To implement a unicast routing protocol in ns-3, we create a custom routing protocol for handling the routing of packets from a single source to a single destination.
The given below steps will guide to implement the unicast routing in ns3.
Step-by-Step Implementation
- Set Up ns-3 Environment: Make sure that ns3 is installed on the system.
- Include Necessary Libraries: Include the required ns-3 libraries in your script.
- Define Network Topology: Create the nodes and links for your network topology.
- Install Internet Stack: Install the Internet stack on your nodes.
- Implement the Unicast Routing Protocol: Create a custom routing protocol class that routes packets based on unicast routing principles.
- Integrate the Custom Routing Protocol: Integrate your custom routing protocol into the ns-3 stack.
- Set Up Applications: Install applications to generate traffic and test the routing.
- Run the Simulation: Configure the simulation parameters and run it.
Example Implementation in C++
Here’s a detailed example to help you implement a unicast routing protocol in ns-3:
- Include Libraries:
#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/ipv4-routing-protocol.h”
#include “ns3/ipv4-list-routing-helper.h”
#include <map>
Define Network Topology:
using namespace ns3;
int main(int argc, char *argv[]) {
CommandLine cmd;
cmd.Parse(argc, argv);
NodeContainer nodes;
nodes.Create(4);
PointToPointHelper pointToPoint;
pointToPoint.SetDeviceAttribute(“DataRate”, StringValue(“5Mbps”));
pointToPoint.SetChannelAttribute(“Delay”, StringValue(“2ms”));
NetDeviceContainer devices01 = pointToPoint.Install(nodes.Get(0), nodes.Get(1));
NetDeviceContainer devices12 = pointToPoint.Install(nodes.Get(1), nodes.Get(2));
NetDeviceContainer devices23 = pointToPoint.Install(nodes.Get(2), nodes.Get(3));
NetDeviceContainer devices30 = pointToPoint.Install(nodes.Get(3), nodes.Get(0));
InternetStackHelper stack;
stack.Install(nodes);
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);
Implement the Unicast Routing Protocol:
- Create a new header file unicast-routing.h:
#ifndef UNICAST_ROUTING_H
#define UNICAST_ROUTING_H
#include “ns3/ipv4-routing-protocol.h”
#include “ns3/ipv4.h”
#include “ns3/net-device.h”
#include “ns3/ptr.h”
#include “ns3/socket.h”
#include <map>
#include <vector>
namespace ns3 {
class UnicastRouting : public Ipv4RoutingProtocol {
public:
static TypeId GetTypeId(void);
UnicastRouting();
virtual ~UnicastRouting();
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 Start();
private:
void ComputeRoutes();
void DistributeRoutes();
void ReceiveRoutes(Ptr<Socket> socket);
Ptr<Ipv4> m_ipv4;
std::map<Ipv4Address, Ipv4Address> m_routingTable;
std::map<uint32_t, Ptr<Socket>> m_socketMap;
Time m_updateInterval;
EventId m_updateEvent;
};
}
#endif // UNICAST_ROUTING_H
Create the corresponding implementation file unicast-routing.cc:
#include “unicast-routing.h”
#include “ns3/log.h”
#include “ns3/ipv4-routing-table-entry.h”
#include “ns3/simulator.h”
#include “ns3/inet-socket-address.h”
namespace ns3 {
NS_LOG_COMPONENT_DEFINE(“UnicastRouting”);
NS_OBJECT_ENSURE_REGISTERED(UnicastRouting);
TypeId UnicastRouting::GetTypeId(void) {
static TypeId tid = TypeId(“ns3::UnicastRouting”)
.SetParent<Ipv4RoutingProtocol>()
.SetGroupName(“Internet”)
.AddConstructor<UnicastRouting>();
return tid;
}
UnicastRouting::UnicastRouting() : m_updateInterval(Seconds(5)) {
NS_LOG_FUNCTION(this);
Simulator::Schedule(Seconds(1.0), &UnicastRouting::Start, this);
}
UnicastRouting::~UnicastRouting() {
NS_LOG_FUNCTION(this);
}
void UnicastRouting::SetIpv4(Ptr<Ipv4> ipv4) {
NS_LOG_FUNCTION(this << ipv4);
m_ipv4 = ipv4;
}
void UnicastRouting::Start() {
NS_LOG_FUNCTION(this);
ComputeRoutes();
DistributeRoutes();
m_updateEvent = Simulator::Schedule(m_updateInterval, &UnicastRouting::Start, this);
}
void UnicastRouting::ComputeRoutes() {
NS_LOG_FUNCTION(this);
// Example: static routes
m_routingTable[Ipv4Address(“10.1.1.2”)] = Ipv4Address(“10.1.2.1”);
m_routingTable[Ipv4Address(“10.1.2.2”)] = Ipv4Address(“10.1.3.1”);
m_routingTable[Ipv4Address(“10.1.3.2”)] = Ipv4Address(“10.1.4.1”);
m_routingTable[Ipv4Address(“10.1.4.2”)] = Ipv4Address(“10.1.1.1”);
}
void UnicastRouting::DistributeRoutes() {
NS_LOG_FUNCTION(this);
Ptr<Packet> packet = Create<Packet>();
for (auto const &entry : m_routingTable) {
Ipv4Header header;
header.SetSource(entry.first);
header.SetDestination(entry.second);
packet->AddHeader(header);
}
for (uint32_t i = 0; i < m_ipv4->GetNInterfaces(); ++i) {
Ptr<Socket> socket = m_socketMap[i];
socket->SendTo(packet, 0, InetSocketAddress(Ipv4Address::GetBroadcast(), 80));
}
}
void UnicastRouting::ReceiveRoutes(Ptr<Socket> socket) {
NS_LOG_FUNCTION(this);
Ptr<Packet> packet = socket->Recv();
