tcp-pacing.cc

Go to the documentation of this file.

/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2020 NITK Surathkal
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation;
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Authors: Vivek Jain <jain.vivek.anand@gmail.com>
 *          Deepak Kumaraswamy <deepakkavoor99@gmail.com>
 */

// The following network topology is used in this example, and is taken from
// Figure 2 of https://homes.cs.washington.edu/~tom/pubs/pacing.pdf
//
//    n0                          n4
//    |                           |
//    |(4x Mbps, 5ms)             |(4x Mbps, 5ms)
//    |                           |
//    |                           |
//    |      (x Mbps, 40ms)       |
//    n2 ------------------------ n3
//    |                           |
//    |                           |
//    |(4x Mbps, 5ms)             |(4x Mbps, 5ms)
//    |                           |
//    n1                          n5
//
//

// This example illustrates how TCP pacing can be enabled on a socket.
// Two long-running TCP flows are instantiated at nodes n0 and n1 to
// send data over a bottleneck link (n2->n3) to sink nodes n4 and n5.
// At the end of the simulation, the IP-level flow monitor tool will
// print out summary statistics of the flows.  The flow monitor detects
// four flows, but that is because the flow records are unidirectional;
// the latter two flows reported are actually ack streams.
//
// At the end of this simulation, data files are also generated
// that track changes in Congestion Window, Slow Start threshold and
// TCP pacing rate for the first flow (n0). Additionally, a data file
// that contains information about packet transmission and reception times
// (collected through TxTrace and RxTrace respectively) is also produced.
// This transmission and reception (ack) trace is the most direct way to
// observe the effects of pacing.  All the above information is traced
// just for the single node n0.
//
// A small amount of randomness is introduced to the program to control
// the start time of the flows.
//
// This example has pacing enabled by default, which means that TCP
// does not send packets back-to-back, but instead paces them out over
// an RTT. The size of initial congestion window is set to 10, and pacing
// of the initial window is enabled. The available command-line options and
// their default values can be observed in the usual way by running the
// program to print the help info; i.e.: ./waf --run 'tcp-pacing --PrintHelp'
//
// When pacing is disabled, TCP sends eligible packets back-to-back. The
// differences in behaviour when pacing is disabled can be observed from the
// packet transmission data file. For instance, one can observe that
// packets in the initial window are sent one after the other simultaneously,
// without any inter-packet gaps. Another instance is when n0 receives a
// packet in the form of an acknowledgement, and sends out data packets without
// pacing them.
//
// Although this example serves as a useful demonstration of how pacing could
// be enabled/disabled in ns-3 TCP congestion controls, we could not observe
// significant improvements in throughput for the above topology when pacing
// was enabled. In future, one could try and incorporate models such as
// TCP Prague and ACK-filtering, which may show a stronger performance
// impact for TCP pacing.

#include <iomanip>
#include <iostream>
#include <string>
#include <fstream>
#include "ns3/core-module.h"
#include "ns3/point-to-point-module.h"
#include "ns3/internet-module.h"
#include "ns3/applications-module.h"
#include "ns3/network-module.h"
#include "ns3/packet-sink.h"
#include "ns3/flow-monitor-module.h"
#include "ns3/ipv4-global-routing-helper.h"
#include "ns3/traffic-control-module.h"

using namespace ns3;

NS_LOG_COMPONENT_DEFINE ("TcpPacingExample");

std::ofstream cwndStream;
std::ofstream pacingRateStream;
std::ofstream ssThreshStream;
std::ofstream packetTraceStream;

static void
CwndTracer (uint32_t oldval, uint32_t newval)
{
  cwndStream << std::fixed << std::setprecision (6) << Simulator::Now ().GetSeconds () << std::setw (12) << newval << std::endl;
}

static void
PacingRateTracer (DataRate oldval, DataRate newval)
{
  pacingRateStream << std::fixed << std::setprecision (6) << Simulator::Now ().GetSeconds () << std::setw (12) << newval.GetBitRate () / 1e6 << std::endl;
}

