How to Begin Implement a Next Hop Protocol in NS3

To stimulate a Next-Hop Protocols are routing devices in which the routing decision is create according to the next-hop neighbor for sending the packet closer to the destination. Executing the Next-Hop Protocol in ns3 includes building a custom routing protocol which uses a basic metrics like as hop count, geographic distance, or link quality to determine the next hop for packet forwarding.

Here’s how to implement a Next-Hop Protocol in ns-3:

Steps to Begin Implement a Next Hop Protocol in NS3

1. Understand Next-Hop Protocols

• Key Features:
  • Define for improve a next-hop neighbor in sending a packet.
  • Metrics could contain:
    • Hop Count: The minimum number of hops for the destination in hop count.
    • Geographic Distance: The geographic distance for sending the node near to the destination.
    • Link Quality: Select the neighbours by higher signal strength.
• Simulation Goals:
  • Estimate the protocol performance according to the delivery ratio, latency, and routing overhead.

2. Set up ns-3 Environment

1. Install ns3:

git clone https://gitlab.com/nsnam/ns-3-dev.git

cd ns-3-dev

./build.py

1. Validate the installation:

./ns3 run hello-simulator

3. Plan the Network Topology

• Components:
  • The network topology has includes the mobile or fixed nodes by connectivity.
  • The components are traffic sources and destinations.
• Topology:
  • Nodes are organized in the grid or arbitrarily placed.

4. Implement the Next-Hop Protocol
5. Define the Protocol Class

1. Build a new class inheriting from Ipv4RoutingProtocol:

#include “ns3/ipv4-routing-protocol.h”

#include “ns3/ipv4-route.h”

#include “ns3/mobility-module.h”

#include “ns3/simulator.h”

class NextHopRouting : public ns3::Ipv4RoutingProtocol {

public:

NextHopRouting();

virtual ~NextHopRouting();

Ptr<Ipv4Route> RouteOutput(Ptr<Packet> packet, const Ipv4Header &header,

Ptr<NetDevice> oif, Socket::SocketErrno &sockerr) override;

bool RouteInput(Ptr<const Packet> packet, const Ipv4Header &header,

Ptr<const NetDevice> idev, UnicastForwardCallback ucb,

MulticastForwardCallback mcb, LocalDeliverCallback lcb,

ErrorCallback ecb) override;

void UpdateNeighborTable();

Ptr<Ipv4Route> SelectNextHop(ns3::Ipv4Address dest);

private:

std::map<ns3::Ipv4Address, ns3::Vector> m_neighborTable;  // Neighbor table

};

1. Neighbor Table Maintenance:
   • 1. Periodically broadcast for HELLO packets in neighbours.
   • It handles the table for neighbours’ addresses and metrics for sample position or link quality.
2. Next-Hop Selection:
   • Use metrics for establish the improved neighbor for sending a packet.
   • For sample, choose the neighbor by the lowest hop count or the closest geographic distance.

1. Create a Helper Class

1. Define the Helper:

class NextHopHelper : public ns3::Ipv4RoutingHelper {

public:

NextHopHelper() {}

Ptr<Ipv4RoutingProtocol> Create(Ptr<Node> node) const override {

return CreateObject<NextHopRouting>();

}

};

1. Integrate into Simulation Script:

NextHopHelper nextHopHelper;

ns3::InternetStackHelper stack;

stack.SetRoutingHelper(nextHopHelper);

stack.Install(nodes);

5. Set Up the Simulation
6. Define Nodes

ns3::NodeContainer nodes;

nodes.Create(10);  // Create 10 nodes

1. Set Up Mobility

1. Random Placement:

ns3::MobilityHelper mobility;

mobility.SetPositionAllocator(“ns3::RandomRectanglePositionAllocator”,

“X”, ns3::StringValue(“ns3::UniformRandomVariable[Min=0.0|Max=100.0]”),

“Y”, ns3::StringValue(“ns3::UniformRandomVariable[Min=0.0|Max=100.0]”));

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

mobility.Install(nodes);

1. Grid Placement (Optional):

ns3::MobilityHelper mobility;

mobility.SetPositionAllocator(“ns3::GridPositionAllocator”,

“MinX”, ns3::DoubleValue(0.0),

“MinY”, ns3::DoubleValue(0.0),

“DeltaX”, ns3::DoubleValue(20.0),

“DeltaY”, ns3::DoubleValue(20.0),

“GridWidth”, ns3::UintegerValue(5),

“LayoutType”, ns3::StringValue(“RowFirst”));

mobility.Install(nodes);

1. Set Up Wireless Communication

ns3::WifiHelper wifi;

wifi.SetStandard(ns3::WIFI_PHY_STANDARD_80211);

ns3::WifiMacHelper mac;

mac.SetType(“ns3::AdhocWifiMac”);

ns3::WifiPhyHelper phy = ns3::WifiPhyHelper::Default();

phy.SetChannel(ns3::YansWifiChannelHelper::Default().Create());

ns3::NetDeviceContainer devices = wifi.Install(phy, mac, nodes);

1. Assign IP Addresses

ns3::Ipv4AddressHelper address;

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

ns3::Ipv4InterfaceContainer interfaces = address.Assign(devices);

6. Generate Traffic

UDP Traffic

// UDP Echo server on Node 9

ns3::UdpEchoServerHelper echoServer(9);

ns3::ApplicationContainer serverApp = echoServer.Install(nodes.Get(9));

serverApp.Start(ns3::Seconds(1.0));

serverApp.Stop(ns3::Seconds(20.0));

// UDP Echo client on Node 0

ns3::UdpEchoClientHelper echoClient(interfaces.GetAddress(9), 9);

echoClient.SetAttribute(“MaxPackets”, ns3::UintegerValue(10));

echoClient.SetAttribute(“Interval”, ns3::TimeValue(ns3::Seconds(1.0)));

echoClient.SetAttribute(“PacketSize”, ns3::UintegerValue(512));

ns3::ApplicationContainer clientApp = echoClient.Install(nodes.Get(0));

clientApp.Start(ns3::Seconds(2.0));

clientApp.Stop(ns3::Seconds(20.0));

7. Run the Simulation

ns3::Simulator::Run();

ns3::Simulator::Destroy();

8. Analyze Results

Metrics:

• Packet Delivery Ratio (PDR):
  • Calculate the PDR ratio for successfully delivered the packets.
• Latency:
  • Estimate the average delay for packet delivery.
• Routing Overhead:
  • Exchanged the Total the number of control messages.

Tracing and Visualization:

• Ensure the .pcap tracing for packet examine:

ns3::AsciiTraceHelper ascii;

phy.EnableAsciiAll(ascii.CreateFileStream(“next-hop.tr”));

phy.EnablePcapAll(“next-hop”);

• Use the envision for NetAnim:

./waf –run “next-hop-simulation –vis”

9. Iterate and Enhance

• Advanced Features:
  • Execute the advanced parameter metrics for select the next-hop for instance energy-aware routing.
  • It replicate the mobility and connection failures for validate the robustness.
• Protocol Comparison:
  • It associates the next-hop protocol by AODV, DSDV, or other routing protocols.
• Optimization:
  • It enhances the neighbor discovery and decrease the routing overhead.

In this manual, we clearly explained the concepts about how to simulate and install the environment for Next Hop routing protocol projects in ns3 tool and also we offered the simulation procedures, sample snippets and the extension for this project with the project ideas. If you need to know more details feel free to ask!