Study the Effect of Buffer Size on Packet Loss in a Point-to-Point Router with UDP CBR Traffic

Problem Statement:

Study the effect of buffer size on packet loss in a point-to-point router with UDP CBR traffic.

Source Code:

#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/flow-monitor-module.h"
#include "ns3/netanim-module.h"
#include <fstream> // Required for writing data to the text file

using namespace ns3;

int main (int argc, char *argv[])
{
    // 1. Default Variables and Command Line Parsing
    uint32_t bufferSize = 10; // Default buffer size in packets
    CommandLine cmd;
    cmd.AddValue ("bufferSize", "Max number of packets in Queue", bufferSize);
    cmd.Parse (argc, argv);

    // 2. Node Creation
    NodeContainer nodes;
    nodes.Create (2);

    // 3. Point-to-Point Link Setup
    PointToPointHelper p2p;
    p2p.SetDeviceAttribute ("DataRate", StringValue ("2Mbps"));
    p2p.SetChannelAttribute ("Delay", StringValue ("2ms"));
    
    // Applying the Buffer Size (Queue Limit)
    p2p.SetQueue ("ns3::DropTailQueue", "MaxSize", QueueSizeValue (QueueSize (QueueSizeUnit::PACKETS, bufferSize)));

    NetDeviceContainer devices = p2p.Install (nodes);

    // 4. Internet Stack and IP Assignment
    InternetStackHelper stack;
    stack.Install (nodes);

    Ipv4AddressHelper address;
    address.SetBase ("10.1.1.0", "255.255.255.0");
    Ipv4InterfaceContainer interfaces = address.Assign (devices);

    // 5. Application Setup (UDP CBR Traffic at 5Mbps to force drops)
    uint16_t port = 9;
    OnOffHelper onoff ("ns3::UdpSocketFactory", Address (InetSocketAddress (interfaces.GetAddress (1), port)));
    onoff.SetConstantRate (DataRate ("5Mbps")); 
    onoff.SetAttribute ("PacketSize", UintegerValue (1024));

    ApplicationContainer apps = onoff.Install (nodes.Get (0));
    apps.Start (Seconds (1.0));
    apps.Stop (Seconds (10.0));

    // 6. NetAnim Configuration
    AnimationInterface anim ("24BPS1020.xml"); // Your XML file name
    anim.SetConstantPosition (nodes.Get (0), 10.0, 50.0);
    anim.SetConstantPosition (nodes.Get (1), 90.0, 50.0);

    // 7. Flow Monitor Setup
    FlowMonitorHelper flowmon;
    Ptr<FlowMonitor> monitor = flowmon.InstallAll ();

    // 8. Run Simulation
    Simulator::Stop (Seconds (11.0));
    Simulator::Run ();

    // 9. Results Extraction and File Writing
    monitor->CheckForLostPackets ();
    Ptr<Ipv4FlowClassifier> classifier = DynamicCast<Ipv4FlowClassifier> (flowmon.GetClassifier ());
    std::map<FlowId, FlowMonitor::FlowStats> stats = monitor->GetFlowStats ();

    // Open a file to append the data for your graph
    std::ofstream dataset;
    dataset.open ("loss_data.txt", std::ios_base::app);

    // Loop through the flows to print and save stats
    for (std::map<FlowId, FlowMonitor::FlowStats>::const_iterator i = stats.begin (); i != stats.end (); ++i)
    {
        double lossRatio = (double)i->second.lostPackets / i->second.txPackets * 100;
        
        // Print Output to Terminal
        std::cout << "Buffer Size: " << bufferSize << " Packets" << std::endl;
        std::cout << "Packets Transmitted: " << i->second.txPackets << std::endl;
        std::cout << "Packets Received: " << i->second.rxPackets << std::endl;
        std::cout << "Packets Lost: " << i->second.lostPackets << std::endl;
        std::cout << "Packet Loss Ratio: " << lossRatio << "%" << std::endl;
        std::cout << "-----------------------------------" << std::endl;

        // Write directly to the text file (Format: BufferSize LossPercentage)
        dataset << bufferSize << " " << lossRatio << std::endl;
    }
    
    dataset.close (); // Close the text file

    // 10. Cleanup
    Simulator::Destroy ();
    return 0;
}

Output:

Commands & Execution Runs:

./ns3 run "scratch/24BPS1020.cc --bufferSize=5"

./ns3 run "scratch/24BPS1020.cc --bufferSize=10"

./ns3 run "scratch/24BPS1020.cc --bufferSize=25"

./ns3 run "scratch/24BPS1020.cc --bufferSize=50"

NetAnim Visualization:

NetAnim simulation showing point-to-point traffic flow. The NetAnim visualizer depicts the fundamental network topology and runtime environment generated by the ns-3 simulation script.

GNU Plot:

The generated graph plots the Packet Loss Ratio (represented as a percentage on the Y-axis) against the Router's Buffer Size (represented as the number of packets in the DropTailQueue on the X-axis) for a point-to-point network link.

LLM Information:

LLM Used: Gemini (Google AI)

Prompt Provided:

Study the effect of buffer size on packet loss in a point-to-point router with UDP CBR traffic. explain what has to be. You need to design a network as per the Question given in the following Excel sheet. The exercises were allotted to students based on randomisation within an Excel sheet. You need to submit the following: ... these are the instruction provided and the topic is already given. description of the output graph. similarly, for netanim.