static void
SsThreshTracer (uint32_t oldval, uint32_t newval)
{
  ssThreshStream << std::fixed << std::setprecision (6) << Simulator::Now ().GetSeconds () << std::setw (12) << newval << std::endl;
}

static void
TxTracer (Ptr<const Packet> p, Ptr<Ipv4> ipv4, uint32_t interface)
{
  packetTraceStream << std::fixed << std::setprecision (6) << Simulator::Now ().GetSeconds () << " tx " << p->GetSize () << std::endl;
}

static void
RxTracer (Ptr<const Packet> p, Ptr<Ipv4> ipv4, uint32_t interface)
{
  packetTraceStream << std::fixed << std::setprecision (6) << Simulator::Now ().GetSeconds () << " rx " << p->GetSize () << std::endl;
}

void
ConnectSocketTraces (void)
{
  Config::ConnectWithoutContext ("/NodeList/0/$ns3::TcpL4Protocol/SocketList/0/CongestionWindow", MakeCallback (&CwndTracer));
  Config::ConnectWithoutContext ("/NodeList/0/$ns3::TcpL4Protocol/SocketList/0/PacingRate", MakeCallback (&PacingRateTracer));
  Config::ConnectWithoutContext ("/NodeList/0/$ns3::TcpL4Protocol/SocketList/0/SlowStartThreshold", MakeCallback (&SsThreshTracer));
  Config::ConnectWithoutContext ("/NodeList/0/$ns3::Ipv4L3Protocol/Tx", MakeCallback (&TxTracer));
  Config::ConnectWithoutContext ("/NodeList/0/$ns3::Ipv4L3Protocol/Rx", MakeCallback (&RxTracer));
}

int
main (int argc, char *argv[])
{
  bool tracing = false;

  uint32_t maxBytes = 0; // value of zero corresponds to unlimited send
  std::string transportProtocol = "ns3::TcpCubic";

  Time simulationEndTime = Seconds (5);
  DataRate bottleneckBandwidth ("10Mbps");  // value of x as shown in the above network topology
  Time bottleneckDelay = MilliSeconds (40);
  DataRate regLinkBandwidth = DataRate (4 * bottleneckBandwidth.GetBitRate ());
  Time regLinkDelay = MilliSeconds (5);
  DataRate maxPacingRate ("4Gbps");

  bool isPacingEnabled = true;
  bool useEcn = true;
  bool useQueueDisc = true;
  bool shouldPaceInitialWindow = true;

  // Configure defaults that are not based on explicit command-line arguments
  // They may be overridden by general attribute configuration of command line
  Config::SetDefault ("ns3::TcpL4Protocol::SocketType", TypeIdValue (TypeId::LookupByName (transportProtocol)));
  Config::SetDefault ("ns3::TcpSocket::InitialCwnd", UintegerValue (10));

  CommandLine cmd (__FILE__);
  cmd.AddValue ("tracing", "Flag to enable/disable Ascii and Pcap tracing", tracing);
  cmd.AddValue ("maxBytes", "Total number of bytes for application to send", maxBytes);
  cmd.AddValue ("isPacingEnabled", "Flag to enable/disable pacing in TCP", isPacingEnabled);
  cmd.AddValue ("maxPacingRate", "Max Pacing Rate", maxPacingRate);
  cmd.AddValue ("useEcn", "Flag to enable/disable ECN", useEcn);
  cmd.AddValue ("useQueueDisc", "Flag to enable/disable queue disc on bottleneck", useQueueDisc);
  cmd.AddValue ("shouldPaceInitialWindow", "Flag to enable/disable pacing of TCP initial window", shouldPaceInitialWindow);
  cmd.AddValue ("simulationEndTime", "Simulation end time", simulationEndTime);
  cmd.Parse (argc, argv);

  // Configure defaults based on command-line arguments
  Config::SetDefault ("ns3::TcpSocketState::EnablePacing", BooleanValue (isPacingEnabled));
  Config::SetDefault ("ns3::TcpSocketState::PaceInitialWindow", BooleanValue (shouldPaceInitialWindow));
  Config::SetDefault ("ns3::TcpSocketBase::UseEcn", (useEcn ? EnumValue (TcpSocketState::On) : EnumValue (TcpSocketState::Off)));
  Config::SetDefault ("ns3::TcpSocketState::MaxPacingRate", DataRateValue (maxPacingRate));

