How to Implement Consensus Protocol in OMNeT++

To implement the Consensus Protocol in OMNeT++, we have to simulate a network which contains multiple nodes that must decide on a certain value, state, or decision, usually used in dispersed systems like blockchain, scattered databases, and fault-tolerant systems. This protocol makes sure that even when some nodes fail or behaves maliciously, the proper consensus is still reached. Follow the step-by-step approach provided in the below:

Step-by-Step Implementation:

Set Up OMNeT++ and INET Framework

Install OMNeT++: Make certain to install the OMNeT++ and configured.
Install INET Framework: Download and install the INET framework that offers network models and simple communication protocols.

Define the Network Topology

Begin by generating a network topology that has multiple nodes which will participate in the consensus protocol. It indicates servers in a dispersed system, nodes in a blockchain network, or other entities needing consensus.

Example NED File (ConsensusNetwork.ned):

package mynetwork;

import inet.node.inet.StandardHost;

import inet.node.inet.Router;

network ConsensusNetwork

{

parameters:

int numNodes = default(5); // Number of nodes in the network

submodules:

node[numNodes]: StandardHost {

@display(“p=100,100;is=square,red”);

}

router: Router {

@display(“p=300,200”);

}

connections allowunconnected:

for i = 0..numNodes-1 {

node[i].ethg++ <–> ethernetLine <–> router.ethg++;

}

In this sample:

node[]: Donates the nodes contributing in the consensus protocol.
router: Acts as a central router facilitating communication among the nodes.

Create a Consensus Protocol

Simulate a simple consensus mechanism like Byzantine Fault Tolerance (BFT), Paxos, or Proof of Work (PoW) by generating a custom consensus protocol.

Example: Basic Consensus Protocol (ConsensusProtocol.ned)

package mynetwork;

import inet.applications.base.ApplicationBase;

simple ConsensusProtocol extends ApplicationBase

{

gates:

input upperLayerIn;

output upperLayerOut;

input lowerLayerIn;

output lowerLayerOut;

}

ConsensusProtocol.cc (Basic Implementation)

#include “inet/common/INETDefs.h”

#include “inet/applications/base/ApplicationBase.h”

#include <map>

Define_Module(ConsensusProtocol);

void ConsensusProtocol::initialize(int stage) {

ApplicationBase::initialize(stage);

if (stage == INITSTAGE_LOCAL) {

consensusTimer = new cMessage(“consensusTimer”);

scheduleAt(simTime() + par(“startDelay”).doubleValue(), consensusTimer);

valueToPropose = par(“valueToPropose”).intValue();

}

void ConsensusProtocol::handleMessageWhenUp(cMessage *msg) {

if (msg == consensusTimer) {

initiateConsensus();

} else if (msg->getArrivalGate() == lowerLayerIn) {

handleConsensusMessage(msg);

}

void ConsensusProtocol::initiateConsensus() {

EV << “Node ” << getParentModule()->getIndex() << ” initiating consensus with value: ” << valueToPropose << “\n”;

// Send proposed value to all other nodes

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

cMessage *proposalMsg = new cMessage(“ConsensusProposal”);

proposalMsg->addPar(“value”) = valueToPropose;

send(proposalMsg, “lowerLayerOut”, i);

}

void ConsensusProtocol::handleConsensusMessage(cMessage *msg) {

int receivedValue = msg->par(“value”);

EV << “Node ” << getParentModule()->getIndex() << ” received proposed value: ” << receivedValue << “\n”;

// Simulate voting or consensus logic

consensusVotes[receivedValue]++;

delete msg;

// Check if consensus is reached

if (consensusVotes[receivedValue] > (gateSize(“lowerLayerOut”) / 2)) {

EV << “Consensus reached on value: ” << receivedValue << “\n”;

}

void ConsensusProtocol::finish() {

cancelAndDelete(consensusTimer);

}

In this instance:

valueToPropose: Signifies the value a node proposes in the course of consensus process.
consensusVotes: A map that search how many nodes have voted for every anticipated value.
initiateConsensus(): Begins the consensus process by broadcasting the proposed value to all other nodes.
handleConsensusMessage(): Receives and progressions consensus messages from other nodes.

Configure the Simulation

Use custom consensus protocol by configuring the simulation in the omnetpp.ini file.

Example Configuration in omnetpp.ini:

network = ConsensusNetwork

**.node[*].applications[0].typename = “ConsensusProtocol”

**.node[*].applications[0].startDelay = 10s # Delay before starting consensus

**.node[*].applications[0].valueToPropose = 42 # Value to propose for consensus

Run the Simulation

Run the simulation and see how the nodes start the consensus process, broadcast their proposed values, and reach consensus. The logs should signify when consensus is reached and on which value.

Analyze the Consensus Process

After running the simulation, analyze how the consensus process clarifies:

Consensus Speed: Estimate the time taken for the network to reach consensus.
Robustness: Examine the protocol’s robustness by presenting failures or malicious nodes.
Scalability: Research with various network sizes to see how well the protocol scales.

Extend the Consensus Protocol

You can extend the basic consensus protocol with more advanced features like:

Fault Tolerance: Manage node failures or Byzantine faults by executing mechanisms.
Leader Election: Acquaint with a leader election process for consensus protocols like Paxos.
Weighted Voting: Execute weighted voting where some nodes have more impact on the consensus outcome.

Example: Adding Fault Tolerance (Byzantine Fault Tolerance)

void ConsensusProtocol::handleConsensusMessage(cMessage *msg) {

int receivedValue = msg->par(“value”);

EV << “Node ” << getParentModule()->getIndex() << ” received proposed value: ” << receivedValue << “\n”;

// Simulate Byzantine behavior (e.g., a node could send conflicting values)

if (uniform(0, 1) < 0.1) { // 10% chance of Byzantine fault

receivedValue = intuniform(0, 100); // Random conflicting value

EV << “Byzantine node! Sending conflicting value: ” << receivedValue << “\n”;

}