How to Implement OSPF Routing in NS2

To implement the OSPF (Open Shortest Path First) routing within NS2 has needs to contain using existing aspects or extensions, which support the simulation OSPF. Because the NS2 does not natively support the routing OSPF and we can either patch NS2 with an OSPF extension or mimic a custom OSPF-like routing performance by altering the existing NS2 scripts. The following is a simple guidance how to simulate OSPF routing in NS2:

Steps to Implement OSPF in NS2:

  1. Install and Set Up NS2

Make sure NS2 is installed and appropriately configured. We can download NS2 from the official webpage.

  1. Add OSPF Extensions

Because OSPF routing may not be supported natively in NS2 so we will want to install an extension or patch that mimics OSPF performance.

We can be discovered some OSPF simulation patches by finding for “NS2 OSPF patch” or same tools. This patches are append the OSPF protocol support to NS2.

  • Install the OSPF Patch: We download the OSPF patch from a suitable source, then apply it to NS2, and recompile NS2 to permit OSPF support.

To recompile NS2:

cd ns-allinone-2.x/ns-2.x

./configure

make clean

make

  1. Modify Tcl Script to Include OSPF

In the Tcl simulation script, we will require to describe the nodes, network topology, and allowing the OSPF routing.

We provide some instance of a basic Tcl script for OSPF routing:

Example of Tcl Script Using OSPF:

# Create a new simulator instance

set ns [new Simulator]

# Define the network nodes (e.g., routers)

set n0 [$ns node]

set n1 [$ns node]

set n2 [$ns node]

set n3 [$ns node]

# Create duplex links between the nodes

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

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

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

$ns duplex-link $n0 $n3 10Mb 10ms DropTail

# Enable OSPF on the nodes

$n0 enable-OSPF

$n1 enable-OSPF

$n2 enable-OSPF

$n3 enable-OSPF

# Optionally define routing weights or metrics for OSPF (optional)

$n0 set-OSPF-weight $n1 10

$n1 set-OSPF-weight $n2 15

$n2 set-OSPF-weight $n3 5

$n3 set-OSPF-weight $n0 20

# Define the traffic flow between nodes using UDP/CBR traffic

set udp0 [new Agent/UDP]

set udp1 [new Agent/UDP]

$ns attach-agent $n0 $udp0

$ns attach-agent $n3 $udp1

set cbr [new Application/Traffic/CBR]

$cbr attach-agent $udp0

$cbr set packetSize_ 512

$cbr set interval_ 0.1

$cbr set random_ false

$ns connect $udp0 $udp1

# Start the traffic flow

$ns at 1.0 “$cbr start”

# Finish the simulation after 10 seconds

$ns at 10.0 “finish”

$ns run

  1. OSPF Behavior in the Script

In the script:

  • Nodes are made denoting routers that will use OSPF.
  • Duplex links are ascertained among the nodes including bandwidth and latency metrics.
  • OSPF is permitted using a hypothetical $node enable-OSPF function (we will want the OSPF patch for this to work).
  • OSPF weights/metrics can be set among the nodes (optional) to describe the cost for every link, impacting the OSPF’s shortest-path calculation.
  1. Running the Simulation

When the script is prepared, we can run the simulation with the below command in the terminal:

ns ospf_simulation.tcl

It will perform the simulation and displaying how OSPF ascertains the best paths among the nodes rely on the shortest path algorithm.

  1. Analyse the Results

After the simulation runs, NS2 produces trace files, which we can evaluate it then we can visualize the simulation using NAM (Network Animator) to monitor how traffic is routed among the nodes.

  1. Test OSPF Network Failures

We can mimic link failures and monitor how OSPF adjusts by recalculating routes. For sample, we can disable a link midway via the simulation:

# Disable a link at 5 seconds (simulate network failure)

$ns at 5.0 “$ns detach-agent $n1 $n2”

It will mimic a network failure among the nodes n1 and n2, and OSPF will require to recompute the routing paths to prevent the failed link.

  1. Post-Simulation Analysis

We can use the trace files or NAM visualization to check the OSPF’s routing performance. Primary features are contain:

  • Path convergence: How rapidly the OSPF meets on new paths after modifying in network topology.
  • Shortest path: Whether the shortest paths are being selected based on the OSPF cost parameters.

Extensions:

  • Custom OSPF Metrics: We can alter or append various cost metrics for OSPF links, rely on the behaviour and bandwidth necessities.
  • LSA Simulation: OSPF’s Link State Advertisement (LSA) messages can be replicated by appending the custom events in the Tcl script to better simulate the OSPF behaviour.

Above is a demonstration of how to execute and simulate the OSPF routing in the NS2 using the basic approach. More specific details will be shared relevant to this topic as per your needs. Get tailored assistance on OSPF Routing in NS2 implementation. We share with you network analysis  details for your projects drop us all your project details for more guidance.