How to Start Token Ring Topology Projects Using NS2

To start a Token Ring Topology project in NS2 (Network Simulator 2) that has designing a network in which nodes are linked properly within a logical ring and data transmission exists to utilise a token-passing approach. Token Ring networks confirm that proper interaction by allowing transmission rights to nodes within token control.

Below is a basic outline to start and replicate the Token Ring Topology project in NS2:

Steps to Start Token Ring Topology Projects in NS2

  1. Understand Token Ring Topology
  • Token Ring Topology:
    • Nodes are associated within a logical ring.
    • A “token” spreads around the ring by allowing transmission rights to the node that are retaining it.
    • Only the node including the token can be sent the information.
  • Applications:
    • Legacy LAN systems.
    • Industrial control networks.
  • Advantages:
    • Deterministic access to the medium.
    • Collision-free communication.
  1. Set Up NS2
  1. Install NS2:
    • We can set up and confirm NS2 including a simple script:

ns example.tcl

  1. Tools for Analysis:
    • NAM (Network Animator) is designed for visualization.
    • Trace Analysis Tools supports to examine the performance parameters such as throughput and delay.
  1. Plan the Token Ring Topology
  • Topology Structure:
    • Nodes are logically linked within a ring.
    • Data successively flows from one node to the next node.
  • Token Management:
    • A single token is spread between the nodes.
    • Execute token-passing logic for handling transmission.
  1. Write the Simulation Script

Step 4.1: Create the TCL Script

We need to store the tcl simulation script as token_ring_topology.tcl using NS2.

Step 4.2: Initialize the Simulator

Configure the simulator and tracing the file:

# Initialize the simulator

set ns [new Simulator]

set tracefile [open trace.tr w]

$ns trace-all $tracefile

set namfile [open token_ring_topology.nam w]

$ns namtrace-all $namfile

Step 4.3: Create Nodes

We can make nodes in the ring:

# 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 Links

Associate nodes for building a logical ring:

# Logical ring links

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

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

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

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

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

Step 4.5: Implement Token Passing

  • Mimic token passing with the support of a centralized scheduler or custom logic:

# Token passing function

proc pass_token {current next time} {

global ns

$ns at $time “send_token $current $next”

}

# Define token transmission logic

proc send_token {src dst} {

puts “Token passed from $src to $dst at [clock format [clock seconds]]”

# Add logic to enable the token-holder to transmit data

}

Step 4.6: Configure Traffic

Configure traffic flows among the nodes which are managed by token possession:

# Traffic from n1 to n3

set udp1 [new Agent/UDP]

$ns attach-agent $n1 $udp1

set null1 [new Agent/Null]

$ns attach-agent $n3 $null1

$ns connect $udp1 $null1

set cbr1 [new Application/Traffic/CBR]

$cbr1 attach-agent $udp1

$cbr1 set packetSize_ 512

$cbr1 set rate_ 100kb

Step 4.7: Start the Simulation

Now, we can begin the token passing and data transmission:

# Initialize token passing

$ns at 1.0 “pass_token n1 n2 2.0”

$ns at 3.0 “pass_token n2 n3 4.0”

$ns at 5.0 “pass_token n3 n4 6.0”

$ns at 7.0 “pass_token n4 n5 8.0”

$ns at 9.0 “pass_token n5 n1 10.0”

# Start CBR traffic after the token is passed

$ns at 2.5 “$cbr1 start”

Step 4.8: Finalize the Script

Integrate the simulation end and visualization configuration to finish the script:

# End simulation

$ns at 20.0 “finish”

proc finish {} {

global ns tracefile namfile

$ns flush-trace

close $tracefile

close $namfile

exec nam token_ring_topology.nam &

exit 0

}

$ns run

  1. Run the Simulation
  1. We will want to store the script like token_ring_topology.tcl.
  2. Then, run the simulation with NS2:

ns token_ring_topology.tcl

  1. Go to NAM for envisioning the ring topology:

nam token_ring_topology.nam

  1. Analyze Results
  • Trace File Analysis:
    • Examine the performance parameters such as throughput, latency, and token-passing efficiency with the help of trace.tr.
    • Example AWK script for estimating throughput:

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

  • Metrics:
    • Token Passing Latency: Compute the duration to distribute the token.
    • Throughput: Measure the effectiveness of data transfer.
    • Packet Delivery Ratio (PDR): Evaluate reliability for packet delivery rate.
  1. Expand the Simulation
  1. Test Token Loss:
    • Replicate the token loss or duplication and also execute recovery approaches.
  2. Vary Traffic Patterns:
    • Integrate additional traffic flows and then examine its influence over the performance.
  3. Implement Priority-Based Token Passing:
    • Fine-tune the token-passing logic to give precedence for specify nodes.
  4. Add Fault Tolerance:
    • Launch redundant connections, managing the failures.
  1. Document the Project
  • Objective: Define the project’s goals of replicating a token ring topology.
  • Setup: Specify nodes, links, and traffic sets up.
  • Results: It offers performance parameters such as throughput, latency, and token efficiency.
  • Conclusions: Sum up outcomes and recommend enhancements.

This approach ensures a well-structured Token Ring Topology project in NS2 environment. You can start with the basic setup and iteratively add features based on your project’s requirements. For further clarification regarding this topic, please check the additional guide to be offered.