To implement a custom Network Layer in ns3, we have to create new classes which simulates network layer’s behavior and functionalities, that include packet forwarding, routing, and addressing.
Below is the complete guide to create a basic custom Network Layer in ns3.
Step-by-step guide on implementing network layer in ns3
- Set up your ns3 :
- Make sure that ns3 is installed in the computer. If not, install it.
- Create a New Module for network layer:
- Go to the src directory in ns3 and create a new directory named custom-network-layer. Create subdirectories named model, helper, and examples, inside the src directory.
- Define the network layer protocol:
- Create .cc and .h files for the network layer protocol in the model directory. Define the CustomRoutingProtocol and CustomIpv4 that simulates the behavior of network layer.
- Implement the network layer class:
- Implement the key components of network layer such as packet forwarding, routing decisions, and addressing. For the routing protocol and IP forwarding that interact with the network layer, create classes.
- Integrate the network layer with ns3 network system:
- Modify the Ipv4 class or create a custom Ipv4 device that can handle network layer logic. Register network layer as a protocol in ns3.
- Create simulation script:
- Set up a network topology.
- Install the Internet stack.
- Use the network layer helper to enable network layer.
- Set up applications and run the simulation.
Example Code Structure
Below is the example for the implementation of custom network layer in ns3.
Define custom network layer Protocol
// src/custom-network-layer/model/custom-routing-protocol.h
#ifndef CUSTOM_ROUTING_PROTOCOL_H
#define CUSTOM_ROUTING_PROTOCOL_H
#include “ns3/ipv4-routing-protocol.h”
#include “ns3/ipv4.h”
#include “ns3/ipv4-l3-protocol.h”
#include “ns3/ipv4-route.h”
#include “ns3/node.h”
#include “ns3/net-device.h”
#include “ns3/socket.h”
#include “ns3/timer.h”
#include <vector>
#include <map>
namespace ns3 {
class CustomRoutingProtocol : public Ipv4RoutingProtocol
{
public:
static TypeId GetTypeId (void);
CustomRoutingProtocol ();
virtual ~CustomRoutingProtocol ();
// Inherited from Ipv4RoutingProtocol
virtual Ptr<Ipv4Route> RouteOutput (Ptr<Packet> p, const Ipv4Header &header,
Ptr<NetDevice> oif, Socket::SocketErrno &sockerr);
virtual bool RouteInput (Ptr<const Packet> p, const Ipv4Header &header, Ptr<const NetDevice> idev,
UnicastForwardCallback ucb, MulticastForwardCallback mcb,
LocalDeliverCallback lcb, ErrorCallback ecb);
virtual void NotifyInterfaceUp (uint32_t interface);
virtual void NotifyInterfaceDown (uint32_t interface);
virtual void NotifyAddAddress (uint32_t interface, Ipv4InterfaceAddress address);
virtual void NotifyRemoveAddress (uint32_t interface, Ipv4InterfaceAddress address);
virtual void SetIpv4 (Ptr<Ipv4> ipv4);
void RecvCustomRoutingProtocol (Ptr<Socket> socket);
private:
void Start ();
void Stop ();
void SendPacket ();
void HandlePacket (Ptr<Packet> packet);
Ptr<Ipv4> m_ipv4;
std::map<Ptr<Socket>, Ipv4InterfaceAddress> m_socketAddresses;
std::map<Ipv4Address, Ptr<Ipv4Route>> m_routes;
Timer m_timer;
};
} // namespace ns3
#endif // CUSTOM_ROUTING_PROTOCOL_H
Implement Custom Network Layer Classes
// src/custom-network-layer/model/custom-routing-protocol.cc
#include “custom-routing-protocol.h”
#include “ns3/log.h”
#include “ns3/ipv4-static-routing.h”
#include “ns3/ipv4-static-routing-helper.h”
namespace ns3 {
NS_LOG_COMPONENT_DEFINE (“CustomRoutingProtocol”);
NS_OBJECT_ENSURE_REGISTERED (CustomRoutingProtocol);
TypeId
CustomRoutingProtocol::GetTypeId (void)
{
static TypeId tid = TypeId (“ns3::CustomRoutingProtocol”)
.SetParent<Ipv4RoutingProtocol> ()
.SetGroupName (“Internet”)
.AddConstructor<CustomRoutingProtocol> ();
return tid;
}