  NS_LOG_INFO ("Create nodes.");
  NodeContainer c;
  c.Create (6);

  NS_LOG_INFO ("Create channels.");
  NodeContainer n0n2 = NodeContainer (c.Get (0), c.Get (2));
  NodeContainer n1n2 = NodeContainer (c.Get (1), c.Get (2));

  NodeContainer n2n3 = NodeContainer (c.Get (2), c.Get (3));

  NodeContainer n3n4 = NodeContainer (c.Get (3), c.Get (4));
  NodeContainer n3n5 = NodeContainer (c.Get (3), c.Get (5));

  //Define Node link properties
  PointToPointHelper regLink;
  regLink.SetDeviceAttribute ("DataRate", DataRateValue (regLinkBandwidth));
  regLink.SetChannelAttribute ("Delay", TimeValue (regLinkDelay));

  NetDeviceContainer d0d2 = regLink.Install (n0n2);
  NetDeviceContainer d1d2 = regLink.Install (n1n2);
  NetDeviceContainer d3d4 = regLink.Install (n3n4);
  NetDeviceContainer d3d5 = regLink.Install (n3n5);

  PointToPointHelper bottleNeckLink;
  bottleNeckLink.SetDeviceAttribute ("DataRate", DataRateValue (bottleneckBandwidth));
  bottleNeckLink.SetChannelAttribute ("Delay", TimeValue (bottleneckDelay));

  NetDeviceContainer d2d3 = bottleNeckLink.Install (n2n3);

  //Install Internet stack
  InternetStackHelper stack;
  stack.Install (c);

  // Install traffic control
  if (useQueueDisc)
    {
      TrafficControlHelper tchBottleneck;
      tchBottleneck.SetRootQueueDisc ("ns3::FqCoDelQueueDisc");
      tchBottleneck.Install (d2d3);
    }

  NS_LOG_INFO ("Assign IP Addresses.");
  Ipv4AddressHelper ipv4;
  ipv4.SetBase ("10.1.1.0", "255.255.255.0");
  Ipv4InterfaceContainer regLinkInterface0 = ipv4.Assign (d0d2);

  ipv4.SetBase ("10.1.2.0", "255.255.255.0");
  Ipv4InterfaceContainer regLinkInterface1 = ipv4.Assign (d1d2);

  ipv4.SetBase ("10.1.3.0", "255.255.255.0");
  Ipv4InterfaceContainer bottleneckInterface = ipv4.Assign (d2d3);

  ipv4.SetBase ("10.1.4.0", "255.255.255.0");
  Ipv4InterfaceContainer regLinkInterface4 = ipv4.Assign (d3d4);

  ipv4.SetBase ("10.1.5.0", "255.255.255.0");
  Ipv4InterfaceContainer regLinkInterface5 = ipv4.Assign (d3d5);

  Ipv4GlobalRoutingHelper::PopulateRoutingTables ();

  NS_LOG_INFO ("Create Applications.");

  // Two Sink Applications at n4 and n5
  uint16_t sinkPort = 8080;
  Address sinkAddress4 (InetSocketAddress (regLinkInterface4.GetAddress (1), sinkPort)); // interface of n4
  Address sinkAddress5 (InetSocketAddress (regLinkInterface5.GetAddress (1), sinkPort)); // interface of n5
  PacketSinkHelper packetSinkHelper ("ns3::TcpSocketFactory", InetSocketAddress (Ipv4Address::GetAny (), sinkPort));
  ApplicationContainer sinkApps4 = packetSinkHelper.Install (c.Get (4)); //n4 as sink
  ApplicationContainer sinkApps5 = packetSinkHelper.Install (c.Get (5)); //n5 as sink

  sinkApps4.Start (Seconds (0));
  sinkApps4.Stop (simulationEndTime);
  sinkApps5.Start (Seconds (0));
  sinkApps5.Stop (simulationEndTime);

