Introduction to ns-3 and AI Prompting

Hello World ns-3 Script 

Here is a simple ns-3 script that creates a basic network with two nodes and a point-to-point link. This is a great "Hello World" equivalent for network simulation.

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

// Bring in the ns3 namespace to avoid prefixing every class with "ns3::"
using namespace ns3;

int main(int argc, char *argv[]) {
    // 1. Create two nodes
    NodeContainer nodes;
    nodes.Create(2);

    // 2. Create a point-to-point channel and a link between the nodes
    PointToPointHelper pointToPoint;
    pointToPoint.SetDeviceAttribute("DataRate", StringValue("5Mbps"));
    pointToPoint.SetChannelAttribute("Delay", StringValue("2ms"));
    NetDeviceContainer devices;
    devices = pointToPoint.Install(nodes);

    // 3. Install the Internet stack on the nodes
    InternetStackHelper stack;
    stack.Install(nodes);

    // 4. Assign IP addresses
    Ipv4AddressHelper address;
    address.SetBase("10.1.1.0", "255.255.255.0");
    Ipv4InterfaceContainer interfaces = address.Assign(devices);

    // 5. Run the simulation
    Simulator::Run();
    Simulator::Destroy();

    return 0;
}

Explanation of the Code

1. Header Files and Namespace

• #include "ns3/...-module.h": These lines include the necessary header files for the ns-3 modules we will be using, such as the core, network, and point-to-point modules.

• using namespace ns3;: This line allows us to use ns-3 classes directly without the ns3:: prefix, making the code cleaner.

2. Main Function main()

• The main() function is the entry point of the program, just like in any other C++ application.

• int argc, char *argv[]: These are the standard command-line arguments that can be used to pass parameters to the simulation.

3. Creating Nodes

• NodeContainer nodes;: This creates an object to hold our nodes.

• nodes.Create(2);: This command creates two simulation nodes. In ns-3, a node is analogous to a computer or device.

4. Creating the Channel and Devices

• PointToPointHelper pointToPoint;: This is a "helper" class that simplifies the creation of a point-to-point link.

• SetDeviceAttribute(...) and SetChannelAttribute(...): These lines configure the link's properties, such as the data rate (5 Mbps) and propagation delay (2 ms).

• NetDeviceContainer devices;: This object will hold the network devices (e.g., network interface cards) for the nodes.

• devices = pointToPoint.Install(nodes);: This command creates the link and installs a network device on each of the two nodes.

5. Installing the Internet Stack

• InternetStackHelper stack;: This helper class simplifies the installation of the network stack (including TCP/IP, UDP, etc.) on the nodes.

• stack.Install(nodes);: This installs the full Internet protocol stack on both of our nodes, which is necessary for them to communicate.

6. Assigning IP Addresses

• Ipv4AddressHelper address;: This helper is used to assign IP addresses to the network devices.

• address.SetBase("10.1.1.0", "255.255.255.0");: This sets the network base and subnet mask for the IP addresses.

• Ipv4InterfaceContainer interfaces = address.Assign(devices);: This assigns IP addresses (e.g., 10.1.1.1 and 10.1.1.2) from the specified network to the two devices.

7. Running the Simulation

• Simulator::Run();: This is the most important command. It starts the discrete-event simulation, running all the scheduled events.

• Simulator::Destroy();: This cleans up all resources used by the simulation. It's good practice to call this at the end of every simulation.