 $null2
$ns attach-agent $n4 $null4
$ns attach-agent $n5 $null5
# Connect the source to the multicast group
$ns connect $udp0 $null2
$ns connect $udp0 $null4
$ns connect $udp0 $null5
# Join the multicast group at nodes n2, n4, and n5
$n2 join-group $udp0 $group
$n4 join-group $udp0 $group
$n5 join-group $udp0 $group
# Create a CBR traffic source and attach it to the UDP agent
set cbr [new Application/Traffic/CBR]
$cbr set packetSize_ 512
$cbr set interval_ 0.005
$cbr attach-agent $udp0
# Schedule events
$ns at 1.0 “$cbr start”
$ns at 4.0 “$cbr stop”
$ns at 5.0 “finish”
# Define the finish procedure
proc finish {} {
global ns tracefile namfile
$ns flush-trace
close $tracefile
close $namfile
exec nam out.nam &
exit 0
}
# Run the simulation
$ns run
- Explanation of the Script
- Multicast Group: A multicast group is made using set group [Node allocaddr], and nodes n2, n4, and n5 are inserted to the group utilizing the join-group command.
- Routing Protocol: The command $ns rtproto Session configures PIM (Protocol Independent Multicast) as the multicast routing protocol within NS2. This protocol efficiently handles multicast routing according to the multicast session.
- Traffic: A UDP agent is utilized to transmit Constant Bit Rate (CBR) traffic from node n0 (source) to every nodes in the multicast group (n2, n4, and n5).
- Multicast Delivery: The data packets are distributed from n0 to the multicast group members without duplicating the transmission for each receiver.
- Running the Simulation
To execute the multicast routing simulation, we can save the script as multicast_routing.tcl and run it using:
ns multicast_routing.tcl
It will make a trace file (out.tr) and a NAM file (out.nam) for envisioning the simulation.
- Visualizing the Simulation
We can envision the multicast transmission using NAM:
nam out.nam
The NAM tool will indicate the source node (n0) transmitting packets to numerous receivers (n2, n4, and n5), which following the multicast routing tree constructed by the PIM protocol.
- Customizing the Simulation
We can further modify the multicast routing simulation by:
- Changing the multicast protocol: The network simulator NS2 also supports DVMRP and MOSPF for multicast routing. We can switch protocols by modifying $ns rtproto Session to the respective protocol, if required.
- Increasing the number of multicast receivers: Insert more nodes and have them join the multicast group.
- Testing different traffic types: Utilize TCP traffic or test with distinct CBR traffic rates.
- Simulating Link Failures
We can replicate link failures and monitor how multicast routing adjusts by inserting the link failure commands in the script:
# Simulate a link failure between n1 and n3 at 2.5 seconds
$ns rtmodel-at 2.5 down $n1 $n3
# Restore the link at 4.0 seconds
$ns rtmodel-at 4.0 up $n1 $n3
It will push the multicast routing protocol to recompute the multicast tree once a link goes down, replicating real-world network dynamics.
- Analyzing the Results
The trace file (out.tr) will encompass detailed data regarding packet transmissions, routing decisions, and multicast group memberships. We can utilize the tools such as awk or grep to parse the trace file and accumulate performance parameters such as throughput, delay, and packet loss.
For instance, to calculate the number of packets received:
grep “^r” out.tr | wc -l
- Performance Evaluation
Estimate the performance of multicast routing by examining parameters like:
- Packet Delivery Ratio (PDR): The percentage of multicast packets is delivered to the group members.
- Routing Overhead: The amount of control packets utilized to maintain the multicast routing tree.
- Scalability: Experiment the performance by maximizing the amount of receivers in the multicast group.
Overall, we have entirely instructed through the brief execution and simulation process relevant to the Multicast Routing projects, which is simulated using NS2 simulation environment. If necessary, we will provide the detailed approach of this project for you.
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