CustomRoutingProtocol::CustomRoutingProtocol ()
{
NS_LOG_FUNCTION (this);
}
CustomRoutingProtocol::~CustomRoutingProtocol ()
{
NS_LOG_FUNCTION (this);
}
void
CustomRoutingProtocol::SetIpv4 (Ptr<Ipv4> ipv4)
{
NS_LOG_FUNCTION (this << ipv4);
m_ipv4 = ipv4;
Start ();
}
void
CustomRoutingProtocol::NotifyInterfaceUp (uint32_t interface)
{
NS_LOG_FUNCTION (this << interface);
}
void
CustomRoutingProtocol::NotifyInterfaceDown (uint32_t interface)
{
NS_LOG_FUNCTION (this << interface);
}
void
CustomRoutingProtocol::NotifyAddAddress (uint32_t interface, Ipv4InterfaceAddress address)
{
NS_LOG_FUNCTION (this << interface << address);
}
void
CustomRoutingProtocol::NotifyRemoveAddress (uint32_t interface, Ipv4InterfaceAddress address)
{
NS_LOG_FUNCTION (this << interface << address);
}
void
CustomRoutingProtocol::Start ()
{
NS_LOG_FUNCTION (this);
}
void
CustomRoutingProtocol::Stop ()
{
NS_LOG_FUNCTION (this);
}
void
CustomRoutingProtocol::SendPacket ()
{
NS_LOG_FUNCTION (this);
// Implement the logic to send a packet
}
void
CustomRoutingProtocol::HandlePacket (Ptr<Packet> packet)
{
NS_LOG_FUNCTION (this << packet);
// Implement the logic to handle a received packet
}
Ptr<Ipv4Route>
CustomRoutingProtocol::RouteOutput (Ptr<Packet> p, const Ipv4Header &header,
Ptr<NetDevice> oif, Socket::SocketErrno &sockerr)
{
NS_LOG_FUNCTION (this << p << header << oif << sockerr);
Ipv4Address dest = header.GetDestination ();
Ptr<Ipv4Route> route = Create<Ipv4Route> ();
if (m_routes.find (dest) != m_routes.end ())
{
route->SetDestination (dest);
route->SetOutputDevice (oif);
route->SetGateway (m_routes[dest]->GetGateway ());
return route;
}
else
{
sockerr = Socket::ERROR_NOROUTETOHOST;
return nullptr;
}
}
bool
CustomRoutingProtocol::RouteInput (Ptr<const Packet> p, const Ipv4Header &header, Ptr<const NetDevice> idev,
UnicastForwardCallback ucb, MulticastForwardCallback mcb,
LocalDeliverCallback lcb, ErrorCallback ecb)
{
NS_LOG_FUNCTION (this << p << header << idev << ucb << mcb << lcb << ecb);
Ipv4Address dest = header.GetDestination ();
if (m_routes.find (dest) != m_routes.end ())
{
Ptr<Ipv4Route> route = Create<Ipv4Route> ();
route->SetDestination (dest);
route->SetOutputDevice (m_ipv4->GetNetDevice (0)); // Example output device
route->SetGateway (m_routes[dest]->GetGateway ());
ucb (route, p, header);
return true;
}
else
{
return false;
}
}
void
CustomRoutingProtocol::RecvCustomRoutingProtocol (Ptr<Socket> socket)
{
NS_LOG_FUNCTION (this << socket);
Ptr<Packet> packet = socket->Recv ();
Ipv4Header ipv4Header;
packet->RemoveHeader (ipv4Header);
Ipv4Address src = ipv4Header.GetSource ();
Ipv4Address dst = ipv4Header.GetDestination ();
// Process the packet
HandlePacket (packet);
}
} // namespace ns3
Define Custom Helper
// src/custom-network-layer/helper/custom-network-layer-helper.h
#ifndef CUSTOM_NETWORK_LAYER_HELPER_H
#define CUSTOM_NETWORK_LAYER_HELPER_H
#include “ns3/ipv4-routing-helper.h”
#include “ns3/object-factory.h”
#include “ns3/custom-routing-protocol.h”
namespace ns3 {
class CustomNetworkLayerHelper : public Ipv4RoutingHelper
{
public:
CustomNetworkLayerHelper ();
CustomNetworkLayerHelper (const CustomNetworkLayerHelper &);
CustomNetworkLayerHelper &operator= (const CustomNetworkLayerHelper &);
virtual ~CustomNetworkLayerHelper ();
virtual CustomNetworkLayerHelper* Copy (void) const;
virtual Ptr<Ipv4RoutingProtocol> Create (Ptr<Node> node) const;
};
} // namespace ns3
#endif // CUSTOM_NETWORK_LAYER_HELPER_H
Implement Custom Helper
// src/custom-network-layer/helper/custom-network-layer-helper.cc
#include “custom-network-layer-helper.h”
#include “ns3/custom-routing-protocol.h”
#include “ns3/node.h”
namespace ns3 {
CustomNetworkLayerHelper::CustomNetworkLayerHelper ()
{
m_factory.SetTypeId (CustomRoutingProtocol::GetTypeId ());
