How to Start Next Hop Protocol Projects Using NS3

To start a Next-Hop Routing Protocol in NS3 simulation tool, that contains to set up nodes to forward packets according to the adjacent or next hop over a path to the destination. A “Next-Hop” protocol is generally utilised within wireless networks in which nodes only require to understand the next hop to route packets, to create it that is appropriate for dynamic and distributed environments such as MANETs (Mobile Ad hoc Networks).

Although NS3 does not natively support a built-in “Next-Hop Protocol,” we can be estimated it by executing custom logic for next-hop forwarding or by changing existing routing protocols, replicating a next-hop method.

Step-by-Step Guide to Simulate a Next-Hop Routing Protocol

  1. In an ad hoc network, we make nodes where each node sends packets to their next hop to the destination.
  2. Find the next hop according to the proximity or predefined paths to utilise custom logic or change an existing protocol like static routing.
  3. Experiment and envision the routing behavior, making sure that packets are sent via the proper next hops.

Step 1: Create a New Script for Next-Hop Routing

In the NS3’s scratch directory, we can save the below code like next_hop_simulation.cc. This instance estimates the next-hop routing by means of setting up each node depends on the nearby neighbor within the direction of the destination to send packets.

Example Code for next_hop_simulation.cc

#include “ns3/core-module.h”

#include “ns3/network-module.h”

#include “ns3/internet-module.h”

#include “ns3/mobility-module.h”

#include “ns3/wifi-module.h”

#include “ns3/applications-module.h”

#include <cmath>

using namespace ns3;

NS_LOG_COMPONENT_DEFINE(“NextHopSimulation”);

double CalculateDistance(Ptr<Node> node1, Ptr<Node> node2) {

Ptr<MobilityModel> mobility1 = node1->GetObject<MobilityModel>();

Ptr<MobilityModel> mobility2 = node2->GetObject<MobilityModel>();

return mobility1->GetDistanceFrom(mobility2);

}

void SendPacketToNextHop(Ptr<Node> source, Ptr<Node> destination, Ipv4Address destAddress, Ipv4Address nextHopAddress) {

NS_LOG_INFO(“Node ” << source->GetId() << ” forwards packet to next hop: Node with IP ” << nextHopAddress << ” towards destination Node ” << destination->GetId());

// Here we would send the packet using the NS-3 packet handling

}

void ForwardPacket(Ptr<Node> source, Ptr<Node> destination) {

Ptr<Node> bestNextHop = source;

double bestDistance = CalculateDistance(source, destination);

for (uint32_t i = 0; i < source->GetNDevices(); ++i) {

Ptr<NetDevice> device = source->GetDevice(i);

Ptr<Channel> channel = device->GetChannel();

for (uint32_t j = 0; j < channel->GetNDevices(); ++j) {

Ptr<Node> neighbor = channel->GetDevice(j)->GetNode();

if (neighbor == source) continue;

double distance = CalculateDistance(neighbor, destination);

if (distance < bestDistance) {

bestNextHop = neighbor;

bestDistance = distance;

}

}

}

if (bestNextHop != source) {

Ipv4Address nextHopAddress = bestNextHop->GetObject<Ipv4>()->GetAddress(1, 0).GetLocal();

Ipv4Address destAddress = destination->GetObject<Ipv4>()->GetAddress(1, 0).GetLocal();

SendPacketToNextHop(source, destination, destAddress, nextHopAddress);

}

}

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

LogComponentEnable(“NextHopSimulation”, LOG_LEVEL_INFO);

// Create nodes in an ad hoc network

NodeContainer nodes;

nodes.Create(5); // Example with 5 nodes

// Set up mobility model for nodes

MobilityHelper mobility;

mobility.SetPositionAllocator(“ns3::GridPositionAllocator”,

“MinX”, DoubleValue(0.0),

“MinY”, DoubleValue(0.0),

“DeltaX”, DoubleValue(50.0),

“DeltaY”, DoubleValue(50.0),

“GridWidth”, UintegerValue(3),

“LayoutType”, StringValue(“RowFirst”));

mobility.SetMobilityModel(“ns3::ConstantPositionMobilityModel”);

mobility.Install(nodes);

// Set up WiFi for ad hoc communication

WifiHelper wifi;

wifi.SetStandard(WIFI_STANDARD_80211b);

YansWifiPhyHelper wifiPhy = YansWifiPhyHelper::Default();

YansWifiChannelHelper wifiChannel = YansWifiChannelHelper::Default();

wifiPhy.SetChannel(wifiChannel.Create());

WifiMacHelper wifiMac;

wifiMac.SetType(“ns3::AdhocWifiMac”);

NetDeviceContainer devices = wifi.Install(wifiPhy, wifiMac, nodes);

// Install the Internet stack

InternetStackHelper internet;

internet.Install(nodes);

// Assign IP addresses

Ipv4AddressHelper ipv4;

ipv4.SetBase(“10.1.1.0”, “255.255.255.0”);

Ipv4InterfaceContainer interfaces = ipv4.Assign(devices);

// Schedule packet forwarding from Node 0 to Node 4

Simulator::Schedule(Seconds(1.0), &ForwardPacket, nodes.Get(0), nodes.Get(4));

 

Simulator::Run();

Simulator::Destroy();

return 0;

}

Explanation of the Code

  • Calculate Distance:
    • The CalculateDistance function calculates the Euclidean distance rely on its locations among two nodes. It is necessary, within the direction of the destination for discovering the nearest (next-hop) node.
  • Next-Hop Forwarding Logic:
    • The ForwardPacket function finds the optimal next-hop neighbor, sending a packet to the destination. It executes this by determining the closest to the destination.
    • SendPacketToNextHop records the transmitting packet to the next hop within a more comprehensive execution; this function should be managed the packet transmission.
  • Ad Hoc Network Configuration:
    • Configure five nodes including constant positions and spread out evenly across the grid.
    • In ad hoc mode WiFi is set up, permitting direct interaction among nearby nodes.
  • Packet Forwarding Simulation:
    • At 1 second, a packet is forwarded from Node 0 to Node 4 using the next-hop forwarding approach.

Step 2: Build and Run the Simulation

  1. In the scratch directory, we can save next_hop_simulation.cc.
  2. Go to a terminal, pass through to NS3 directory, and then make the script:

./ns3 build

  1. Run the simulation:

./ns3 run scratch/next_hop_simulation

Above code will run the simulation, for the next-hop routing process to indicate log messages as packets are sent to the destination.

Further Experimentation Ideas

To discover further next-hop routing behavior, we can deliberate:

  • Mobility Models: Experiment next-hop routing within a dynamic network using RandomWaypointMobilityModel or other mobility models in which nodes are travelling constantly.
  • Implementing Full Packet Forwarding Logic: Prolong SendPacketToNextHop to make and transmit real packets among the nodes.
  • Increase Network Size and Density: Make a larger ad hoc network, append additional nodes and then monitor how next-hop routing achieves scalability.
  • Implement Link Quality-based Next-Hop Selection: We need to change the ForwardPacket function, selecting the next hop not only relies on distance however also on factors such as link quality.

This resource offers a complete approach for simulating and configuring Next Hop protocol projects using NS3 simulation tool. If you have any doubt on this project, we will also clarify it.

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