How to Begin Implement IPv4 Protocols in NS3

To implement an IPv4 protocol within NS3, we can make or alter an Ipv4RoutingProtocol for describing the custom routing or packet-handling behavior in IPv4 networks. We follow these structured steps to get started:

Steps to Begin Implement IPv4 Protocols in NS3

Step 1: Understand NS3’s IPv4 Architecture

1. Core Components:
   • Ipv4RoutingProtocol: It is a base class in NS3 for routing protocols.
   • Ipv4: Manages IP layer operations like transmitting and packet distribution.
   • Ipv4Address and Ipv4Header: It denotes an IP addresses and packet headers.
   • Existing Routing Protocols: Examples contain AODV, OLSR, and StaticRouting are executed in the src/internet-routing component.
2. Packet Flow:
   • Once a packet reaches at a node then the routing protocol finds their next hop.
   • The protocol chooses whether transmitting the packet, locally distributing it, or losing it.

Step 2: Set Up NS3

1. Install NS3:
   • Clone and develop the NS3 environment:

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

cd ns-3-dev

./ns3 configure –enable-examples –enable-tests

./ns3 build

1. Verify Installation: Execute a sample script for verifying the correct installation:

./ns3 run examples/tutorial/first

Step 3: Plan the IPv4 Protocol

1. Define Protocol Objectives:
   • Describe the protocol goals like it a distance-vector, link-state, or hybrid protocol.
   • Routing parameters such as hop count, bandwidth, latency.
2. Identify Key Features:
   • Packet forwarding decisions.
   • Route discovery and maintenance.
   • To manage certain scenarios such as link failures.

Step 4: Implement the IPv4 Protocol

Step 4.1: Create a New Protocol Class

Make a protocol class to prolong the Ipv4RoutingProtocol class:

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

#include “ns3/node.h”

#include “ns3/socket.h”

using namespace ns3;

class MyIpv4Protocol : public Ipv4RoutingProtocol {

public:

static TypeId GetTypeId(void);

MyIpv4Protocol();

virtual ~MyIpv4Protocol();

// Required overrides

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

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

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

Ptr<const NetDevice> idev, UnicastForwardCallback ucb,

MulticastForwardCallback mcb, LocalDeliverCallback lcb,

ErrorCallback ecb) override;

virtual void NotifyInterfaceUp(uint32_t interface) override;

virtual void NotifyInterfaceDown(uint32_t interface) override;

virtual void NotifyAddAddress(uint32_t interface, Ipv4InterfaceAddress address) override;

virtual void NotifyRemoveAddress(uint32_t interface, Ipv4InterfaceAddress address) override;

private:

void UpdateRoutingTable();

void HandleIncomingPacket(Ptr<Packet> packet, const Ipv4Header &header);

};

Step 4.2: Implement Protocol Logic

• Routing Output (Forwarding Decisions): Describe how outgoing packets are sent.

Ptr<Ipv4Route> MyIpv4Protocol::RouteOutput(Ptr<Packet> packet, const Ipv4Header &header,

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

// Lookup or compute the route for the packet

Ptr<Ipv4Route> route = Create<Ipv4Route>();

route->SetDestination(header.GetDestination());

route->SetSource(Ipv4Address(“10.1.1.1”));

route->SetGateway(Ipv4Address(“10.1.1.2”));

route->SetOutputDevice(oif);

return route;

}

• Routing Input (Incoming Packets): Manage the incoming packets and choose whether transmitting, distributing, or losing them.

bool MyIpv4Protocol::RouteInput(Ptr<const Packet> packet, const Ipv4Header &header,

Ptr<const NetDevice> idev, UnicastForwardCallback ucb,

MulticastForwardCallback mcb, LocalDeliverCallback lcb,

ErrorCallback ecb) {

// Check if the packet is for this node

if (header.GetDestination() == Ipv4Address(“10.1.1.1”)) {

lcb(packet, header, idev); // Deliver locally

return true;

}

// Forward the packet

Ptr<Ipv4Route> route = LookupRoute(header.GetDestination());

if (route) {

ucb(route, packet, header);

return true;

}

ecb(packet, header, Socket::ERROR_NOROUTETOHOST);

return false;

}

• Route Maintenance:
  • Modernize routing tables at events such as interface modifications or new address tasks.

void MyIpv4Protocol::NotifyInterfaceUp(uint32_t interface) {

// Update routing table for the new interface

}

void MyIpv4Protocol::NotifyAddAddress(uint32_t interface, Ipv4InterfaceAddress address) {

// Add the address to the routing table

}

Step 5: Integrate the Protocol

Step 5.1: Register the Protocol

Record the IPV4 protocol including TypeId system of NS3:

TypeId MyIpv4Protocol::GetTypeId(void) {

static TypeId tid = TypeId(“ns3::MyIpv4Protocol”)

.SetParent<Ipv4RoutingProtocol>()

.SetGroupName(“Internet”)

.AddConstructor<MyIpv4Protocol>();

return tid;

}

Step 5.2: Add to Nodes

Incorporate the protocol to nodes utilising InternetStackHelper:

#include “ns3/internet-stack-helper.h”

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

NodeContainer nodes;

nodes.Create(3);

InternetStackHelper stack;

Ptr<MyIpv4Protocol> myRouting = CreateObject<MyIpv4Protocol>();

stack.SetRoutingHelper(myRouting);  // Use your custom protocol

stack.Install(nodes);

Simulator::Run();

Simulator::Destroy();

return 0;

}

Step 6: Test and Debug

1. Simulation Setup:
   • Make a simple topology using PointToPointHelper or CsmaHelper.
   • Set up traffic sources like OnOffApplication.
2. Enable Logging:

export NS_LOG=”MyIpv4Protocol=level_all|prefix_time”

./ns3 run my-simulation

1. Analyze Results:
   • Authenticate the behaviour of routing using FlowMonitor or packet tracing (PcapHelper).

Step 7: Optimize and Extend

1. Performance:
   • Enhance the route lookup mechanisms for large networks.
   • Execute caching for reiterated route demands.
2. Extensions:
   • Integrate advanced aspects such as dynamic routing, QoS support, or load balancing.
   • Add mobility patterns for analysing the dynamic scenarios.

As indicated above procedure, we can acquire detailed knowledge on how to implement and enhance the IPv4 Protocols using NS3 environment.  Additional information with certain details on this topic will be shared in upcoming manual.