NS3: Dynamically Change the bandwidth

Based on https://blog.csdn.net/u010643777/article/details/80590045, I wrote this lab

[topology]

N0(TCP Sender)----P2Plink(5Mbps,2ms)---N1(TCP Sink)

At 5^th second, I will change the bandwidth of P2Plink from 5Mbps to 1000000bps.

test-change-bandwidth.cc (put this file under scratch)

#include <fstream>

#include <string.h>

#include "ns3/core-module.h"

#include "ns3/internet-module.h"

#include "ns3/point-to-point-module.h"

#include "ns3/packet-sink.h"

#include "ns3/packet-sink-helper.h"

#include "ns3/applications-module.h"

using namespace ns3;

NS_LOG_COMPONENT_DEFINE ("ThroughputTCP");

Ptr<PacketSink> sink; /* Pointer to the packet sink application */

uint64_t lastTotalRx = 0; /* The value of the last total received bytes */

void

CalculateThroughput ()

{

Time now = Simulator::Now (); /* Return the simulator's virtual time. */

double cur = (sink->GetTotalRx () - lastTotalRx) * (double) 8 / 1e6; /* Convert Application RX Packets to MBits. */

std::cout << now.GetSeconds () << "\t" << cur << std::endl;

lastTotalRx = sink->GetTotalRx ();

Simulator::Schedule (MilliSeconds (1000), &CalculateThroughput);

}

void

ChangeBandwith(Ptr<NetDevice> netdevice, uint64_t bps)

{

PointToPointNetDevice *device=static_cast<PointToPointNetDevice *>(PeekPointer(netdevice));

device->SetDataRate(DataRate(bps));

}

int

main (int argc, char *argv[])

{

NS_LOG_INFO ("Create nodes.");

NodeContainer n;

n.Create (2);

InternetStackHelper internet;

internet.Install (n);

NS_LOG_INFO ("Create channels.");

PointToPointHelper pointToPoint;

pointToPoint.SetDeviceAttribute ("DataRate", StringValue ("5Mbps"));

pointToPoint.SetChannelAttribute ("Delay", StringValue ("2ms"));

pointToPoint.SetDeviceAttribute("Mtu", UintegerValue(1400));

NetDeviceContainer p2pDevices;

p2pDevices = pointToPoint.Install (n);

Ipv4AddressHelper ipv4;

NS_LOG_INFO ("Assign IP Addresses.");

ipv4.SetBase ("10.1.1.0", "255.255.255.0");

Ipv4InterfaceContainer i = ipv4.Assign (p2pDevices);

NS_LOG_INFO ("Create Applications.");

PacketSinkHelper sinkHelper ("ns3::TcpSocketFactory", InetSocketAddress (Ipv4Address::GetAny (), 9));

ApplicationContainer sinkApp = sinkHelper.Install (n.Get(1));

sink = StaticCast<PacketSink> (sinkApp.Get (0));

BulkSendHelper source ("ns3::TcpSocketFactory", (InetSocketAddress (i.GetAddress (1), 9)));

source.SetAttribute ("MaxBytes", UintegerValue (0));

ApplicationContainer sourceApps = source.Install (n.Get (0));

sourceApps.Start (Seconds (1.0));

sourceApps.Stop (Seconds (15.0));

sinkApp.Start (Seconds (0.0));

Simulator::Schedule (Seconds (1.0), &CalculateThroughput);

//At 5th second, change the bandwidth from 5Mbps to 1000000bps

Simulator::Schedule (Seconds (5.0), &ChangeBandwith, p2pDevices.Get(0), 1000000);

Simulator::Stop (Seconds (16.0));

NS_LOG_INFO ("Run Simulation.");

Simulator::Run ();

Simulator::Destroy ();

NS_LOG_INFO ("Done.");

}

Execution

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Last Modified: 2022/2/14

Dr. Chih-Heng Ke

Department of Computer Science and Information Engineering, National Quemoy University, Kinmen, Taiwan

Email: smallko@gmail.com