How to Implement ECMP in ns3

To implement the Equal-Cost Multi-Path (ECMP) in ns3, we used this protocol for distribute traffic for the same cost across multiple paths. By simulating the ECMP in ns3 updated the routing tables to maintain multiple next-hops for the same destination.

Here are the procedures on implement the ECMP in ns3:

Steps to Implement ECMP in ns3

1. Set Up Your ns3 Workspace: To make sure ns3 is installed in the computer and configure with working directory.
2. Create a Simulation Script:
   • Describe the network topology.
   • Download the Internet stack.
   • Manually setup the routing tables to support ECMP.
   • Configure applications and execute the simulation.

Example Simulation Script

Below is the sample configuration to implement the ECMP in ns3:

#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-static-routing-helper.h”

using namespace ns3;

NS_LOG_COMPONENT_DEFINE (“EcmpExample”);

void AddEcmpRoutes (Ptr<Node> node, Ipv4Address dest, Ipv4Mask mask, std::vector<Ipv4Address> nextHops)

{

Ptr<Ipv4> ipv4 = node->GetObject<Ipv4> ();

Ptr<Ipv4StaticRouting> staticRouting = Ipv4RoutingHelper::GetStaticRouting (ipv4);

for (Ipv4Address nextHop : nextHops)

{

staticRouting->AddNetworkRouteTo (dest, mask, nextHop, 1); // Assuming all interfaces are 1

}

}

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 (“1Mbps”));

p2p.SetChannelAttribute (“Delay”, StringValue (“10ms”));

NetDeviceContainer devices01 = p2p.Install (nodes.Get (0), nodes.Get (1));

NetDeviceContainer devices02 = p2p.Install (nodes.Get (0), nodes.Get (2));

NetDeviceContainer devices13 = p2p.Install (nodes.Get (1), nodes.Get (3));

NetDeviceContainer devices23 = p2p.Install (nodes.Get (2), nodes.Get (3));

// Install the Internet stack

InternetStackHelper stack;

stack.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 interfaces02 = address.Assign (devices02);

address.SetBase (“10.1.3.0”, “255.255.255.0”);

Ipv4InterfaceContainer interfaces13 = address.Assign (devices13);

address.SetBase (“10.1.4.0”, “255.255.255.0”);

Ipv4InterfaceContainer interfaces23 = address.Assign (devices23);

// Enable ECMP by adding multiple routes

AddEcmpRoutes (nodes.Get (0), Ipv4Address (“10.1.3.0”), Ipv4Mask (“255.255.255.0”), {Ipv4Address (“10.1.1.2”), Ipv4Address (“10.1.2.2”)});

// Create a packet sink to receive packets

uint16_t sinkPort = 8080;

Address sinkAddress (InetSocketAddress (Ipv4Address (“10.1.4.1”), sinkPort));

PacketSinkHelper packetSinkHelper (“ns3::TcpSocketFactory”, sinkAddress);

ApplicationContainer sinkApps = packetSinkHelper.Install (nodes.Get (3));

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 (0));

clientApps.Start (Seconds (2.0));

clientApps.Stop (Seconds (10.0));

// Enable tracing

AsciiTraceHelper ascii;

p2p.EnableAsciiAll (ascii.CreateFileStream (“ecmp-routing.tr”));

p2p.EnablePcapAll (“ecmp-routing”);

// Run the simulation

Simulator::Run ();

Simulator::Destroy ();

return 0;

}

Explanation

Here, the given below is the ECMP process description to execute the simulator:

1. Create Nodes and Links: The script creates four nodes and connects them with point-to-point links.
2. Install Internet Stack: The Internet stack is installed on the nodes using the InternetStackHelper.
3. Assign IP Addresses: IP addresses are assigned to the interfaces on the nodes.
4. Enable ECMP: The AddEcmpRoutes function is defined to add multiple routes to the static routing table of a node. This function is called to add multiple next-hop routes for the destination network 1.3.0/24.
5. Create Applications: A packet sink application is installed on node 3 to receive packets. An OnOff application is installed on node 0 to send packets to node 3.
6. Enable Tracing: ASCII and pcap tracing are enabled to capture the simulation output.
7. Run the Simulation: The simulation is run and then destroyed.

Running the Simulation

To run the simulation, compile the script and execute it:

./waf configure –enable-examples

./waf build

./waf –run ecmp-example

Overall, we had implemented the ECMP in ns3 simulator that creates nodes and links by following the ECMP functionalities. We also provide and support further support about how ECMP adapt in different environments. Simulating the ECMP in ns3 are carried on well by our developers so stay in touch with us.