Section outline

  • The Following is a simple ns-3 simulation that creates a point-to-point link between two nodes, runs a UDP echo client-server application, and generates a visualization file for NetAnim. Follow the comments to understand each step.

    #include "ns3/core-module.h"
#include "ns3/network-module.h"
#include "ns3/point-to-point-module.h"
#include "ns3/internet-module.h"
#include "ns3/applications-module.h"
#include "ns3/mobility-module.h"
#include "ns3/netanim-module.h"

using namespace ns3;

int main(int argc, char *argv[])
{
    // Create a container to hold our two nodes
    NodeContainer nodes;
    nodes.Create(2);

    // Create a point-to-point channel and configure its attributes
    PointToPointHelper channel;
    channel.SetDeviceAttribute("DataRate", StringValue("5Mbps"));
    channel.SetChannelAttribute("Delay", StringValue("2ms"));

    // Install the channel and devices on our nodes
    NetDeviceContainer netDevices;
    netDevices = channel.Install(nodes);

    // Install the Internet stack (TCP/IP) on our nodes
    InternetStackHelper ipStack;
    ipStack.Install(nodes);

    // Assign IP addresses to the devices
    Ipv4AddressHelper ipAddresses;
    ipAddresses.SetBase("192.168.1.0", "255.255.255.0");
    Ipv4InterfaceContainer ipinterfaces = ipAddresses.Assign(netDevices);

    // Set up a UDP Echo Server on node 1, listening on port 9
    UdpEchoServerHelper udpEchoServer(9);
    ApplicationContainer serverApps = udpEchoServer.Install(nodes.Get(1));
    serverApps.Start(Seconds(1.0));

    // Set up a UDP Echo Client on node 0
    UdpEchoClientHelper udpEchoClient(ipinterfaces.GetAddress(1), 9);
    ApplicationContainer clientApps = udpEchoClient.Install(nodes.Get(0));
    clientApps.Start(Seconds(2.0));

    // Set up NetAnim to visualize the simulation
    AnimationInterface anim("SimpleNS3Simulation_NetAnimationOutput.xml");
    anim.SetConstantPosition(nodes.Get(0), 0, 5);
    anim.SetConstantPosition(nodes.Get(1), 10, 5);

    // Run the simulation
    Simulator::Run();
    Simulator::Destroy();
    return 0;
}

    Step-by-Step Explanation

    1. Setup and Topology

    The script first sets up the fundamental elements of the simulation.

    • Header Files: Necessary modules for core functionality, networking, point-to-point links, the internet stack, applications, mobility, and NetAnim are included.

    • Node Creation: A NodeContainer is used to create two virtual nodes, which act as the endpoints of our network.

    • Channel and Device Configuration: A PointToPointHelper sets up a communication channel with a specified DataRate (5 Mbps) and Delay (2 ms) and installs network devices on the nodes

    2. Network Stack and Addressing

    This section transforms the generic nodes into functional network devices.

    • IP Stack Installation: The InternetStackHelper installs the full IP stack on both nodes, enabling them to use IP addresses and handle protocols like TCP and UDP.

    • IP Address Assignment: An Ipv4AddressHelper assigns IP addresses from the 192.168.1.0/24 subnet to the network devices, making them addressable.

    3. Application Layer

    This part configures the actual data traffic for the simulation.

    • UDP Echo Server: A UdpEchoServerHelper sets up an application on the second node to listen for UDP packets on port 9.

    • UDP Echo Client: A UdpEchoClientHelper sets up a client on the first node to send packets to the server's IP address.

    • Event Scheduling: Both applications are scheduled to start at different times. The server starts at 1 second, ensuring it's ready to receive before the client begins sending at 2 seconds.

    4. Mobility and Visualization

    This is a key addition to the basic simulation, allowing for a visual representation of the network.

    • Mobility Helper (Commented): The MobilityHelper section is included in your original code but is redundant and commented out. ConstantPositionMobilityModel is used to set static positions, but the subsequent NetAnim calls override this.

    • AnimationInterface: An AnimationInterface object is created, which will generate an XML file (SimpleNS3Simulation_NetAnimationOutput.xml) containing all the events needed for the NetAnim visualizer.

    • Static Positioning: The SetConstantPosition() function explicitly sets the coordinates for each node on the NetAnim canvas, with Node 0 at (0, 5) and Node 1 at (10, 5).

    5. Start Running the Simulation

    • Running the Simulation: Simulator::Run() starts the simulation, processing all scheduled events.

    • Cleanup: Simulator::Destroy() is a good practice to free up all memory and objects, ensuring a clean exit.

    • Return Value: The return 0; statement indicates a successful program execution.