How to Start Bellman Ford Routing Projects Using OMNeT++

To start a Bellman-Ford Routing project using OMNeT++, we will need to execute or modify a routing protocol, which utilised the Bellman-Ford algorithm to determine the shortest paths. Bellman-Ford is normally utilised for Distance Vector Routing (DVR) protocols in which every single node calculates the routes according to the data that are obtained from their neighbors. Following is a comprehensive approach to get started:

Steps to Start Bellman-Ford Routing Projects in OMNeT++

  1. Set Up Your Environment

Install OMNeT++

  • We should download and install the OMNeT++ environment on the system.
  • Adhere to the installation guidance and make sure that OMNeT++ is properly working.

Install INET Framework

  • We have to download the INET framework with OMNeT++ version.
  • Construct the framework:

make makefiles

make

INET framework offers a basis for network protocols and simulations.

  1. Understand Bellman-Ford Algorithm
  • Key Features:
    • It helps to determine the shortest path from a source to every other node.
    • Utilises a distance vector table that is iteratively updated with the support of neighbors’ data.
  • Update Rule:
    • Every single node modernizes their routing table to utilise: D(v)=min⁡u∈neighbors{c(u,v)+D(u)}D(v) = \min_{u \in \text{neighbors}} \{c(u, v) + D(u)\}D(v)=u∈neighborsmin​{c(u,v)+D(u)} Where:
      • D(v)D(v)D(v): Current distance to node vvv.
      • c(u,v)c(u, v)c(u,v): Cost of the link among the nodes uuu and vvv.
      • D(u)D(u)D(u): Known distance to uuu.
  1. Plan Your Simulation

Define Network Topology

  • Make a network topology like grid, ring, or random.
  • Define the link weights such as hop count, delay, or bandwidth.

Simulation Objectives

  • Execute the Bellman-Ford algorithm for routing.
  • We have to estimate the performance parameters like:
    • Path optimality.
    • Routing overhead.
    • Convergence time.
  1. Create an OMNeT++ Project
  1. Go to OMNeT++ IDE.
  2. Select File > New > OMNeT++ Project.
  3. Name it to the project as BellmanFordRouting and choose Finish.
  1. Implement Bellman-Ford Routing

Create a Custom Routing Module

  • Prolong the base routing module like inet::RoutingTable or inet::NetworkProtocol.
  • Bellman-Ford Logic:
    • Sustain a distance vector on each node.
    • Propagate the distance vector periodically to neighbors.
    • Modernize the routing table to utilise the received distance vectors.
  • Example Implementation:

class BellmanFordRouting : public cSimpleModule {

private:

std::map<int, double> distanceVector; // Node-to-cost mapping

std::map<int, int> nextHop;          // Node-to-next-hop mapping

protected:

virtual void initialize() override {

// Initialize distance vector

int nodeId = getId();

distanceVector[nodeId] = 0; // Distance to itself is 0

for (int i = 0; i < numNeighbors; i++) {

distanceVector[neighborIds[i]] = INFINITY; // Unknown initially

}

}

virtual void handleMessage(cMessage *msg) override {

// Handle incoming distance vector

auto packet = check_and_cast<DistanceVectorPacket *>(msg);

updateDistanceVector(packet->getVector());

}

void updateDistanceVector(const std::map<int, double>& neighborVector) {

bool updated = false;

for (const auto& [node, cost] : neighborVector) {

double newCost = cost + linkCost[node];

if (newCost < distanceVector[node]) {

distanceVector[node] = newCost;

nextHop[node] = node; // Update next-hop

updated = true;

}

}

if (updated) broadcastDistanceVector();

}

void broadcastDistanceVector() {

for (int i = 0; i < numNeighbors; i++) {

auto packet = new DistanceVectorPacket();

packet->setVector(distanceVector);

send(packet, “out”, i);

}

}

};

  1. Define Network Topology

Create a .ned File

  • Create the network topology using .ned file.
  • Example:

network BellmanFordNetwork

{

submodules:

node[5]: StandardHost {

parameters:

routingProtocol = “BellmanFordRouting”;

}

}

  1. Configure Simulation Parameters

Edit omnetpp.ini

  • Set the simulation metrics like topology, link costs, and simulation duration.

Example:

[Config BellmanFordSimulation]

network = BellmanFordNetwork

*.node[*].numNeighbors = 3

*.node[*].linkCost = uniform(1, 10)  # Random link costs

  1. Run the Simulation
  • In OMNeT++, execute the simulation to utilise the Tkenv or Cmdenv.
  • Monitor the routing table updates and packet flows.
  1. Analyze Results

Metrics to Evaluate

  • Convergence Time: Estimate the duration for every node to steady its routing tables.
  • Routing Overhead: Volume of packets that are swapped in the course of the convergence phase.
  • Path Optimality: Equate the calculated paths to the theoretical shortest paths.

Visualization

  • Make use of OMNeT++’s built-in tools, observing the distance vector exchanges and routing table updates.
  • Transfer information into external tools such as MATLAB or Python for advanced analysis.
  1. Extend and Optimize

Handle Dynamic Changes

  • Mimic scenarios in which:
    • Nodes join or leave the network.
    • Links fail.
  • Modernize the Bellman-Ford algorithm for dynamically managing these changes.

Enhance Efficiency

  • We need to execute the optimizations like:
    • Split Horizon: Prevent the routing loops by doesn’t transmitting data regarding a route again to the node from which it was studied.
    • Hold-Down Timers: Delay updates for routes that are marked as invalid.

Compare with Other Algorithms

  • We need to replicate and equate the Bellman-Ford including Dijkstra’s or Link-State Routing.

We have provided a structured approach and code snippets with OMNeT++ environment that contains simulation, analysis, evaluation, and visualization of Bellman Ford Routing Projects. For any additional insights, feel free to ask.

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