ns3tcp-cwnd-test-suite.cc

Go to the documentation of this file.

/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2009 University of Washington
 *
 * 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
 */

#include "ns3/log.h"
#include "ns3/abort.h"
#include "ns3/test.h"
#include "ns3/pcap-file.h"
#include "ns3/config.h"
#include "ns3/string.h"
#include "ns3/uinteger.h"
#include "ns3/data-rate.h"
#include "ns3/inet-socket-address.h"
#include "ns3/point-to-point-helper.h"
#include "ns3/internet-stack-helper.h"
#include "ns3/ipv4-global-routing-helper.h"
#include "ns3/ipv4-address-helper.h"
#include "ns3/packet-sink-helper.h"
#include "ns3/tcp-socket-factory.h"
#include "ns3/traffic-control-helper.h"
#include "ns3/simulator.h"
#include "ns3/point-to-point-net-device.h"
#include "ns3/pointer.h"
#include "ns3/queue.h"

using namespace ns3;

NS_LOG_COMPONENT_DEFINE ("Ns3CwndTest");

// ===========================================================================
// This is a simple test to demonstrate how a known good model (a reference 
// implementation) may be used to test another model without resorting to 
// storing stimulus or response vectors.
//
// Node zero contains the model under test, in this case the ns-3 TCP 
// implementation.  Node one contains the reference implementation that we
// assume will generate good test vectors for us.  In this case, a Linux
// TCP implementation is used to stimulate the ns-3 TCP model with what we
// assume are perfectly good packets.  We watch the ns-3 implementation to
// see what it does in the presence of these assumed good stimuli.
//
// The test is arranged as a typical ns-3 script, but we use the trace system
// to peek into the running system and monitor the ns-3 TCP.
//
// The topology is just two nodes communicating over a point-to-point network.
// The point-to-point network is chosen because it is simple and allows us to
// easily generate pcap traces we can use to separately verify that the ns-3
// implementation is responding correctly.  Once the operation is verified, we
// enter a list of responses that capture the response succinctly.
//
//         node 0                 node 1
//   +----------------+    +----------------+
//   |    ns-3 TCP    |    |    Linux TCP   |
//   +----------------+    +----------------+
//   |    10.1.1.1    |    |    10.1.1.2    |
//   +----------------+    +----------------+
//   | point-to-point |    | point-to-point |
//   +----------------+    +----------------+
//           |                     |
//           +---------------------+
//                5 Mbps, 2 ms
//
// ===========================================================================
//
class SimpleSource : public Application 
{
public:

  SimpleSource ();
  virtual ~SimpleSource();

  static TypeId GetTypeId (void);
  
  void Setup (Ptr<Socket> socket, Address address, uint32_t packetSize, uint32_t nPackets, DataRate dataRate);

private:
  virtual void StartApplication (void);
  virtual void StopApplication (void);

  void ScheduleTx (void);
  void SendPacket (void);

  Ptr<Socket>     m_socket;
  Address         m_peer;
  uint32_t        m_packetSize;
  uint32_t        m_nPackets;
  DataRate        m_dataRate;
  EventId         m_sendEvent;
  bool            m_running;
  uint32_t        m_packetsSent;
};

SimpleSource::SimpleSource ()
  : m_socket (0), 
    m_peer (), 
    m_packetSize (0), 
    m_nPackets (0), 
    m_dataRate (0), 
    m_sendEvent (), 
    m_running (false), 
    m_packetsSent (0)
{
}

