How to Start Ring Topology Projects Using NS2

To start simulating a Ring Topology utilising NS2 (Network Simulator 2), we want to make a network in which nodes are allocated in a circular way, and every single node is associated to two other nodes accurately. Interaction normally adheres to a unidirectional or bidirectional flow over the ring.

Below is a sequential method to get started with Ring Topology project in NS2:

Steps to Start Ring Topology in NS2

1. Understand Ring Topology

• Structure:
  • Nodes are linked within a circular set up.
  • Data flows in one or both directions over the ring.
• Applications:
  • This topology is frequently leveraged in metropolitan area networks (MANs) and token-based protocols.

2. Set Up NS2

1. Install NS2:

sudo apt-get install ns2

1. Verify Installation: Confirm installation including a simple example script:

ns example.tcl

3. Define Ring Topology

• Nodes (n0, n1… nN) are associated within a ring.
• Links can be unidirectional or bidirectional.
• Clearly specify the circular connections in the script.

4. TCL Script for Ring Topology

Here’s a sample TCL script for a Ring Topology:

TCL Script Example

# Initialize NS2 Simulator

set ns [new Simulator]

set tracefile [open ring_topology.tr w]

$ns trace-all $tracefile

# Number of nodes in the ring

set num_nodes 5

# Create nodes

for {set i 0} {$i < $num_nodes} {incr i} {

set n($i) [$ns node]

}

# Create links to form a ring

for {set i 0} {$i < $num_nodes} {incr i} {

set next [expr ($i + 1) % $num_nodes]

$ns duplex-link $n($i) $n($next) 1Mb 10ms DropTail

}

# Attach agents to simulate traffic

# Example: n0 sends to n2, n1 sends to n3

set udp0 [new Agent/UDP]

$ns attach-agent $n(0) $udp0

set null0 [new Agent/Null]

$ns attach-agent $n(2) $null0

$ns connect $udp0 $null0

set udp1 [new Agent/UDP]

$ns attach-agent $n(1) $udp1

set null1 [new Agent/Null]

$ns attach-agent $n(3) $null1

$ns connect $udp1 $null1

# Add traffic generators

set cbr0 [new Application/Traffic/CBR]

$cbr0 set packetSize_ 512

$cbr0 set interval_ 0.2

$cbr0 attach-agent $udp0

set cbr1 [new Application/Traffic/CBR]

$cbr1 set packetSize_ 512

$cbr1 set interval_ 0.3

$cbr1 attach-agent $udp1

# Start traffic

$ns at 1.0 “$cbr0 start”

$ns at 1.5 “$cbr1 start”

# End simulation

$ns at 5.0 “finish”

proc finish {} {

global ns tracefile

$ns flush-trace

close $tracefile

exit 0

}

$ns run

5. Key Features to Simulate

• Traffic Flow: Make sure that data properly passes through the ring.
• Performance Metrics: Estimate the performance parameters such as throughput, delay, and packet loss.
• Fault Tolerance: Replicate a node or link failure and then monitor the effect.

6. Analyze the Trace File

• The trace file as ring_topology.tr supports to record all packet events.
• Filter and examine certain parameters like:
  • Throughput:

grep “tcp” ring_topology.tr > throughput.log

• • Dropped Packets:

grep “drop” ring_topology.tr > dropped_packets.log

7. Visualize Results

To envision the outcomes we can utilise Gnuplot or another plotting tool:

1. Throughput over time:

set title “Ring Topology Throughput”

plot “throughput.log” using 1:2 with lines title “Throughput”

1. Delay: Examine packet delay models.

8. Extend the Simulation
9. Simulate Token Passing

• Execute a token-based interaction method.
• Make sure that the node with the token can be transmitted only the information.

1. Fault Tolerance

• Replicate the node or link failures and redirect traffic flows across the ring.

1. Bidirectional Ring

• We can integrate the reverse-direction connections for replicating redundancy.

1. Advanced Traffic

• Integrate additional nodes including diverse traffic models such as multimedia or bulk data.

9. Modify NS2 Core for Advanced Features

For advanced aspects, we can:

1. Token-Based Communication: Fine-tune the recv() mechanism within a custom agent to verify for a token.

void RingNode::recv(Packet* p) {

if (hasToken()) {

processPacket(p);

} else {

forwardToken();

}

}

1. Node Failures: Replicate the node or link failures by losing packets in certain scenarios.

Tools and Resources

• Wireshark: Examine the traffic models within the trace file.
• Gnuplot: Envision the performance indicators such as throughput, delay, and other parameters using Gnuplot tools.
• NS2 Documentation: Suggest NS2 documentation for custom agents and topology extensions.

Enhancements

• Replicate the real-world applications such as metropolitan area networks (MANs).
• Equate the performance of unidirectional vs bidirectional rings.
• Add QoS parameters for examining the performance in multimedia traffic.

Using NS2 platform, we developed a solid simulation approach for replicating and analysing the Ring Topology Projects, with the ability to expand this project further for greater clarity as required.