How to Implement Dijkstra’s Link State Routing in NS2

To implement Dijkstra’s Link State Routing Algorithm in NS2 (Network Simulator 2), we need to tailor the routing logic. NS2 lacks built-in implementation of Dijkstra’s algorithm; however you can replicate it by manually stating the link costs and writing custom TCL or C++ code to apply link-state routing with Dijkstra’s algorithm.

Steps to Implement Dijkstra’s Link State Routing in NS2:

  1. Modify Routing Protocol in NS2

We have to implement the Dijkstra’s algorithm by altering the available source code or generating a custom routing logic because of NS2 uses dynamic routing protocols like AODV, DSDV, and DSR. You’ll need to set up the routing algorithm based on link states using either TCL or by fine-tuning the C++ code in NS2.

  1. Create a TCL Script for Network Simulation

Below is a simplified example of how you can configure a network in NS2 and manually state link costs. You can execute the Dijkstra’s algorithm by manually developed the network topology and determining link costs to replicate the selection of the shortest path.

Example TCL Script for Simulating Dijkstra’s Algorithm:

# Create the simulator object

set ns [new Simulator]

# Open a trace file for writing

set tracefile [open dijkstra_trace.tr w]

$ns trace-all $tracefile

# Open a nam file for network animation

set namfile [open dijkstra_simulation.nam w]

$ns namtrace-all $namfile

# Define the finish procedure

proc finish {} {

global ns tracefile namfile

$ns flush-trace

close $tracefile

close $namfile

exec nam dijkstra_simulation.nam &

exit 0

}

# Create 6 nodes in the network

set n0 [$ns node]

set n1 [$ns node]

set n2 [$ns node]

set n3 [$ns node]

set n4 [$ns node]

set n5 [$ns node]

# Define the links between the nodes with bandwidth, delay, and cost (for Dijkstra)

# These link costs are used to calculate the shortest path

$ns duplex-link $n0 $n1 2Mb 10ms DropTail

$ns duplex-link $n1 $n2 2Mb 5ms DropTail

$ns duplex-link $n2 $n3 2Mb 5ms DropTail

$ns duplex-link $n3 $n4 2Mb 10ms DropTail

$ns duplex-link $n0 $n4 2Mb 20ms DropTail

$ns duplex-link $n4 $n5 2Mb 15ms DropTail

$ns duplex-link $n2 $n5 2Mb 5ms DropTail

# Manually setting link costs to simulate Dijkstra’s shortest path selection

# The shortest path from n0 to n5 is expected to be n0 -> n1 -> n2 -> n5

# because n0 -> n4 -> n5 has higher delay (cost)

# Setup UDP agents and attach them to nodes

set udp0 [new Agent/UDP]

$ns attach-agent $n0 $udp0

set null0 [new Agent/Null]

$ns attach-agent $n5 $null0

# Connect the agents

$ns connect $udp0 $null0

# Setup CBR (Constant Bit Rate) traffic over UDP

set cbr [new Application/Traffic/CBR]

$cbr set packetSize_ 512

$cbr set interval_ 0.2

$cbr attach-agent $udp0

# Define simulation events

$ns at 0.1 “$cbr start”

$ns at 5.0 “$cbr stop”

$ns at 6.0 “finish”

# Run the simulation

$ns run

  1. Explanation of the Script:
  • Nodes and Links: The script states 6 nodes linked with duplex links. The bandwidth, delay, and cost are noted on each link. These delays simulate the “cost” used in Dijkstra’s algorithm.
  • Link Costs: By manually configuring the link delays (e.g., 10ms, 5ms, 20ms), we simulate the link costs. The shortest path should be n0 -> n1 -> n2 -> n5 depends on the lower delay (cost).
  • Traffic Setup: A UDP agent creates traffic amongst node n0 and node n5. Constant Bit Rate (CBR) traffic is deliver over the UDP agent.
  1. Simulating Dijkstra’s Algorithm:

Even though NS2 does not automatically execute Dijkstra’s algorithm, the simulation emulates it by building the network topology and link costs. The shortest path is indirectly selected according to the the lowest link cost (in this case, the lowest delay).

  1. Running the Simulation:

Store the TCL script as dijkstra_example.tcl and execute it using the given command:

ns dijkstra_example.tcl

This will create two output files:

  • dijkstra_trace.tr: The trace file stores the packet movements and network activity.
  • dijkstra_simulation.nam: The NAM file for visualizing the network activity.

Use the below command to visualize the simulation in NAM (Network Animator):

nam dijkstra_simulation.nam

  1. Further Implementation in C++:

If you want to truly execute Dijkstra’s algorithm in the core routing logic of NS2 (in C++), you would need to:

  • Adjust the NS2 source code.
  • Accomplish the Dijkstra’s algorithm in the routing layer (possibly in ~/ns-2.xx/queue/route.cc or another routing module).
  • Compile NS2 with your custom alterations.

At the end of this demonstration, we come up with the step-by-step implementation and basic network setup of the Dijkstra’s link state using simulated Dijkstra algorithm in the ns2 tool. If you have any doubts about this approach, we will clarify it. Connect with ns2project.com today! We’re here to provide you with top-notch implementation of Dijkstra’s Link State Routing in NS2. Additionally, we offer excellent research ideas customized to fit your project needs.