To simulate Least Cost Routing within NS2 that encompasses configuring a network in which the routing protocol selects the path with the lowest cumulative cost, like bandwidth, delay, or other parameters. Least Cost Routing is usually relying on the algorithms such as Dijkstra’s or Bellman-Ford, which target to reduce the total cost among a source and a destination.
In NS2, we can replicate least cost routing by setting up the network with cost metrics like link delay or bandwidth and utilizing routing protocols, which take those into account. Here’s how we can simulate a Least Cost Routing project using NS2:
Steps to Simulate Least Cost Routing in NS2
- Install NS2
Make sure that NS2 is installed on the computer. If not then we download it from the NS2 Official Website and follow the installation instructions for the operating system.
- Create a TCL Script for Least Cost Routing
In this example, we will configure a network topology with several paths among the nodes and allocate diverse costs (delays) to each link. The routing protocol will automatically select the path with the least cumulative cost (shortest path in terms of delay).
Example TCL Script for Least Cost Routing Simulation:
# Create a simulator object
set ns [new Simulator]
# Define trace and nam files for analysis and visualization
set tracefile [open “least_cost_trace.tr” w]
set namfile [open “least_cost_simulation.nam” w]
$ns trace-all $tracefile
$ns namtrace-all $namfile
# Create network nodes
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]
set n4 [$ns node]
# Define links with different delays (costs)
$ns duplex-link $n0 $n1 1Mb 10ms DropTail # Cost 10ms
$ns duplex-link $n1 $n2 1Mb 20ms DropTail # Cost 20ms
$ns duplex-link $n2 $n3 1Mb 30ms DropTail # Cost 30ms
$ns duplex-link $n3 $n4 1Mb 10ms DropTail # Cost 10ms
$ns duplex-link $n0 $n2 1Mb 15ms DropTail # Cost 15ms (shorter cost than n0->n1->n2)
$ns duplex-link $n1 $n3 1Mb 25ms DropTail # Cost 25ms
# Use routing protocol (NS2 by default uses least cost path based on link delay)
for {set i 0} {$i < 5} {incr i} {
$ns at 0.0 “$n$i start-dv-routing”
}
# Create UDP agent and attach it to node 0 (source)
set udp0 [new Agent/UDP]
$ns attach-agent $n0 $udp0
# Create a traffic generator (CBR) for the UDP agent
set cbr0 [new Application/Traffic/CBR]
$cbr0 set packetSize_ 512
$cbr0 set rate_ 1Mb
$cbr0 attach-agent $udp0
# Attach a UDP sink to destination node (n4)
set udp1 [new Agent/UDP]
$ns attach-agent $n4 $udp1
# Connect the source and destination
$ns connect $udp0 $udp1
# Schedule traffic flow
$ns at 1.0 “$cbr0 start”
$ns at 4.5 “$cbr0 stop”
# Define the finish procedure
proc finish {} {
global ns tracefile namfile
$ns flush-trace
close $tracefile
close $namfile
exit 0
}
# End the simulation at 5 seconds
$ns at 5.0 “finish”
# Run the simulation
$ns run
- Run the Simulation
We can save the script as least_cost_simulation.tcl and execute it in NS2 with the following command:
ns least_cost_simulation.tcl
- Visualize the Simulation with NAM
We can open the generated NAM file to envision the network and observe the routing decisions created according to the least cost:
nam least_cost_simulation.nam
- Analyse the Trace File
The trace file (least_cost_trace.tr) includes data regarding the packet transmissions and the paths selected by the routing protocol. We can investigate this file to check:
- Which path was chosen based on the least cost.
- Packet delivery times.
- End-to-end delay.
- Modifying the Topology
- Cost Variation: We can change the delays on links to signify diverse costs (e.g., bandwidth, packet loss) and monitor how the routing protocol adjusts.
- Link Failures: We can replicate link failures by disabling particular links and verifying how the routing algorithm recalculates the least cost path.
- Scalability: Insert more nodes and links to learn how the least cost routing algorithm scales with larger topologies.
Optional Enhancements:
- Cost Based on Bandwidth: Alter the simulation to get bandwidth or queue length into account for finding out the least cost route.
- Energy-Aware Routing: Replicate routing with energy cost parameters to learn how least cost routing could be applied to wireless sensor networks (WSNs) with energy constraints.
These projects concentrated on how to simulate the Least Cost Routing projects with the help of provided simulation steps with sample snippets using NS2 tool. We are available to deliver more detailed analysis and necessary insights according to your requirements.
To receive assistance with your Least Cost Routing project, simply provide us with the relevant details, and we will connect you with leading experts for simulation support.
