How to Start OSPF Routing Projects Using NS2

To create an OSPF (Open Shortest Path First) routing project using NS2, we will require apply or replicate the behavior of OSPF, as NS2 does not natively include it. Below is a organized method to designing and applying OSPF routing in NS2.

Steps to Start OSPF Routing Projects Using NS2

Step 1: Setup NS2 Environment

  1. Install NS2:
    • Download and install NS2 from the NS2 Official Website.
    • Validate the installation:

ns -version

  1. Explore NS2 Examples:
    • Examine the routing samples in the ns-allinone-2.x/examples/ directory.

Step 2: Understand OSPF

  1. Overview of OSPF:
    • A link-state routing protocol used in IP networks.
    • Routers modify the link-state advertisements (LSAs) we create a network topology.
    • Dijkstra’s algorithm is used we calculate the minimum path tree.
  2. Key Features of OSPF:
    • Hierarchical structure is using the areas.
    • Cost metrics according to the route estimation.
    • Handles for dynamic bring up-to-date and recovery the fault.

Step 3: Design Network Topology

  1. Describe the nodes and connection in your NS2 Tcl script:

set ns [new Simulator]

 

# Create nodes

set r1 [$ns node]

set r2 [$ns node]

set r3 [$ns node]

set r4 [$ns node]

# Define links with bandwidth and delay

$ns duplex-link $r1 $r2 10Mb 10ms DropTail

$ns duplex-link $r2 $r3 5Mb 15ms DropTail

$ns duplex-link $r3 $r4 15Mb 5ms DropTail

$ns duplex-link $r1 $r4 20Mb 20ms DropTail

  1. Setting the several sectors for a hierarchical OSPF network:
    • Group routers into areas (e.g., Area 0, Area 1).

Step 4: Implement OSPF Routing

Since NS2 does not natively has involves the OSPF, you have two options:

Option 1: Simulate OSPF in Tcl

  1. Define Link-State Advertisements (LSAs):
    • Simulate LSA generation and exchange.

proc generateLSA {router neighbors} {

puts “Router $router sending LSAs to neighbors: $neighbors”

foreach neighbor $neighbors {

# Simulate LSA exchange

puts “LSA sent to $neighbor”

}

}

  1. Calculate Shortest Paths:
    • Used the Dijkstra’s algorithm to calculate the minimum path tree.

proc calculateShortestPath {src topology} {

set visited {}

set cost($src) 0

foreach node [array names topology] {

if {$node != $src} {

set cost($node) inf

}

}

while {[llength $visited] < [array size topology]} {

set minCost inf

set currentNode “”

foreach node [array names cost] {

if {![info exists visited($node)] && $cost($node) < $minCost} {

set minCost $cost($node)

set currentNode $node

}

}

set visited($currentNode) 1

# Update costs for neighbors

foreach neighbor [array names topology($currentNode)] {

set newCost [expr $cost($currentNode) + $topology($currentNode,$neighbor)]

if {$newCost < $cost($neighbor)} {

set cost($neighbor) $newCost

}

}

}

return $cost

}

  1. Assign Routes:
    • Setting the routes based on the minimum path tree.

Option 2: Implement OSPF in C++

  1. Extend the Routing Agent Class:
    • Build alter a routing agent for OSPF.
    • Apply the methods for:
      • LSA generation and flooding.
      • It managed the topology databse.
      • Measure the minimum path using Dijkstra’s algorithm.

Example:

class OSPFAgent : public Agent {

public:

OSPFAgent();

void recv(Packet* p, Handler* h);

void generateLSA();

void calculateShortestPath();

private:

std::map<int, std::map<int, int>> topology; // Node -> (Neighbor -> Cost)

};

  1. Compile and Link:
    • Alter the NS2 Makefile has involves the modify OSPF agent.
    • Recompile:

make clean && make

Step 5: Define Traffic Flows

  1. Add traffic sources and sinks:

set udp [new Agent/UDP]

$ns attach-agent $r1 $udp

set sink [new Agent/Null]

$ns attach-agent $r4 $sink

$ns connect $udp $sink

# Generate traffic

set cbr [new Application/Traffic/CBR]

$cbr attach-agent $udp

$cbr set packetSize_ 512

$cbr set interval_ 0.05

$ns at 1.0 “$cbr start”

  1. Replicate the dynamic bring up-to-date through adjusting connection costs or introducing failures.

Step 6: Simulate and Analyze

  1. Store the script as ospf_routing.tcl.
  2. Process for the replication:

ns ospf_routing.tcl

  1. Envision the replication in NAM (Network Animator):

nam ospf_routing.nam

  1. Examine the trace file to verify:
    • LSA exchanges.
    • Shortest path calculations.
    • Packet delivery ratio, latency, and throughput.

Step 7: Enhance the Project

  1. Add Areas and Hierarchy:
    • Split the network into several regions.
    • Replicate the Area Border Routers (ABRs).
  2. Simulate Failures:
    • Establish the connection or node failures and follow on the route recalculations.
  3. Compare with Other Protocols:
    • Estimate the OSPF performance against protocols such as RIP or AODV.
  4. Performance Metrics:
    • Calculate the convergence time, routing overhead, and scalability.

In this given module, we had explicitly focussed the novel information on how to simulate the Open Shortest Path First project that was executed using ns2 tool. If you need more information concerning this process we will explain it based on your needs.