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How to Implement bellman ford routing in OMNeT++

To implement the Bellman-Ford routing algorithm in OMNeT++, Use Bellman-ford algorithm to create a network in which all nodes calculate the shortest paths to all other nodes. Based on the information offered by nearest nodes, this algorithm updates the routing information which is also called distance-vector routing protocol. We work on all projects regarding to Bellman-Ford routing algorithm in OMNeT++ program .

Here’s a step-by-step guide on how to implement Bellman-Ford routing in OMNeT++ using the INET framework.

Step-by-Step Implementation:

Step 1: Set Up OMNeT++ and INET Framework

  1. Install OMNeT++:
    • Make sure OMNeT++ is installed on your system. You can download it from the OMNeT++
  2. Install the INET Framework:
    • Download and install the INET Framework, which offers different networking protocols and models. INET can be downloaded from the INET GitHub repository.

Step 2: Create a New OMNeT++ Project

  1. Create the Project:
    • Open OMNeT++ and create a new OMNeT++ project via File > New > OMNeT++ Project.
    • Name it (like BellmanFordRoutingSimulation) and set up the project directory.
  2. Set Up Project Dependencies:
    • Make certain the project references the INET Framework by right-clicking on your project in the Project Explorer, navigating to Properties > Project References, and checking the INET project.

Step 3: Define the Network Topology

  1. Create a NED File:
    • Use NED language to state the network topology which contains routers or nodes that will use the Bellman-Ford algorithm.

Example:

network BellmanFordNetwork

{

submodules:

router1: Router;

router2: Router;

router3: Router;

router4: Router;

connections:

router1.ethg++ <–> Eth10Mbps <–> router2.ethg++;

router2.ethg++ <–> Eth10Mbps <–> router3.ethg++;

router3.ethg++ <–> Eth10Mbps <–> router4.ethg++;

router4.ethg++ <–> Eth10Mbps <–> router1.ethg++;

}

  1. Configure Network Parameters:
    • Build the necessary link parameters like bandwidth, delay, and packet loss to simulate a realistic network environment.

Step 4: Implement the Bellman-Ford Routing Protocol

  1. Define the Bellman-Ford Module:
    • For bellman-ford routing protocol, we have to generate a new module in NED. This module will manages the routing decisions according to the Bellman-Ford algorithm.

Example (in NED):

simple BellmanFordRouting

{

parameters:

@display(“i=block/network2”);

gates:

inout lowerLayerIn[];

inout lowerLayerOut[];

}

  1. Implement Bellman-Ford Logic in C++:
    • Execute the Bellman-Ford routing logic in C++. This involves maintaining a routing table, updating it as per the information received from nearest nodes, and broadcasting updates.

Example (C++ implementation):

#include “inet/common/INETDefs.h”

#include “inet/networklayer/contract/IRoutingTable.h”

#include “inet/networklayer/ipv4/IPv4RoutingTable.h”

class BellmanFordRouting : public cSimpleModule

{

private:

struct RouteEntry {

double cost;

std::string nextHop;

};

std::map<std::string, RouteEntry> routingTable;  // Destination -> (Cost, Next Hop)

IRoutingTable *inetRoutingTable;

protected:

virtual void initialize() override;

virtual void handleMessage(cMessage *msg) override;

void broadcastRoutingTable();

void processRoutingUpdate(cMessage *msg);

void updateRoutingTable(const std::string& destination, double cost, const std::string& nextHop);

};

Define_Module(BellmanFordRouting);

void BellmanFordRouting::initialize() {

inetRoutingTable = getModuleFromPar<IRoutingTable>(par(“routingTableModule”), this);

// Initialize the routing table

// Assuming a direct mapping between interfaces and neighbors

for (int i = 0; i < gateSize(“lowerLayerOut”); i++) {

std::string neighbor = “router” + std::to_string(i + 1);

routingTable[neighbor] = {1.0, neighbor};  // Cost to direct neighbors is 1.0

}

// Start by broadcasting the initial routing table

broadcastRoutingTable();

