How to Start Least Cost Routing Projects Using NS2

To create a Least Cost Routing project using NS2, follow these steps. Least cost routing goals to measure the optimal path among nodes in a network according to parameter metrics such as latency, bandwidth, or other costs associated with links.

Steps to Start Least Cost Routing Projects Using NS2

Step 1: Set Up NS2 Environment

  1. Install NS2:
    • Download NS2 from the NS2 Official Website.
    • Install essential needs such as Tcl, OTcl, and NAM.
    • Validate the installation with:

ns -version

  1. Understand NS2 Basics:
    • Explain yourself through NS2 scripting such as creating nodes, links, and defining traffic.
    • Analysis for the sample in ns-allinone-2.x/examples/.

Step 2: Understand Least Cost Routing

  1. Overview of Least Cost Routing:
    • It measures the path through the minimum cost among source and destination.
    • Cost parameter metrics can be link delay, bandwidth, hop count, or any custom-defined metric.
  2. Approach:
    • Used the procedure such as Dijkstra’s or Bellman-Ford we calculate the least-cost paths.
    • Update the routing table dynamically as network conditions change.

Step 3: Design Network Topology

  1. State the nodes and connection in the network:

set ns [new Simulator]

 

# Define nodes

set n1 [$ns node]

set n2 [$ns node]

set n3 [$ns node]

set n4 [$ns node]

# Define links with bandwidth, delay, and queue type

$ns duplex-link $n1 $n2 10Mb 5ms DropTail

$ns duplex-link $n1 $n3 5Mb 10ms DropTail

$ns duplex-link $n2 $n4 15Mb 2ms DropTail

$ns duplex-link $n3 $n4 20Mb 1ms DropTail

  1. Allocate the connection costs dynamically according to the bandwidth or delay.

Step 4: Implement Least Cost Routing

Option 1: Tcl Script Implementation

  1. Describe a method to estimate the least-cost paths:

proc leastCostRouting {nodes links src} {

set costs {}

set nextHop {}

# Initialize costs and next hops

foreach node $nodes {

if {$node == $src} {

set costs($node) 0

} else {

set costs($node) inf

}

set nextHop($node) -1

}

# Dijkstra’s algorithm for least cost routing

set visited {}

while {[llength $visited] < [llength $nodes]} {

set currentNode {}

set minCost inf

# Find the unvisited node with the lowest cost

foreach node $nodes {

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

set currentNode $node

set minCost $costs($node)

}

}

# Mark the current node as visited

set visited($currentNode) 1

# Update costs for neighbors

foreach {from to cost} $links {

if {$from == $currentNode && ![info exists visited($to)]} {

if {$costs($currentNode) + $cost < $costs($to)} {

set costs($to) [expr $costs($currentNode) + $cost]

set nextHop($to) $currentNode

}

}

}

}

# Print routing table

foreach node $nodes {

puts “Node $node: Cost = $costs($node), Next Hop = $nextHop($node)”

}

}

  1. Call the methods for the network’s nodes and links:

set nodes {n1 n2 n3 n4}

set links {n1 n2 5 n1 n3 10 n2 n4 2 n3 n4 1}

leastCostRouting $nodes $links n1

Option 2: C++ Implementation in NS2

  1. Build a new routing agent:
    • Spread the Agent class we maintain the least-cost routing.

Example:

class LeastCostAgent : public Agent {

public:

LeastCostAgent();

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

void calculateLeastCostPaths();

private:

std::map<int, int> costTable; // Node -> Cost

std::map<int, int> nextHopTable; // Node -> Next Hop

};

  1. Apply the Dijkstra’s procedure in calculateLeastCostPaths.
  2. Compile the new agent:
    • Alter the NS2 Makefile has involves modify the agent.
    • Recompile NS2:

make clean && make

Step 5: Define Traffic Flow

  1. Enhance the congestion sources and sinks:

# Attach agents

set udp [new Agent/UDP]

$ns attach-agent $n1 $udp

set sink [new Agent/Null]

$ns attach-agent $n4 $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. Follow on how the packets are routed according to the least-cost routing methods.

Step 6: Simulate and Analyze

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

ns least_cost_routing.tcl

  1. Envision the outcomes using NAM:

nam least_cost_routing.nam

  1. Examine the trace file for:
    • Path selection based on cost.
    • Packet delivery ratio.
    • Latency metrics.

Step 7: Enhance the Project

  1. Dynamic Costs:
    • Bring up-to-date connection costs according to the congestion load or network environments.
    • Modify the replication for link state for sample failures or congestion.
  2. Performance Metrics:
    • Calculate the throughput, end-to-end delay, and energy efficiency such as if in WSNs.
  3. Comparison:
    • Associate the least-cost routing through other routing protocols such as OSPF or AODV.
  4. Scalability Testing:
    • Validate the procedures on the larger topologies through 20+ nodes.

In the entire page will talk about how effectively Least Cost routing will perform in the tool of ns2 simulation tool and also we provide the sample snippets, example overview and the future consideration for deploying the Least Cost routing. Another manual will cover any additional questions about this project.