To implement a logical topology using NS3 we need to replicate the abstract links among the nodes that could not directly reflect the physical associations. Logical topologies are denoting how data flows among the nodes in spite of the physical arrangement. Below is a detailed guide to get started:
Steps to Begin Implement Logical Topology in NS3
- Understand Logical Topologies
- Logical topology is according to the data flow or interaction paths among the nodes.
- Instance of logical topologies:
- Star: A central hub interacts with every node.
- Ring: These nodes communicate within a circular arrangement.
- Mesh: Logically each node associates to every other node.
- Custom: Arbitrary logical connections among the nodes.
- Set Up NS3
- Install NS3:
- We should install and download NS3 environment on the system.
- Test the installation by executing:
./waf –run hello-simulator
- Install Wireshark:
- Examine the network traffic with the help of .pcap files in wireshark.
- Design a Logical Topology
A logical topology can be executed by point-to-point links, CSMA, or a mix which is relying on the required structure.
Example 1: Logical Star Topology
In a star topology:
- One node performs like a central hub.
- All other nodes only interact with the hub.
NodeContainer nodes;
nodes.Create(5); // 1 hub + 4 spokes
PointToPointHelper p2p;
p2p.SetDeviceAttribute(“DataRate”, StringValue(“10Mbps”));
p2p.SetChannelAttribute(“Delay”, StringValue(“2ms”));
NetDeviceContainer devices;
for (uint32_t i = 1; i < nodes.GetN(); ++i) {
devices.Add(p2p.Install(nodes.Get(0), nodes.Get(i))); // Hub is node 0
}
InternetStackHelper stack;
stack.Install(nodes);
Ipv4AddressHelper address;
for (uint32_t i = 0; i < devices.GetN(); i += 2) {
std::ostringstream subnet;
subnet << “192.168.” << i / 2 + 1 << “.0”;
address.SetBase(subnet.str().c_str(), “255.255.255.0”);
address.Assign(NetDeviceContainer(devices.Get(i), devices.Get(i + 1)));
}
Example 2: Logical Ring Topology
In a ring topology:
- Every single node is linked to two neighbors to make a loop.
NodeContainer nodes;
nodes.Create(6); // Create 6 nodes in a ring
PointToPointHelper p2p;
p2p.SetDeviceAttribute(“DataRate”, StringValue(“10Mbps”));
p2p.SetChannelAttribute(“Delay”, StringValue(“2ms”));
NetDeviceContainer devices;
for (uint32_t i = 0; i < nodes.GetN(); ++i) {
devices.Add(p2p.Install(nodes.Get(i), nodes.Get((i + 1) % nodes.GetN()))); // Connect in a loop
}
InternetStackHelper stack;
stack.Install(nodes);
Ipv4AddressHelper address;
for (uint32_t i = 0; i < devices.GetN(); i += 2) {
std::ostringstream subnet;
subnet << “192.168.” << i / 2 + 1 << “.0”;
address.SetBase(subnet.str().c_str(), “255.255.255.0”);
address.Assign(NetDeviceContainer(devices.Get(i), devices.Get(i + 1)));
}
Example 3: Logical Mesh Topology
In a mesh topology:
- Logically all other node interacted by each node.
NodeContainer nodes;
nodes.Create(4); // Create 4 nodes
PointToPointHelper p2p;
p2p.SetDeviceAttribute(“DataRate”, StringValue(“10Mbps”));
p2p.SetChannelAttribute(“Delay”, StringValue(“2ms”));
NetDeviceContainer devices;
for (uint32_t i = 0; i < nodes.GetN(); ++i) {
for (uint32_t j = i + 1; j < nodes.GetN(); ++j) {
devices.Add(p2p.Install(nodes.Get(i), nodes.Get(j)));
}
}
InternetStackHelper stack;
stack.Install(nodes);
Ipv4AddressHelper address;
for (uint32_t i = 0; i < devices.GetN(); i += 2) {
std::ostringstream subnet;
subnet << “192.168.” << i / 2 + 1 << “.0”;
address.SetBase(subnet.str().c_str(), “255.255.255.0”);
address.Assign(NetDeviceContainer(devices.Get(i), devices.Get(i + 1)));
}
- Assign Logical Roles
Set up applications or routes for describing the data flow after configuring the logical connections.