  // Randomize the start time between 0 and 1ms
  Ptr<UniformRandomVariable> uniformRv = CreateObject<UniformRandomVariable> ();
  uniformRv->SetStream (0);

  // Two Source Applications at n0 and n1
  BulkSendHelper source0 ("ns3::TcpSocketFactory", sinkAddress4);
  BulkSendHelper source1 ("ns3::TcpSocketFactory", sinkAddress5);
  // Set the amount of data to send in bytes.  Zero is unlimited.
  source0.SetAttribute ("MaxBytes", UintegerValue (maxBytes));
  source1.SetAttribute ("MaxBytes", UintegerValue (maxBytes));
  ApplicationContainer sourceApps0 = source0.Install (c.Get (0));
  ApplicationContainer sourceApps1 = source1.Install (c.Get (1));

  sourceApps0.Start (MicroSeconds (uniformRv->GetInteger (0, 1000)));
  sourceApps0.Stop (simulationEndTime);
  sourceApps1.Start (MicroSeconds (uniformRv->GetInteger (0, 1000)));
  sourceApps1.Stop (simulationEndTime);

  if (tracing)
    {
      AsciiTraceHelper ascii;
      regLink.EnableAsciiAll (ascii.CreateFileStream ("tcp-dynamic-pacing.tr"));
      regLink.EnablePcapAll ("tcp-dynamic-pacing", false);
    }

  cwndStream.open ("tcp-dynamic-pacing-cwnd.dat", std::ios::out);
  cwndStream << "#Time(s) Congestion Window (B)" << std::endl;

  pacingRateStream.open ("tcp-dynamic-pacing-pacing-rate.dat", std::ios::out);
  pacingRateStream << "#Time(s) Pacing Rate (Mb/s)" << std::endl;

  ssThreshStream.open ("tcp-dynamic-pacing-ssthresh.dat", std::ios::out);
  ssThreshStream << "#Time(s) Slow Start threshold (B)" << std::endl;

  packetTraceStream.open ("tcp-dynamic-pacing-packet-trace.dat", std::ios::out);
  packetTraceStream << "#Time(s) tx/rx size (B)" << std::endl;

  Simulator::Schedule (MicroSeconds (1001), &ConnectSocketTraces);

  FlowMonitorHelper flowmon;
  Ptr<FlowMonitor> monitor = flowmon.InstallAll ();

  NS_LOG_INFO ("Run Simulation.");
  Simulator::Stop (simulationEndTime);
  Simulator::Run ();

  monitor->CheckForLostPackets ();
  Ptr<Ipv4FlowClassifier> classifier = DynamicCast<Ipv4FlowClassifier> (flowmon.GetClassifier ());
  FlowMonitor::FlowStatsContainer stats = monitor->GetFlowStats ();
  for (std::map<FlowId, FlowMonitor::FlowStats>::const_iterator i = stats.begin (); i != stats.end (); ++i)
    {
      Ipv4FlowClassifier::FiveTuple t = classifier->FindFlow (i->first);

      std::cout << "Flow " << i->first  << " (" << t.sourceAddress << " -> " << t.destinationAddress << ")\n";
      std::cout << "  Tx Packets: " << i->second.txPackets << "\n";
      std::cout << "  Tx Bytes:   " << i->second.txBytes << "\n";
      std::cout << "  TxOffered:  " << i->second.txBytes * 8.0 / simulationEndTime.GetSeconds () / 1000 / 1000  << " Mbps\n";
      std::cout << "  Rx Packets: " << i->second.rxPackets << "\n";
      std::cout << "  Rx Bytes:   " << i->second.rxBytes << "\n";
      std::cout << "  Throughput: " << i->second.rxBytes * 8.0 / simulationEndTime.GetSeconds () / 1000 / 1000  << " Mbps\n";
    }


  cwndStream.close ();
  pacingRateStream.close ();
  ssThreshStream.close ();
  Simulator::Destroy ();
}