How to Start Irregular Topology Projects Using NS2

To create an Irregular Topology in NS2 (Network Simulator 2) has custom a model for network architecture in which the nodes are linked in non-uniform or non-standard designs. These topologies are generally used in the real-world networks in which the restriction such as geography, resource availability, or application-specific requirements dictates irregular connections. Here’s how to start your Irregular Topology project in NS2:

Steps to Simulate Irregular Topology in NS2

  1. Understand Irregular Topology
  • Structure:
    • The nodes are linked in the random, non-uniform way.
    • There is no predefined design such as mesh, ring, or star.
  • Applications:
    • Wireless sensor networks (WSNs) by irregular deployment.
    • Geographically constrained areas in networks.
    • Custom the transmission networks for detailed applications.
  1. Set Up NS2
  1. Install NS2:

sudo apt-get install ns2

  1. Verify Installation: Validate by a basic replication of  script:

ns example.tcl

  1. Define Irregular Topology
  • The replication areas are placed in the nodes randomly.
  • Describe the connections are manually according to application-specific requirements.
  1. TCL Script for Irregular Topology

Under the sample the TCL script for replicating the Irregular Topology:

TCL Script Example

# Initialize NS2 Simulator

set ns [new Simulator]

set tracefile [open irregular_topology.tr w]

$ns trace-all $tracefile

# Define number of nodes

set num_nodes 6

# Create nodes

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

set n($i) [$ns node]

}

# Define irregular connections

# Example: Node 0 connects to Node 1 and Node 2

$ns duplex-link $n(0) $n(1) 1Mb 10ms DropTail

$ns duplex-link $n(0) $n(2) 512Kb 15ms DropTail

# Example: Node 1 connects to Node 3

$ns duplex-link $n(1) $n(3) 1Mb 5ms DropTail

# Example: Node 2 connects to Node 4

$ns duplex-link $n(2) $n(4) 2Mb 20ms DropTail

# Example: Node 3 connects to Node 5

$ns duplex-link $n(3) $n(5) 1Gb 1ms DropTail

# Attach agents for traffic simulation

# Traffic from Node 0 to Node 5

set tcp0 [new Agent/TCP]

$ns attach-agent $n(0) $tcp0

set sink0 [new Agent/TCPSink]

$ns attach-agent $n(5) $sink0

$ns connect $tcp0 $sink0

# Add a traffic generator

set ftp [new Application/FTP]

$ftp attach-agent $tcp0

# Start traffic

$ns at 1.0 “$ftp start”

# End simulation

$ns at 5.0 “finish”

proc finish {} {

global ns tracefile

$ns flush-trace

close $tracefile

exit 0

}

$ns run

  1. Key Features to Simulate
  1. Custom Traffic Patterns:
    • It replicates the communication among the nodes by irregular connectivity.
  2. Performance Metrics:
    • Throughput: Calculate the data delivery among detailed nodes.
    • Latency: Examine the delays for caused through irregular paths for latency.
    • Congestion: Estimate the network bottlenecks for non-uniform connections.
  1. Analyze Trace File
  • Use the trace file such as irregular_topology.tr for examines the network performance.
  • Excerpt the detailed metrics:
    • Throughput:

grep “tcp” irregular_topology.tr > throughput.log

    • Dropped Packets:

grep “drop” irregular_topology.tr > dropped_packets.log

  1. Visualize Results

Use the tool Gnuplot or another envision tool:

  1. Throughput Graph:

set title “Irregular Topology Throughput”

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

  1. Latency Graph:
    • Envision for the delays in congestion among detailed nodes.
  1. Extend the Simulation
  2. Dynamic Topology Changes
  • It replicate the dynamic connection build or eliminate:

$ns at 3.0 “$ns duplex-link $n(4) $n(5) 1Mb 10ms DropTail”

  1. Node or Link Failures
  • validate the network’s for resilience through replicating the node or connection failures:

$ns at 2.5 “$ns reset-links $n(0) $n(1)”

  1. Test Different Traffic Patterns
  • Improve the additional congestion flows:

set udp0 [new Agent/UDP]

$ns attach-agent $n(3) $udp0

set null0 [new Agent/Null]

$ns attach-agent $n(4) $null0

$ns connect $udp0 $null0

  1. Experiment with Protocols
  • Use the change protocols for instance UDP vs TCP for follow the effect of irregular topology:

set udp1 [new Agent/UDP]

$ns attach-agent $n(2) $udp1

set null1 [new Agent/Null]

$ns attach-agent $n(5) $null1

$ns connect $udp1 $null1

  1. Modify NS2 Core for Advanced Features
  1. Custom Routing Logic:
    • Execution for detailed routing protocols in irregular topologies.
  2. Traffic Management:
    • Enhance the mechanisms for prioritize or balance congestion among the nodes.

Tools and Resources

  • Wireshark: Examine the congestion designs in an irregular network.
  • Gnuplot: Envision of the performance of parameter metrics such as throughput and latency.
  • NS2 Documentation: Reference for encompassing the functionality and customizations.

Enhancements

  • It replicate the Wireless Irregular Topologies:
    • Use the wireless connection and place the nodes at arbitrary areas.
  • Add QoS Models:
    • Establish the priority-based congestion for estimate the effect of non-uniform connectivity.
  • Compare Irregular vs Standard Topologies:
    • Examine the performance variances among the irregular and regular topologies for sample star, tree, or mesh.

In the end we provide the information about how to calculate and measure irregular topology in the ns2 simulation tool and further assistance regarding the project will be provided in another manual.