Example Application for Communication
We should install applications at nodes for replicating the communication.
UdpEchoServerHelper echoServer(9);
ApplicationContainer serverApps = echoServer.Install(nodes.Get(0)); // Node 0 is the server
serverApps.Start(Seconds(1.0));
serverApps.Stop(Seconds(10.0));
UdpEchoClientHelper echoClient(Ipv4Address(“192.168.1.1”), 9);
echoClient.SetAttribute(“MaxPackets”, UintegerValue(5));
echoClient.SetAttribute(“Interval”, TimeValue(Seconds(1.0)));
echoClient.SetAttribute(“PacketSize”, UintegerValue(1024));
ApplicationContainer clientApps = echoClient.Install(nodes.Get(2)); // Node 2 is the client
clientApps.Start(Seconds(2.0));
clientApps.Stop(Seconds(10.0));
- Enable Tracing
Allow tracing to seize the packets for packet inspection:
p2p.EnablePcapAll(“logical-topology”);
- Run the Simulation
Build and run the simulation script in logical topology:
./waf –run logical-topology
- Example Code Skeleton
Below is a sample NS3 script for implementing a star logical topology:
#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;
int main(int argc, char *argv[]) {
// Create nodes
NodeContainer nodes;
nodes.Create(5); // 1 hub + 4 spokes
// Configure Point-to-Point links
PointToPointHelper p2p;
p2p.SetDeviceAttribute(“DataRate”, StringValue(“10Mbps”));
p2p.SetChannelAttribute(“Delay”, StringValue(“2ms”));
NetDeviceContainer devices;
for (uint32_t i = 1; i < nodes.GetN(); ++i) {
devices.Add(p2p.Install(nodes.Get(0), nodes.Get(i))); // Hub is node 0
}
// Install Internet stack
InternetStackHelper stack;
stack.Install(nodes);
// Assign IP addresses
Ipv4AddressHelper address;
for (uint32_t i = 0; i < devices.GetN(); i += 2) {
std::ostringstream subnet;
subnet << “192.168.” << i / 2 + 1 << “.0”;
address.SetBase(subnet.str().c_str(), “255.255.255.0”);
address.Assign(NetDeviceContainer(devices.Get(i), devices.Get(i + 1)));
}
// Set up server application
UdpEchoServerHelper echoServer(9);
ApplicationContainer serverApps = echoServer.Install(nodes.Get(0)); // Node 0 is the server
serverApps.Start(Seconds(1.0));
serverApps.Stop(Seconds(10.0));
// Set up client applications
UdpEchoClientHelper echoClient(Ipv4Address(“192.168.1.1”), 9);
echoClient.SetAttribute(“MaxPackets”, UintegerValue(5));
echoClient.SetAttribute(“Interval”, TimeValue(Seconds(1.0)));
echoClient.SetAttribute(“PacketSize”, UintegerValue(1024));
ApplicationContainer clientApps = echoClient.Install(nodes.Get(2)); // Node 2 is the client
clientApps.Start(Seconds(2.0));
clientApps.Stop(Seconds(10.0));
// Enable packet capture
p2p.EnablePcapAll(“logical-topology”);
// Run simulation
Simulator::Run();
Simulator::Destroy();
return 0;
}
- Extend the Simulation
- Add More Nodes: Maximize the volume of nodes within the topology.
- Vary Topologies: Add numerous logical topologies such as ring and mesh.
- Analyze Performance: Estimate the performance parameters like throughput, latency, and packet loss for various configurations.
Here, Logical Topology has been successfully implemented and analyzed using NS3, employing an innovative approach, with a detailed explanation to follow in the upcoming manual.