How to Start Logical Topology Projects Using NS2

To create a Logical Topology project in NS2 (Network Simulator 2) has includes the replicate of virtual or logical links among the nodes, independent for the physical links. Logical topologies are used to signify overlays or detailed for data flows in a network, like as in software-defined networks (SDNs) or virtual private networks (VPNs).

Here’s how to set up and simulate a Logical Topology project in NS2:

Steps to Start Logical Topology Projects Using NS2

  1. Understand Logical Topology
  • Logical Topology:
    • Characterize on how the data flows among nodes that can change from the physical connections.
    • Sample has involves the star, ring, tree, or mesh logical overlays.
  • Applications:
    • Overlay networks.
    • Virtual LANs (VLANs).
    • Software-Defined Networking (SDN).
  • Advantages:
    • The resource allocation and flexibility in routing.
    • The large networks for consider the scalability.
  1. Set Up NS2
  1. Install NS2:
    • Install and Validate NS2 functionality using a basic script:

ns example.tcl

  1. Tools for Analysis:
    • NAM (Network Animator) intended for topology envision tool.
    • Trace Analysis Tools designed for performance metrics such as throughput and delay.
  1. Plan the Logical Topology
  • Example Logical Topologies:
    • Ring Overlay: Nodes are transmission in a logical ring while being physically linked in a mesh.
    • Star Overlay: Complete data flows through a logical central node.
    • Tree Overlay: Independent of physical connections are flow of data in hierarchical.
  • Metrics to Analyze:
    • The path is logical in latency.
    • The path analyses the simulation results such as Network throughput and packet delivery ratio (PDR).
  1. Write the Simulation Script

Step 4.1: Create the TCL Script

Store the script as logical_topology.tcl.

Step 4.2: Initialize the Simulator

It begin with initializing the replicator and assure the monitoring:

set ns [new Simulator]

set tracefile [open trace.tr w]

$ns trace-all $tracefile

set namfile [open logical_topology.nam w]

$ns namtrace-all $namfile

Step 4.3: Create Nodes

Describe the nodes in a network:

# Create nodes

set n1 [$ns node]

set n2 [$ns node]

set n3 [$ns node]

set n4 [$ns node]

set n5 [$ns node]

Step 4.4: Configure Physical Links

It link the nodes are physically in a full mesh topology:

# Physical Links (Full Mesh)

$ns duplex-link $n1 $n2 1Mb 10ms DropTail

$ns duplex-link $n1 $n3 1Mb 10ms DropTail

$ns duplex-link $n1 $n4 1Mb 10ms DropTail

$ns duplex-link $n1 $n5 1Mb 10ms DropTail

$ns duplex-link $n2 $n3 1Mb 10ms DropTail

$ns duplex-link $n2 $n4 1Mb 10ms DropTail

$ns duplex-link $n2 $n5 1Mb 10ms DropTail

$ns duplex-link $n3 $n4 1Mb 10ms DropTail

$ns duplex-link $n3 $n5 1Mb 10ms DropTail

$ns duplex-link $n4 $n5 1Mb 10ms DropTail

Step 4.5: Define Logical Links

It replicates the logical link through routing congestion with detailed paths:

# Logical Overlay (Ring Topology)

# Traffic from n1 to n2

set udp1 [new Agent/UDP]

$ns attach-agent $n1 $udp1

set null1 [new Agent/Null]

$ns attach-agent $n2 $null1

$ns connect $udp1 $null1

set cbr1 [new Application/Traffic/CBR]

$cbr1 attach-agent $udp1

$cbr1 set packetSize_ 512

$cbr1 set rate_ 100kb

$ns at 1.0 “$cbr1 start”

# Traffic from n2 to n3

set udp2 [new Agent/UDP]

$ns attach-agent $n2 $udp2

set null2 [new Agent/Null]

$ns attach-agent $n3 $null2

$ns connect $udp2 $null2

set cbr2 [new Application/Traffic/CBR]

$cbr2 attach-agent $udp2

$cbr2 set packetSize_ 512

$cbr2 set rate_ 100kb

$ns at 2.0 “$cbr2 start”

# Traffic from n3 to n1 (closing the ring)

set udp3 [new Agent/UDP]

$ns attach-agent $n3 $udp3

set null3 [new Agent/Null]

$ns attach-agent $n1 $null3

$ns connect $udp3 $null3

set cbr3 [new Application/Traffic/CBR]

$cbr3 attach-agent $udp3

$cbr3 set packetSize_ 512

$cbr3 set rate_ 100kb

$ns at 3.0 “$cbr3 start”

Step 4.6: Add Routing Protocol

Use dynamic routing protocols and handle the logical connections:

$ns rtproto DV

Step 4.7: Finalize the Script

Increase the replication end conditions:

$ns at 10.0 “finish”

proc finish {} {

global ns tracefile namfile

$ns flush-trace

close $tracefile

close $namfile

exec nam logical_topology.nam &

exit 0

}

$ns run

  1. Run the Simulation
  1. store the script as logical_topology.tcl.
  2. Process for the replication script:

ns logical_topology.tcl

  1. Start the NAM file for envision the topology:

nam logical_topology.nam

  1. Analyze Results
  • Trace File Analysis:
    • Use trace.tr for examine the throughput, latency, and PDR.
    • Sample AWK script for throughput:

awk ‘{if ($1 == “r” && $4 == “udp”) sum += $8} END {print “Throughput: “, sum}’

  • Metrics:
    • Logical Path Latency: calculate the delays along the logical paths.
    • Throughput: Estimate the effectiveness of the logical topology.
    • Packet Delivery Ratio (PDR): Measure the reliability.
  1. Expand the Simulation
  1. Change Logical Topologies:
    • Research by star, tree, or other overlays.
  2. Simulate Node Failures:
    • Establish the node failures for validate the fault tolerance:

$ns at 5.0 “$ns link-fail $n2 $n3”

  1. Add Multicast Traffic:
    • Setting the multicast congestion for logical groups.
  2. Increase Network Size:
    • Through increasing the further nodes and logical connections for the network scale.
  1. Document the Project
  • Objective: Define the purpose for replicate the logical topology.
  • Setup: It contains the specific nodes, physical connection and logical overlays.
  • Results: Present metrics and visualizations.
  • Conclusions: Sum up the clarifications and improve the potential future.

We clearly accumulated the essential details to Logical topology project with example coding that simulated and evaluated using the tool of ns2 analysis tool. If you have concerns or queries, they will be addressed in a separate manual.