How to Begin Implement Network Layer in NS3

To implement the Network Layer in NS-3 have been involved for generate the custom routing protocol or network layer functionality which maintain the packet forwarding, routing, and addressing. The network layer has links the transport layer by the lower layers such as link and physical and assures packets are delivered with the network.

Here’s a guide to implementing the Network Layer in NS-3:

Steps to Begin Implement Network Layer in NS3

Step 1: Understand the Network Layer

1. Responsibilities:
   • Routing: Define the packets path should take to reach their destination.
   • Forwarding: Distribute the packets for next hop according to the routing table.
   • Addressing: Allocate and interpret the logical addresses for sample IP addresses.
   • Error Handling: maintain the issues such as stopped packets, TTL expiration, etc.
2. Common Implementations:
   • Custom routing protocols for instance Dijkstra-based, Bellman-Ford, AODV.
   • Improvements the existing NS-3 environments have routing protocols such as OLSR or RIP.

Step 2: Set Up NS-3

1. Install NS-3:

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 the basic sample:

./ns3 run examples/tutorial/first

Step 3: Plan the Network Layer Implementation

1. Core Components:
   • Routing Table: It manages the information about accessible destinations and next hops.
   • Packet Forwarding Logic: Define on how the packets are transmitting among the nodes.
   • Route Discovery/Update: Handle the routing bring up-to-date in dynamic networks.
2. Workflow:
   • Build a custom for routing protocol class.
   • Execute the routing table handle the packet sending.
   • Incorporate by tool NS-3’s has stacked the network.

Step 4: Implement the Network Layer

Step 4.1: Define the Routing Protocol Class

Encompass the Ipv4RoutingProtocol class for build the custom routing protocol.

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

#include “ns3/socket.h”

#include <map>

using namespace ns3;

class CustomRoutingProtocol : public Ipv4RoutingProtocol {

public:

static TypeId GetTypeId(void);

CustomRoutingProtocol();

virtual ~CustomRoutingProtocol();

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;

void AddRoute(Ipv4Address destination, Ipv4Address nextHop, uint32_t interface);

private:

struct RoutingEntry {

Ipv4Address destination;

Ipv4Address nextHop;

uint32_t interface;

};

std::map<Ipv4Address, RoutingEntry> m_routingTable; // Routing table

};

Step 4.2: Implement Core Functions

• Add Route: Improve the entries for routing table.

void CustomRoutingProtocol::AddRoute(Ipv4Address destination, Ipv4Address nextHop, uint32_t interface) {

m_routingTable[destination] = {destination, nextHop, interface};

}

• Route Output: Define the next hop for outgoing packets.

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

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

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

auto it = m_routingTable.find(header.GetDestination());

if (it != m_routingTable.end()) {

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

route->SetGateway(it->second.nextHop);

route->SetOutputDevice(GetNode()->GetDevice(it->second.interface));

return route;

}

sockerr = Socket::ERROR_NOROUTETOHOST;

return nullptr;

}

• Route Input: Maintain the incoming packets and decide whether to forward or deliver locally.

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

Ptr<const NetDevice> idev, UnicastForwardCallback ucb,

MulticastForwardCallback mcb, LocalDeliverCallback lcb,

ErrorCallback ecb) {

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

if (header.GetDestination() == myAddress) {

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

return true;

}

auto it = m_routingTable.find(header.GetDestination());

if (it != m_routingTable.end()) {

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

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

route->SetGateway(it->second.nextHop);

ucb(route, packet, header); // Forward to next hop

return true;

}

return false; // No route found

}

Step 5: Register the Protocol

Store the protocol by NS-3’s TypeId system:

TypeId CustomRoutingProtocol::GetTypeId(void) {

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

.SetParent<Ipv4RoutingProtocol>()

.SetGroupName(“Internet”)

.AddConstructor<CustomRoutingProtocol>();

return tid;

}

Step 6: Integrate into a Simulation

1. Simulation Script Example:

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

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

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

NodeContainer nodes;

nodes.Create(4);

PointToPointHelper p2p;

p2p.SetDeviceAttribute(“DataRate”, StringValue(“10Mbps”));

p2p.SetChannelAttribute(“Delay”, StringValue(“2ms”));

NetDeviceContainer devices = p2p.Install(nodes.Get(0), nodes.Get(1));

devices.Add(p2p.Install(nodes.Get(1), nodes.Get(2)));

devices.Add(p2p.Install(nodes.Get(2), nodes.Get(3)));

InternetStackHelper stack;

Ptr<CustomRoutingProtocol> customRouting = CreateObject<CustomRoutingProtocol>();

// Add static routes

customRouting->AddRoute(Ipv4Address(“10.1.1.2”), Ipv4Address(“10.1.1.1”), 0);

customRouting->AddRoute(Ipv4Address(“10.1.1.3”), Ipv4Address(“10.1.1.2”), 1);

stack.SetRoutingHelper(customRouting);

stack.Install(nodes);

Simulator::Run();

Simulator::Destroy();

return 0;

}

Step 7: Test and Debug

1. Enable Logging: Use NS-3’s logging system to debug:

export NS_LOG=”CustomRoutingProtocol=level_all|prefix_time”

./ns3 run my-simulation

1. Verify Behavior:
   • Test the routing table correctness.
   • Verify the packet sending and distribution.

Step 8: Extend and Optimize

1. Enhancements:
   • Improve the dynamic routing logic for varying the network topologies.
   • Incorporate the performance of parameter metrics such as delay, bandwidth, or hop count.
2. Performance Testing:
   • Experiment through higher networks in dynamic environment.
   • Routing effectiveness is calculating the protocol overhead.

We collective the basic to advanced information that will help you to simulate the network layer projects using ns3 simulation tool. Let me know if you required more details about this process we will offered it.