}

 

void BellmanFordRouting::handleMessage(cMessage *msg) {

if (msg->arrivedOn(“lowerLayerIn”)) {

processRoutingUpdate(msg);

}

}

void BellmanFordRouting::broadcastRoutingTable() {

// Send the current routing table to all neighbors

for (int i = 0; i < gateSize(“lowerLayerOut”); i++) {

cMessage *update = new cMessage(“RoutingUpdate”);

// Package the routing table information into the message

// Example: Add the routing table entries to the message’s control info

for (auto &entry : routingTable) {

// Add each entry to the update message

// You may need a custom control info or message subclass

}

send(update, “lowerLayerOut”, i);

}

}

void BellmanFordRouting::processRoutingUpdate(cMessage *msg) {

// Extract the routing information from the received message

// Update the routing table based on the received data

std::string neighbor = “some_neighbor”;  // Extracted from msg

double costToNeighbor = 1.0;  // Extracted from msg

for (auto &entry : routingTable) {

double newCost = costToNeighbor + entry.second.cost;

updateRoutingTable(entry.first, newCost, neighbor);

}

// Optionally, rebroadcast the updated routing table

broadcastRoutingTable();

delete msg;

}

void BellmanFordRouting::updateRoutingTable(const std::string& destination, double cost, const std::string& nextHop) {

if (routingTable.find(destination) == routingTable.end() || routingTable[destination].cost > cost) {

routingTable[destination] = {cost, nextHop};

EV << “Updated route to ” << destination << ” via ” << nextHop << ” with cost ” << cost << endl;

}

}

    • Routing Table: The module handles a routing table where all entry has the cost to reach a destination and the next hop to use.
    • Broadcasting Updates: The module occasionally broadcasts its routing table to neighboring nodes.
    • Processing Updates: When a node receives a routing update, it processes the information to potentially update its own routing table.

Step 5: Set Up the Simulation

  1. Configure the Simulation in omnetpp.ini:
    • Configure the simulation parameters like simulation time, network settings, and traffic patterns.

Example:

network = BellmanFordNetwork

sim-time-limit = 100s

**.scalar-recording = true

**.vector-recording = true

# Application traffic configuration (if needed)

*.router1.numApps = 1

*.router1.app[0].typename = “UdpBasicApp”

*.router1.app[0].destAddress = “router3”

*.router1.app[0].destPort = 5000

*.router1.app[0].messageLength = 1024B

*.router1.app[0].sendInterval = uniform(1s, 2s)

  1. Traffic Configuration:
    • To accelerate the bellman-ford routing updates and generate network activity, we have to configure the application-level traffic between nodes.

Step 6: Run the Simulation

  1. Compile the Project:
    • Ensure everything is properly executed and compiled.
  2. Run Simulations:
    • Use OMNeT++’s IDE or command line to implement the simulation. Observe the characteristics of the Bellman-Ford routing protocol, particularly how routes are accomplished and updated over time.

Step 7: Analyze the Results

  1. Monitor Routing Convergence:
    • Analyze how quickly and efficiently the network converges to stable routing paths with the help of the Bellman-Ford algorithm.
  2. Evaluate Protocol Performance:
    • Evaluate key performance metrics includes route optimality, network utilization, and convergence time.
    • Scalars and Vectors: Use OMNeT++ tools to record and analyze scalar and vector data like the amount of routing updates, the total number of hops, and the time taken to reach destinations.
  3. Check for Issues:
    • Search for issues like routing loops or instability, which can occur if the network topology changes constantly.

Step 8: Refine and Optimize the Protocol

  1. Address Any Bugs or Inefficiencies:
    • If the protocol exhibits problems like routing loops or slow convergence, consider developing enhancements like split horizon or route poisoning to preclude these issues.
  2. Optimize for Performance:
    • Adjust the parameters like update intervals or damping mechanisms to optimize performance through many network conditions.
  3. Re-Test:
    • Run the simulation again with the optimized protocol to certify developments.

From this procedure, we successfully showcased the important information to implement the basic network and bellman-ford routing in the OMNeT++. If needed, we can guide you through the additional simulation process of BFR.

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