Ipv4Header header;
packet->RemoveHeader(header);
Ipv4Address src = header.GetSource();
Ipv4Address dest = header.GetDestination();
m_routingTable[dest] = src;
}
Ptr<Ipv4Route> UnicastRouting::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();
if (m_routingTable.find(dest) == m_routingTable.end()) {
sockerr = Socket::ERROR_NOROUTETOHOST;
return 0;
}
Ptr<Ipv4Route> route = Create<Ipv4Route>();
route->SetDestination(dest);
route->SetGateway(m_routingTable[dest]);
route->SetOutputDevice(oif);
return route;
}
bool UnicastRouting::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 (dest == m_ipv4->GetAddress(1, 0).GetLocal()) {
lcb(p, header, idev);
return true;
}
if (m_routingTable.find(dest) == m_routingTable.end()) {
ecb(p, header, Socket::ERROR_NOROUTETOHOST);
return false;
}
Ptr<Ipv4Route> route = Create<Ipv4Route>();
route->SetDestination(dest);
route->SetGateway(m_routingTable[dest]);
route->SetOutputDevice(idev);
ucb(route, p, header);
return true;
}
void UnicastRouting::NotifyInterfaceUp(uint32_t interface) {
NS_LOG_FUNCTION(this << interface);
Ptr<Socket> socket = Socket::CreateSocket(GetObject<Node>(), TypeId::LookupByName(“ns3::UdpSocketFactory”));
socket->SetAllowBroadcast(true);
socket->BindToNetDevice(m_ipv4->GetNetDevice(interface));
socket->Bind(InetSocketAddress(Ipv4Address::GetAny(), 80));
socket->SetRecvCallback(MakeCallback(&UnicastRouting::ReceiveRoutes, this));
m_socketMap[interface] = socket;
}
void UnicastRouting::NotifyInterfaceDown(uint32_t interface) {
NS_LOG_FUNCTION(this << interface);
m_socketMap[interface]->Close();
m_socketMap.erase(interface);
}
void UnicastRouting::NotifyAddAddress(uint32_t interface,
Ipv4InterfaceAddress address) {
NS_LOG_FUNCTION(this << interface << address);
}
void UnicastRouting::NotifyRemoveAddress(uint32_t interface,
Ipv4InterfaceAddress address) {
NS_LOG_FUNCTION(this << interface << address);
}
}
Integrate the Custom Routing Protocol:
#include “unicast-routing.h”
int main(int argc, char *argv[]) {
CommandLine cmd;
cmd.Parse(argc, argv);
NodeContainer nodes;
nodes.Create(4);
PointToPointHelper pointToPoint;
pointToPoint.SetDeviceAttribute(“DataRate”, StringValue(“5Mbps”));
pointToPoint.SetChannelAttribute(“Delay”, StringValue(“2ms”));
NetDeviceContainer devices01 = pointToPoint.Install(nodes.Get(0), nodes.Get(1));
NetDeviceContainer devices12 = pointToPoint.Install(nodes.Get(1), nodes.Get(2));
NetDeviceContainer devices23 = pointToPoint.Install(nodes.Get(2), nodes.Get(3));
NetDeviceContainer devices30 = pointToPoint.Install(nodes.Get(3), nodes.Get(0));
InternetStackHelper stack;
UnicastRoutingHelper unicastRouting;
Ipv4ListRoutingHelper list;
list.Add(unicastRouting, 0);
stack.SetRoutingHelper(list);
stack.Install(nodes);
Ipv4AddressHelper address;
address.SetBase(“10.1.1.0”, “255.255.255.0”);
address.Assign(devices01);
address.SetBase(“10.1.2.0”, “255.255.255.0”);
address.Assign(devices12);
address.SetBase(“10.1.3.0”, “255.255.255.0”);
address.Assign(devices23);
address.SetBase(“10.1.4.0”, “255.255.255.0”);
address.Assign(devices30);
// Set up applications
uint16_t port = 9;
UdpEchoServerHelper server(port);
ApplicationContainer apps = server.Install(nodes.Get(3));
apps.Start(Seconds(1.0));
apps.Stop(Seconds(10.0));
UdpEchoClientHelper client(address.GetAddress(3), port);
client.SetAttribute(“MaxPackets”, UintegerValue(1));
client.SetAttribute(“Interval”, TimeValue(Seconds(1.0)));
client.SetAttribute(“PacketSize”, UintegerValue(1024));
apps = client.Install(nodes.Get(0));
apps.Start(Seconds(2.0));
apps.Stop(Seconds(10.0));
Simulator::Run();
Simulator::Destroy();
return 0;
}
Explanation
- Network Topology: The code sets up a network topology with four nodes connected in a ring.
- Unicast Routing Protocol: A custom unicast routing protocol class (UnicastRouting) is implemented. This class handles route computation and distribution based on unicast routing principles.
- Route Computation: The ComputeRoutes method computes static routes for the network.
- Route Distribution: The DistributeRoutes method broadcasts the computed routes to all nodes in the network.
- Route Input and Output: The RouteInput and RouteOutput methods handle packet routing based on the routing table.
- Integrate Custom Routing Protocol: The custom routing protocol is integrated into the ns-3 stack using the UnicastRoutingHelper.
- Applications: UdpEchoServer and UdpEchoClient applications are set up to test the routing.
Running the Code
- Save your script to a file, for example, unicast-routing.cc.
- Compile the script using the ns-3 build system
./waf configure –enable-examples
./waf build
./waf –run scratch/unicast-routing
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