}
CustomNetworkLayerHelper::CustomNetworkLayerHelper (const CustomNetworkLayerHelper &o)
{
}
CustomNetworkLayerHelper&
CustomNetworkLayerHelper::operator= (const CustomNetworkLayerHelper &o)
{
return *this;
}
CustomNetworkLayerHelper::~CustomNetworkLayerHelper ()
{
}
CustomNetworkLayerHelper*
CustomNetworkLayerHelper::Copy (void) const
{
return new CustomNetworkLayerHelper (*this);
}
Ptr<Ipv4RoutingProtocol>
CustomNetworkLayerHelper::Create (Ptr<Node> node) const
{
Ptr<CustomRoutingProtocol> protocol = m_factory.Create<CustomRoutingProtocol> ();
node->AggregateObject (protocol);
return protocol;
}
} // namespace ns3
Example Simulation Script
// examples/custom-network-layer-simulation.cc
#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”
#include “ns3/custom-network-layer-helper.h”
using namespace ns3;
NS_LOG_COMPONENT_DEFINE (“CustomNetworkLayerSimulation”);
int main (int argc, char *argv[])
{
CommandLine cmd;
cmd.Parse (argc, argv);
// Create nodes
NodeContainer nodes;
nodes.Create (4);
// Create point-to-point links
PointToPointHelper p2p;
p2p.SetDeviceAttribute (“DataRate”, StringValue (“1Gbps”));
p2p.SetChannelAttribute (“Delay”, StringValue (“2ms”));
NetDeviceContainer devices01 = p2p.Install (nodes.Get (0), nodes.Get (1));
NetDeviceContainer devices12 = p2p.Install (nodes.Get (1), nodes.Get (2));
NetDeviceContainer devices23 = p2p.Install (nodes.Get (2), nodes.Get (3));
NetDeviceContainer devices30 = p2p.Install (nodes.Get (3), nodes.Get (0));
// Install Custom Network Layer on all nodes
CustomNetworkLayerHelper customNetworkLayer;
InternetStackHelper internet;
internet.SetRoutingHelper (customNetworkLayer);
internet.Install (nodes);
// Assign IP addresses
Ipv4AddressHelper address;
address.SetBase (“10.1.1.0”, “255.255.255.0”);
Ipv4InterfaceContainer interfaces01 = address.Assign (devices01);
address.SetBase (“10.1.2.0”, “255.255.255.0”);
Ipv4InterfaceContainer interfaces12 = address.Assign (devices12);
address.SetBase (“10.1.3.0”, “255.255.255.0”);
Ipv4InterfaceContainer interfaces23 = address.Assign (devices23);
address.SetBase (“10.1.4.0”, “255.255.255.0”);
Ipv4InterfaceContainer interfaces30 = address.Assign (devices30);
// Create a packet sink to receive packets
uint16_t sinkPort = 8080;
Address sinkAddress (InetSocketAddress (Ipv4Address (“10.1.1.1”), sinkPort));
PacketSinkHelper packetSinkHelper (“ns3::TcpSocketFactory”, sinkAddress);
ApplicationContainer sinkApps = packetSinkHelper.Install (nodes.Get (0));
sinkApps.Start (Seconds (1.0));
sinkApps.Stop (Seconds (10.0));
// Create a TCP client to send packets
OnOffHelper clientHelper (“ns3::TcpSocketFactory”, sinkAddress);
clientHelper.SetAttribute (“OnTime”, StringValue (“ns3::ConstantRandomVariable[Constant=1]”));
clientHelper.SetAttribute (“OffTime”, StringValue (“ns3::ConstantRandomVariable[Constant=0]”));
clientHelper.SetAttribute (“DataRate”, DataRateValue (DataRate (“1Mbps”)));
clientHelper.SetAttribute (“PacketSize”, UintegerValue (1024));
ApplicationContainer clientApps = clientHelper.Install (nodes.Get (1));
clientApps.Start (Seconds (2.0));
clientApps.Stop (Seconds (10.0));
// Enable tracing
AsciiTraceHelper ascii;
p2p.EnableAsciiAll (ascii.CreateFileStream (“custom-network-layer.tr”));
p2p.EnablePcapAll (“custom-network-layer”);
// Run the simulation
Simulator::Run ();
Simulator::Destroy ();
return 0;
}
Running the Simulation
To run the simulation, compile the script and execute it:
./waf configure –enable-examples
./waf build
./waf –run custom-network-layer-simulation
Overall, we had successfully implemented a custom Network Layer in ns3 by creating new classes that simulate the behavior of network layer functionalities, such as packet forwarding, routing, and addressing.
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