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How to Implement Tree Topology in ns3

To implement a tree topology in ns3, we need to create a hierarchical network structure where each node is connected to one or more child nodes, and there is a single root node. Below is the step-by-step guide to implement tree topology in ns3.

Steps to implement tree topology

  1. Set Up ns3:
    • Make sure that ns3 is installed in the computer. If not, install it.
  2. Create the Nodes:
    • To represent the root, intermediate, and leaf nodes in the tree network, create a set of nodes.
  3. Set Up the Point-to-Point Channels:
    • To connect each node to its child nodes, forming a tree structure, use point-to-point helpers.
  4. Install Network Stack:
    • On all nodes, install the internet stack.
  5. Assign IP Addresses:
    • To the nodes connected to the point-to-point links, assign IP addresses.
  6. Set Up Applications:
    • To generate traffic and demonstrate communication between nodes, install applications.

Example code

Here is an example to set up a basic tree topology in ns3.

#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”

using namespace ns3;

NS_LOG_COMPONENT_DEFINE (“TreeTopologyExample”);

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

{

CommandLine cmd;

cmd.Parse (argc, argv);

// Create nodes

NodeContainer nodes;

nodes.Create (7); // Create 7 nodes for the tree (1 root, 2 intermediate, 4 leaves)

// Create point-to-point links

PointToPointHelper pointToPoint;

pointToPoint.SetDeviceAttribute (“DataRate”, StringValue (“100Mbps”));

pointToPoint.SetChannelAttribute (“Delay”, TimeValue (NanoSeconds (6560)));

NetDeviceContainer devices;

InternetStackHelper stack;

stack.Install (nodes);

// Helper function to connect two nodes and assign IP addresses

auto connectNodes = [&](uint32_t parent, uint32_t child, uint32_t subnet) {

NetDeviceContainer link = pointToPoint.Install (NodeContainer (nodes.Get (parent), nodes.Get (child)));

devices.Add (link);

std::ostringstream subnetStream;

subnetStream << “10.1.” << subnet << “.0”;

Ipv4AddressHelper address;

address.SetBase (subnetStream.str ().c_str (), “255.255.255.0”);

address.Assign (link);

};

// Connect the nodes to form a tree

connectNodes(0, 1, 1); // Root to intermediate

connectNodes(0, 2, 2); // Root to intermediate

connectNodes(1, 3, 3); // Intermediate to leaf

connectNodes(1, 4, 4); // Intermediate to leaf

connectNodes(2, 5, 5); // Intermediate to leaf

connectNodes(2, 6, 6); // Intermediate to leaf

// Enable routing

Ipv4GlobalRoutingHelper::PopulateRoutingTables ();

// Create a UDP server on one of the leaf nodes

UdpServerHelper udpServer (9);

ApplicationContainer serverApp = udpServer.Install (nodes.Get (3));

serverApp.Start (Seconds (1.0));

serverApp.Stop (Seconds (10.0));

// Create a UDP client on the root node

UdpClientHelper udpClient (Ipv4Address (“10.1.3.2”), 9); // Assuming node 3’s IP is 10.1.3.2

udpClient.SetAttribute (“MaxPackets”, UintegerValue (320));

udpClient.SetAttribute (“Interval”, TimeValue (MilliSeconds (50)));

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

ApplicationContainer clientApp = udpClient.Install (nodes.Get (0));

clientApp.Start (Seconds (2.0));

clientApp.Stop (Seconds (10.0));

// Enable packet capture

pointToPoint.EnablePcapAll (“tree-topology”);

// Enable logging

LogComponentEnable (“UdpClient”, LOG_LEVEL_INFO);

LogComponentEnable (“UdpServer”, LOG_LEVEL_INFO);

Simulator::Run ();

Simulator::Destroy ();

return 0;

}

Explanation

  1. Setup:

Created seven node and those nodes connected by point-to-point links to set up a tree topology.

  1. Point-to-Point Links:

To connect the root node to the intermediate nodes and the intermediate nodes to the leaf nodes, forming a tree structure, Point-to-point links are created. The data rate and delay are configured for the links.

  1. Network Stack:

On all nodes, the internet stack is installed.

  1. IP Addresses:

To the nodes, IP addresses are assigned connected by the point-to-point links.

  1. Applications:

On one of the leaf nodes (node 3), A UDP server is installed and a UDP client is installed on the root node (node 0) to generate traffic and demonstrate communication.

  1. Packet Capture:

To observe network traffic, packet capture is enabled for the point-to-point links.

  1. Logging:

To provide detailed output during the simulation, logging is enabled for the UDP client and server applications.

Running the Simulation

Compile and run the simulation using the following commands.

./waf configure

./waf build

./waf –run tree-topology-example

Replace tree-topology-example with the actual name of your script file.

On the whole we had our implementation results on tree topology by creating hierarchical network structure where each node is connected to one or more child nodes, and with a single root node. Also, we provide more related content on Tree topology.

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