SimpleSource::~SimpleSource()
{
  m_socket = 0;
}

/* static */
TypeId
SimpleSource::GetTypeId (void)
{
  static TypeId tid = TypeId ("SimpleSource")
    .SetParent<Application> ()
    .SetGroupName ("Stats")
    .AddConstructor<SimpleSource> ()
    ;
  return tid;
}
  
void
SimpleSource::Setup (Ptr<Socket> socket, Address address, uint32_t packetSize, uint32_t nPackets, DataRate dataRate)
{
  m_socket = socket;
  m_peer = address;
  m_packetSize = packetSize;
  m_nPackets = nPackets;
  m_dataRate = dataRate;
}

void
SimpleSource::StartApplication (void)
{
  m_running = true;
  m_packetsSent = 0;
  m_socket->Bind ();
  m_socket->Connect (m_peer);
  SendPacket ();
}

void 
SimpleSource::StopApplication (void)
{
  m_running = false;

  if (m_sendEvent.IsRunning ())
    {
      Simulator::Cancel (m_sendEvent);
    }

  if (m_socket)
    {
      m_socket->Close ();
    }
}

void 
SimpleSource::SendPacket (void)
{
  Ptr<Packet> packet = Create<Packet> (m_packetSize);
  m_socket->Send (packet);

  if (++m_packetsSent < m_nPackets)
    {
      ScheduleTx ();
    }
}

void 
SimpleSource::ScheduleTx (void)
{
  if (m_running)
    {
      Time tNext (Seconds (m_packetSize * 8 / static_cast<double> (m_dataRate.GetBitRate ())));
      m_sendEvent = Simulator::Schedule (tNext, &SimpleSource::SendPacket, this);
    }
}

class Ns3TcpCwndTestCase1 : public TestCase
{
public:
  Ns3TcpCwndTestCase1 ();
  virtual ~Ns3TcpCwndTestCase1 ();

private:
  virtual void DoRun (void);
  bool m_writeResults;

  class CwndEvent {
public:
    uint32_t m_oldCwnd;
    uint32_t m_newCwnd;
  };

  TestVectors<CwndEvent> m_responses;

  void CwndChange (uint32_t oldCwnd, uint32_t newCwnd);
};

Ns3TcpCwndTestCase1::Ns3TcpCwndTestCase1 ()
  : TestCase ("Check to see that the ns-3 TCP congestion window works as expected against liblinux2.6.26.so"),
    m_writeResults (false)
{
}

Ns3TcpCwndTestCase1::~Ns3TcpCwndTestCase1 ()
{
}

void
Ns3TcpCwndTestCase1::CwndChange (uint32_t oldCwnd, uint32_t newCwnd)
{
  CwndEvent event;

  event.m_oldCwnd = oldCwnd;
  event.m_newCwnd = newCwnd;

  m_responses.Add (event);

  NS_LOG_DEBUG ("Cwnd change event " << m_responses.GetN () << " at " << Now ().As (Time::S) << " " << oldCwnd << " " << newCwnd);
}

void
Ns3TcpCwndTestCase1::DoRun (void)
{
  NS_LOG_DEBUG ("Starting test case 1");
  //
  // Create two nodes.  One (node zero) will be the node with the TCP
  // under test which is the ns-3 TCP implementation.  The other node (node
  // one) will be the node with the reference implementation we use to drive
  // the tests.
  //
  NodeContainer nodes;
  nodes.Create (2);

  //
  // For this test we'll use a point-to-point net device.  It's not as simple
  // as a simple-net-device, but it provides nice places to hook trace events
  // so we can see what's moving between our nodes.
  //
  PointToPointHelper pointToPoint;
  pointToPoint.SetDeviceAttribute ("DataRate", StringValue ("5Mbps"));
  pointToPoint.SetChannelAttribute ("Delay", StringValue ("2ms"));

  NetDeviceContainer devices;
  devices = pointToPoint.Install (nodes);

  //
  // Install two variants of the internet stack.  The first, on node zero 
  // uses the TCP under test, which is the default ns-3 TCP implementation.
  //
  InternetStackHelper stack;
  stack.Install (nodes.Get (0));

  //
  // The other node, node one, is going to be set up to use a Linux TCP
  // implementation that we consider a known good TCP.
  //
  std::string nscStack = "liblinux2.6.26.so";
  stack.SetTcp ("ns3::NscTcpL4Protocol", "Library", StringValue ("liblinux2.6.26.so"));
  stack.Install (nodes.Get (1));

  //
  // Assign the address 10.1.1.1 to the TCP implementation under test (index
  // zero) and 10.1.1.2 to the reference implementation (index one).
  //
  Ipv4AddressHelper address;
  address.SetBase ("10.1.1.0", "255.255.255.252");
  Ipv4InterfaceContainer interfaces = address.Assign (devices);

  //
  // We need a place to send our TCP data on the node with the reference TCP 
  // implementation.  We aren't really concerned about what happens there, so
  // just create a sink.
  //
  uint16_t sinkPort = 8080;
  Address sinkAddress (InetSocketAddress (interfaces.GetAddress (1), sinkPort));
  PacketSinkHelper packetSinkHelper ("ns3::TcpSocketFactory", InetSocketAddress (Ipv4Address::GetAny (), sinkPort));
  ApplicationContainer sinkApps = packetSinkHelper.Install (nodes.Get (1));
  sinkApps.Start (Seconds (0.));
  sinkApps.Stop (Seconds (1.1));

  //
  // This test uses a custom application that provides a direct handle to
  // the socket (the socket of applications such as the OnOffApplication
  // is not created until Application Start time, and is not easily accessible).
  //
  // So first, we create a socket and do the trace connect on it; then we pass this
  // socket into the constructor of our simple application which we then install
  // in the node with the ns-3 TCP.
  //
  Ptr<Socket> ns3TcpSocket = Socket::CreateSocket (nodes.Get (0), TcpSocketFactory::GetTypeId ());
  ns3TcpSocket->TraceConnectWithoutContext ("CongestionWindowInflated", MakeCallback (&Ns3TcpCwndTestCase1::CwndChange, this));

  Ptr<SimpleSource> app = CreateObject<SimpleSource> ();
  // 1040 is size of packet objects used to write data to the socket (note:
  // the actual TCP segment size will be 536 bytes).  10 is the number
  // of packets, so we write 10 * 1040 bytes.  This requires 20 segments
  // of payload size 536, with the last one being a partially full segment
  app->Setup (ns3TcpSocket, sinkAddress, 1040, 10, DataRate ("5Mbps"));
  nodes.Get (0)->AddApplication (app);
  app->SetStartTime (Seconds (1.));
  app->SetStopTime (Seconds (1.1));

  //
  // The idea here is that someone will look very closely at the all of the
  // communications between the reference TCP and the TCP under test in this
  // simulation and determine that all of the responses are correct.  We expect
  // that this means generating a pcap trace file from the point-to-point link
  // and examining the packets closely using tcpdump, wireshark or some such
  // program.  So we provide the ability to generate a pcap trace of the 
  // test execution for your perusal.
  //
  // Once the validation test is determined to be running exactly as expected,
  // the set of congestion window changes is collected and hard coded into the 
  // test results which will then be checked during the actual execution of the
  // test.
  //

  if (m_writeResults)
    {
      pointToPoint.EnablePcapAll ("tcp-cwnd");
    }

  Simulator::Stop (Seconds (2));
  Simulator::Run ();
  Simulator::Destroy ();

  //
  // As new acks are received by the TCP under test, the congestion window 
  // should be opened up by one segment (MSS bytes) each time.  This should
  // trigger a congestion window change event which we hooked and saved above.
  // We should now be able to look through the saved response vectors and follow
  // the congestion window as it opens up when the ns-3 TCP under test 
  // transmits its bits
  //
  // From inspecting the results, we know that we should see N_EVENTS congestion
  // window change events (each time by MSS bytes) until reaching the largest
  // value when the client closes.
  //
  const uint32_t MSS = 536;
  const uint32_t N_EVENTS = 20;

  CwndEvent event;

  NS_TEST_ASSERT_MSG_EQ (m_responses.GetN (), N_EVENTS, "Unexpectedly low number of cwnd change events");

  // Ignore the first event logged (i=0) when m_cWnd goes from 0 to MSS bytes
  for (uint32_t i = 1, from = MSS, to = MSS * 2; i < N_EVENTS; ++i, from += MSS, to += MSS)
    {
      event = m_responses.Get (i);
      NS_TEST_ASSERT_MSG_EQ (event.m_oldCwnd, from, "Wrong old cwnd value in cwnd change event " << i);
      NS_TEST_ASSERT_MSG_EQ (event.m_newCwnd, to, "Wrong new cwnd value in cwnd change event " << i);
    }
}


// ===========================================================================
// Test case for cwnd changes due to out-of-order packets. A bottleneck 
// link is created, and a limited droptail queue is used in order to 
// force dropped packets, resulting in out-of-order packet delivery. 
// This out-of-order delivery will result in a different congestion 
// window behavior than testcase 1.  Specifically, duplicate ACKs
// are encountered.
//
// Network topology
//
//        1Mb/s, 10ms      100kb/s, 10ms     1Mb/s, 10ms
//    n0--------------n1-----------------n2---------------n3
//
// ===========================================================================
class Ns3TcpCwndTestCase2 : public TestCase
{
public:
  Ns3TcpCwndTestCase2 ();
  virtual ~Ns3TcpCwndTestCase2 ();

private:
  virtual void DoRun (void);
  void VerifyCwndRun (uint32_t beginIdx, uint32_t endIdx, uint32_t initialCwnd, uint32_t mss);
  bool m_writeResults;

  class CwndEvent {
public:
    uint32_t m_oldCwnd;
    uint32_t m_newCwnd;
  };

  TestVectors<CwndEvent> m_responses;

  void CwndChange (uint32_t oldCwnd, uint32_t newCwnd);
  void CwndChangeNotInflated (uint32_t oldCwnd, uint32_t newCwnd);
};

Ns3TcpCwndTestCase2::Ns3TcpCwndTestCase2 ()
  : TestCase ("Check to see that the ns-3 TCP congestion window works as expected for out-of-order packet delivery"),
    m_writeResults (false)
{
}

Ns3TcpCwndTestCase2::~Ns3TcpCwndTestCase2 ()
{
}

void
Ns3TcpCwndTestCase2::CwndChange (uint32_t oldCwnd, uint32_t newCwnd)
{
  CwndEvent event;

  event.m_oldCwnd = oldCwnd;
  event.m_newCwnd = newCwnd;

  m_responses.Add (event);
  NS_LOG_DEBUG ("Cwnd change event " << m_responses.GetN () << " at " << Now ().As (Time::S) << " " << oldCwnd << " " << newCwnd);
}

void
Ns3TcpCwndTestCase2::CwndChangeNotInflated (uint32_t oldCwnd, uint32_t newCwnd)
{
  NS_LOG_DEBUG ("Cwnd NOT INFLATED change event " << m_responses.GetN () << " at " << Now ().As (Time::S) << " " << oldCwnd << " " << newCwnd);
}

void
Ns3TcpCwndTestCase2::DoRun (void)
{ 
  NS_LOG_DEBUG ("Starting test case 2");
  // Set up some default values for the simulation.
  Config::SetDefault ("ns3::QueueBase::MaxSize", QueueSizeValue (QueueSize (QueueSizeUnit::PACKETS, 4)));
  Packet::EnablePrinting ();

  NodeContainer n0n1;
  n0n1.Create (2);

  NodeContainer n1n2;
  n1n2.Add (n0n1.Get (1));
  n1n2.Create (1);

  NodeContainer n2n3;
  n2n3.Add (n1n2.Get (1));
  n2n3.Create (1);

  PointToPointHelper p2p1;
  p2p1.SetDeviceAttribute ("DataRate", DataRateValue (DataRate (1000000)));
  p2p1.SetChannelAttribute ("Delay", TimeValue (MilliSeconds (10)));
  PointToPointHelper p2p2;
  p2p2.SetDeviceAttribute ("DataRate", DataRateValue (DataRate (100000)));
  p2p2.SetChannelAttribute ("Delay", TimeValue (MilliSeconds (10)));

  // And then install devices and channels connecting our topology.
  NetDeviceContainer dev0 = p2p1.Install (n0n1);
  NetDeviceContainer dev1 = p2p2.Install (n1n2);
  NetDeviceContainer dev2 = p2p1.Install (n2n3);

  // Now add ip/tcp stack to all nodes.
  InternetStackHelper internet;
  internet.InstallAll ();

  // Later, we add IP addresses.
  Ipv4AddressHelper ipv4;
  ipv4.SetBase ("10.1.3.0", "255.255.255.0");
  ipv4.Assign (dev0);
  ipv4.SetBase ("10.1.2.0", "255.255.255.0");
  ipv4.Assign (dev1);
  ipv4.SetBase ("10.1.1.0", "255.255.255.0");
  Ipv4InterfaceContainer ipInterfs = ipv4.Assign (dev2);

  // and setup ip routing tables to get total ip-level connectivity.
  Ipv4GlobalRoutingHelper::PopulateRoutingTables ();

  // Disable traffic control layer so that drops occur
  TrafficControlHelper tch;
  tch.Uninstall (dev0);
  tch.Uninstall (dev1);
  tch.Uninstall (dev2);

  // Set up the apps
  uint16_t servPort = 50000;

  // Create a packet sink to receive these packets on n3
  PacketSinkHelper sink ("ns3::TcpSocketFactory",
                         InetSocketAddress (Ipv4Address::GetAny (), servPort));

  ApplicationContainer apps = sink.Install (n2n3.Get (1));
  apps.Start (Seconds (0.0));
  apps.Stop (Seconds (5.4));

  // Create the socket for n0
  Address sinkAddress (InetSocketAddress (ipInterfs.GetAddress (1), servPort));
  Ptr<Socket> ns3TcpSocket = Socket::CreateSocket (n0n1.Get (0), TcpSocketFactory::GetTypeId ());
  // Disable SACK because this test is testing NewReno behavior
  ns3TcpSocket->SetAttribute ("Sack", BooleanValue (false));
  ns3TcpSocket->TraceConnectWithoutContext ("CongestionWindowInflated", MakeCallback (&Ns3TcpCwndTestCase2::CwndChange, this));
  ns3TcpSocket->TraceConnectWithoutContext ("CongestionWindow", MakeCallback (&Ns3TcpCwndTestCase2::CwndChangeNotInflated, this));

  // Create and start the app for n0
  Ptr<SimpleSource> app = CreateObject<SimpleSource> ();
  app->Setup (ns3TcpSocket, sinkAddress, 1040, 1000, DataRate ("1Mbps"));
  n0n1.Get (0)->AddApplication (app);
  app->SetStartTime (Seconds (1.0));
  app->SetStopTime (Seconds (4.1));

  if (m_writeResults)
    {
      // Write a pcap for tcp cwnd testcase with out-of-order delivery
      PointToPointHelper pointToPoint;
      pointToPoint.EnablePcapAll ("tcp-cwnd-ood");
    }

  // Finally, set up the simulator to run.
  Simulator::Stop (Seconds (4.1));
  Simulator::Run ();
  Simulator::Destroy ();

  //
  // As new acks are received by the TCP under test, the congestion window 
  // should be opened up by one segment (MSS bytes) each time.  This should
  // trigger a congestion window change event which we hooked and saved above.
  // We should now be able to look through the saved response vectors and follow
  // the congestion window as it opens up when the ns-3 TCP under test 
  // transmits its bits
  //
  // From inspecting the results, we know that we should see N_EVENTS congestion
  // window change events. On the tenth change event, the window should 
  // be cut from 5360 to 4288 due to 3 dup acks (NewReno behavior is to
  // cut in half, and then add 3 segments (5360/2 + 3*536 = 4288)
  //
  
  const uint32_t MSS = 536;
  const uint32_t N_EVENTS = 38;

  CwndEvent event;

  NS_LOG_DEBUG ("Number of response events: " << m_responses.GetN ());
  //NS_TEST_ASSERT_MSG_EQ (m_responses.GetN (), N_EVENTS, "Unexpected number of cwnd change events");

  // Ignore the first event logged (i=0) when m_cWnd goes from 0 to MSS bytes
  VerifyCwndRun (1, 10, 2 * MSS, MSS);
  
  // At the point of loss, sndNxt = 15545; sndUna = 9113.  FlightSize is 4824, 
  // so there are 9 segments outstanding.  Cut ssthresh to 9/2 (2412) and 
  // cwnd to (9/2 + 3) = 4020
  event = m_responses.Get (10);
  NS_TEST_ASSERT_MSG_EQ (event.m_newCwnd, (MSS * 15)/2, "Wrong new cwnd value in cwnd change event " << 10);

  // Verify that cwnd increments by one for a few segments
  // from 8.5 at index 11 to 12.5 at index 15
  VerifyCwndRun (11, 15, (MSS * 17)/2, MSS);

  // partial ack at event 16, cwnd reset from 6700 (12.5*MSS) to 5092 (9.5*MSS)
  NS_TEST_ASSERT_MSG_EQ (m_responses.Get (16).m_newCwnd, (MSS * 19)/2, "Wrong new cwnd value in cwnd change event " << 16);

  // partial ack again of 3 segments after one more acks, cwnd reset to 7.5 
  NS_TEST_ASSERT_MSG_EQ (m_responses.Get (18).m_newCwnd, (MSS * 15)/2, "Wrong new cwnd value in cwnd change event " << 18);

  //DUP ACKS in remaining fast recovery
  VerifyCwndRun (18, 20, (MSS * 15)/2, MSS);

  // Process another partial ack
  VerifyCwndRun (21, 24, (MSS * 13)/2, MSS);
 
  // Leaving fast recovery at event 25; set cwnd to 4 segments as per RFC 2582
  // Sec. 3 para. 5 option 2 (sshthresh is 2412, 4.5 times MSS)
  NS_TEST_ASSERT_MSG_EQ (m_responses.Get (25).m_newCwnd,  2412, "Wrong new cwnd value in cwnd change event " << 25);
  
  //In CongAvoid each event will increase cwnd by (MSS * MSS / cwnd)
  uint32_t cwnd = 2412;
  for (uint32_t i = 26; i < N_EVENTS; ++i)
    {
      double adder = static_cast<double> (MSS * MSS) / cwnd;
      adder = std::max (1.0, adder);
      cwnd += static_cast<uint32_t> (adder);    
      NS_TEST_ASSERT_MSG_EQ (m_responses.Get (i).m_newCwnd, cwnd, "Wrong new cwnd value in cwnd change event " << i); 
    }
  NS_LOG_DEBUG ("Reading out the cwnd event log");  
  for (uint32_t i = 0; i < N_EVENTS; ++i)
  {
    NS_LOG_DEBUG ("i: " << i << " newCwnd: " << m_responses.Get(i).m_newCwnd << " newCwnd segments " << static_cast<double> (m_responses.Get(i).m_newCwnd)/MSS);
  }
}

void 
Ns3TcpCwndTestCase2::VerifyCwndRun (uint32_t beginIdx, uint32_t endIdx, uint32_t initialCwnd, uint32_t mss)
{

  CwndEvent event;
  
  for(uint32_t i = beginIdx, to = initialCwnd; i < endIdx; ++i, to += mss)
    {
      event = m_responses.Get (i);
      NS_TEST_ASSERT_MSG_EQ (event.m_newCwnd, to, "Wrong new cwnd value in cwnd change event " << i);      
    }
}

class Ns3TcpCwndTestSuite : public TestSuite
{
public:
  Ns3TcpCwndTestSuite ();
};

Ns3TcpCwndTestSuite::Ns3TcpCwndTestSuite ()
  : TestSuite ("ns3-tcp-cwnd", SYSTEM)
{
  AddTestCase (new Ns3TcpCwndTestCase1, TestCase::QUICK);
  AddTestCase (new Ns3TcpCwndTestCase2, TestCase::QUICK);
}

Ns3TcpCwndTestSuite ns3TcpCwndTestSuite;