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# How to Calculate Network Stability Index in ns3

To calculate the stability index in ns3, we need to compute how stable a network over the time that encompasses metrics like link failure, node failure, packet loss or variation in throughput. The stability index is defined as the composite metric that includes numerous factors. Here is the step by procedure to compute the basic stability index in ns3:

Step-by-Step Implementation:

1. Set up Your Simulation Environment: Generate a network topology; organize nodes, links, and protocols.
2. Install Applications: To generate and receive traffic configures the application on the nodes.
3. Simulate Failures and Variations: Introduce link failures, node failures, or traffic variations.
4. Trace Packets and Collect Metrics: Use ns3 tracing capabilities to record relevant metrics such as packet loss, link status, and throughput.
5. Calculate Stability Index: Compute a composite stability index based on the collected metrics.

Example: Simple Stability Index Calculation

Here, we generate the basic network topology and measure the stability index, focused on packet loss and throughput variations.

Step 1: Set Up Your Simulation Environment

#include “ns3/core-module.h”

#include “ns3/network-module.h”

#include “ns3/internet-module.h”

#include “ns3/point-to-point-module.h”

#include “ns3/applications-module.h”

#include “ns3/error-model.h”

using namespace ns3;

NS_LOG_COMPONENT_DEFINE (“StabilityIndexExample”);

void PacketLossCallback (Ptr<const Packet> packet)

{

static uint32_t totalPacketsLost = 0;

totalPacketsLost++;

NS_LOG_UNCOND (“Total Packets Lost: ” << totalPacketsLost);

}

{

}

int main (int argc, char *argv[])

{

// Create two nodes

NodeContainer nodes;

nodes.Create (2);

// Set up the point-to-point link

PointToPointHelper pointToPoint;

pointToPoint.SetDeviceAttribute (“DataRate”, StringValue (“5Mbps”));

pointToPoint.SetChannelAttribute (“Delay”, StringValue (“2ms”));

// Install link devices on nodes

NetDeviceContainer devices = pointToPoint.Install (nodes);

// Create an error model

Ptr<RateErrorModel> em = CreateObject<RateErrorModel> ();

em->SetAttribute (“ErrorRate”, DoubleValue (0.01)); // 1% error rate

// Install the internet stack

InternetStackHelper stack;

stack.Install (nodes);

// Set up the UDP echo server on Node 1

uint16_t port = 9; // well-known echo port number

UdpEchoServerHelper echoServer (port);

ApplicationContainer serverApps = echoServer.Install (nodes.Get (1));

serverApps.Start (Seconds (1.0));

serverApps.Stop (Seconds (10.0));

// Set up the UDP echo client on Node 0

echoClient.SetAttribute (“MaxPackets”, UintegerValue (100));

echoClient.SetAttribute (“Interval”, TimeValue (Seconds (0.1))); // 10 packets per second

echoClient.SetAttribute (“PacketSize”, UintegerValue (1024));

ApplicationContainer clientApps = echoClient.Install (nodes.Get (0));

clientApps.Start (Seconds (2.0));

clientApps.Stop (Seconds (10.0));

// Connect packet loss trace to callback

devices.Get (1)->TraceConnectWithoutContext (“PhyRxDrop”, MakeCallback (&PacketLossCallback));

// Connect packet reception trace to callback

// Run the simulation

Simulator::Run ();

Simulator::Destroy ();

// Calculate stability index

uint32_t totalPacketsSent = 100; // Known number of packets sent

uint32_t totalPacketsLost = totalPacketsSent – totalPacketsReceived;

double packetLossRate = static_cast<double>(totalPacketsLost) / totalPacketsSent;

// Assume a hypothetical calculation of throughput variations

double throughputVariation = 0.05; // Example value

// Composite stability index (lower is better)

double stabilityIndex = packetLossRate + throughputVariation;

std::cout << “Total Packets Sent: ” << totalPacketsSent << std::endl;

std::cout << “Total Packets Lost: ” << totalPacketsLost << std::endl;

std::cout << “Packet Loss Rate: ” << packetLossRate * 100 << ” %” << std::endl;

std::cout << “Throughput Variation: ” << throughputVariation << std::endl;

std::cout << “Stability Index: ” << stabilityIndex << std::endl;

return 0;

}

Explanation

The given below are the detailed description for the stability index that are

1. Set Up Your Simulation Environment: Create two nodes and connect them with a point-to-point link.
2. Simulate Bit Errors: Attach a rate error model to the receiver node (Node 1) to simulate a 1% bit error rate.
3. Install Applications: download a UDP echo server on Node 1 and a UDP echo client on Node 0. Organise the client to send a specified number of packets at a specified interval.
4. Trace Packets and Collect Metrics: To count the number of packets lost and received by use of callback functions. Furthermore need to compute the throughput variation as required.
5. Calculate Stability Index: To compute a composite stability index by Syndicate the packet loss rate and throughput variations

Step-by-Step Breakdown

1. Create Nodes and Links: Two nodes are created and connected with a point-to-point link with a specified data rate and delay.
2. Configure Error Model: A rate error model is created and attached to the receiving device on Node 1, simulating a 1% bit error rate.
3. Install Internet Stack and Applications: The Internet stack is set up on the nodes, and a UDP echo server and client are set up to create and receive traffic.
4. Trace Packet Loss and Reception: Callback functions are used to count the number of packets lost and received.
5. Calculate Stability Index: The stability index is calculated by combining the packet loss rate and throughput variations.

Finally, we had implemented and computed the stability index in ns3 simulator. We also provide further insights into the performance of the stability index that across different simulation tools. If you’re having trouble finding a networking performance analysis, get in touch with ns3simulation.com, and we’ll support you in figuring out the Stability Index using the ns3 tool.