Simulation of persistent vs. non-persistent CSMA in a 15-node wired LAN and compare channel utilization | NS3 Project 9

Computer Networks Digital Assignment

Topic:

Simulate persistent vs. non-persistent CSMA in a 15-node wired LAN and compare channel utilization.

Code:

// csma-persistent.cc
#include "ns3/core-module.h"
#include "ns3/network-module.h"
#include "ns3/csma-module.h"
#include "ns3/internet-module.h"
#include "ns3/applications-module.h"
#include "ns3/netanim-module.h"
#include "ns3/flow-monitor-module.h"

using namespace ns3;

NS_LOG_COMPONENT_DEFINE("CsmaSimulation");

int main (int argc, char *argv[])
{
  bool persistent = true; // change to false for non-persistent
  CommandLine cmd;
  cmd.AddValue("persistent", "Enable persistent CSMA", persistent);
  cmd.Parse(argc, argv);

  NodeContainer nodes;
  nodes.Create(15);

  CsmaHelper csma;
  csma.SetChannelAttribute("DataRate", StringValue("100Mbps"));
  csma.SetChannelAttribute("Delay", TimeValue(NanoSeconds(6560)));

  NetDeviceContainer devices = csma.Install(nodes);

  InternetStackHelper stack;
  stack.Install(nodes);

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

  uint16_t port = 9;

  // Server on node 0
  UdpServerHelper server(port);
  ApplicationContainer serverApp = server.Install(nodes.Get(0));
  serverApp.Start(Seconds(1.0));
  serverApp.Stop(Seconds(20.0));

  // Clients on remaining nodes
  for (int i = 1; i < 15; i++)
  {
    UdpClientHelper client(interfaces.GetAddress(0), port);
    client.SetAttribute("MaxPackets", UintegerValue(1000));
    client.SetAttribute("Interval",
                        TimeValue(persistent ? Seconds(0.01) : Seconds(0.05))); // key difference
    client.SetAttribute("PacketSize", UintegerValue(1024));

    ApplicationContainer clientApp = client.Install(nodes.Get(i));
    clientApp.Start(Seconds(2.0 + i * 0.1));
    clientApp.Stop(Seconds(20.0));
  }

  // Enable tracing
  csma.EnablePcapAll("csma");

  // NetAnim
  std::string mode = persistent ? "persistent" : "nonpersistent";
  AnimationInterface anim("csma-" + mode + ".xml");

  // PCAP trace file
  csma.EnablePcapAll("csma-" + mode);

  Simulator::Stop(Seconds(20.0));

  FlowMonitorHelper flowmon;
  Ptr<FlowMonitor> monitor = flowmon.InstallAll();

  Simulator::Run();
  monitor->CheckForLostPackets();

  Ptr<Ipv4FlowClassifier> classifier = DynamicCast<Ipv4FlowClassifier>(flowmon.GetClassifier());
  std::map<FlowId, FlowMonitor::FlowStats> stats = monitor->GetFlowStats();

  for (auto &flow : stats)
  {
    std::cout << "Flow ID: " << flow.first << std::endl;
    std::cout << "Tx Packets: " << flow.second.txPackets << std::endl;
    std::cout << "Rx Packets: " << flow.second.rxPackets << std::endl;
    std::cout << "Throughput: " << flow.second.rxBytes * 8.0 /
      (flow.second.timeLastRxPacket.GetSeconds() -
       flow.second.timeFirstTxPacket.GetSeconds()) / 1024 << " Kbps\n";
  }

  Simulator::Destroy();
  return 0;
}

Commands to run the code:

1. Create a file inside the scratch folder and save the code as csma-persistent.cc.
2. To run code in persistent mode:

   ./ns3 run "scratch/csma-persistent --persistent=1"

3. To run code in non-persistent mode:

   ./ns3 run "scratch/csma-persistent --persistent=0"

4. Generated Output Files:
   • For Persistent:
     • csma-persistent.xml
     • csma-persistent-*.pcap
   • For Non-Persistent:
     • csma-nonpersistent.xml
     • csma-nonpersistent-*.pcap

Output:

For Non-Persistent:

For Persistent:

Graph: