tcp-pacing-test.cc

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/* -*-  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: Deepak Kumaraswamy <deepakkavoor99@gmail.com>
 *
 */
#include "ns3/log.h"
#include "ns3/simple-channel.h"
#include "ns3/config.h"
#include "ns3/test.h"
#include "tcp-general-test.h"
 
using namespace ns3;
 
NS_LOG_COMPONENT_DEFINE ("TcpPacingTestSuite");
 
class
TcpPacingTest : public TcpGeneralTest
{
public:
  TcpPacingTest (uint32_t segmentSize, uint32_t packetSize,
                 uint32_t packets, uint16_t pacingSsRatio, uint16_t pacingCaRatio,
                 uint32_t ssThresh, bool paceInitialWindow, uint32_t delAckMaxCount,
                 const TypeId& congControl, const std::string &desc);
 
protected:
  virtual void CWndTrace (uint32_t oldValue, uint32_t newValue);
  virtual void RttTrace (Time oldTime, Time newTime);
  virtual void BytesInFlightTrace (uint32_t oldValue, uint32_t newValue);
  virtual void Tx (const Ptr<const Packet> p, const TcpHeader &h, SocketWho who);
  virtual void Rx (const Ptr<const Packet> p, const TcpHeader &h, SocketWho who);
  virtual void QueueDrop (SocketWho who);
  virtual void PhyDrop (SocketWho who);
  virtual void NormalClose (SocketWho who);
 
  virtual void UpdateExpectedInterval (void);
 
  virtual void ConfigureEnvironment ();
  virtual void ConfigureProperties ();
 
private:
  uint32_t m_segmentSize;             
  uint32_t m_packetSize;              
  uint32_t m_packets;                 
  EventId  m_event;                   
  bool     m_initial;                 
  uint32_t m_initialCwnd;             
  uint32_t m_curCwnd;                 
  bool     m_isFullCwndSent;          
  uint32_t m_bytesInFlight;           
  Time     m_prevTxTime;              
  uint16_t m_pacingSsRatio;           
  uint16_t m_pacingCaRatio;           
  uint32_t m_ssThresh;                
  bool     m_paceInitialWindow;       
  uint32_t m_delAckMaxCount;          
  bool     m_isConnAboutToEnd;        
  Time     m_transmissionStartTime;   
  Time     m_expectedInterval;        
  uint32_t m_packetsSent;             
  Time     m_nextPacketInterval;      
  Time     m_tracedRtt;               
};
 
 
TcpPacingTest::TcpPacingTest (uint32_t segmentSize,
                              uint32_t packetSize,
                              uint32_t packets,
                              uint16_t pacingSsRatio,
                              uint16_t pacingCaRatio,
                              uint32_t ssThresh,
                              bool paceInitialWindow,
                              uint32_t delAckMaxCount,
                              const TypeId &typeId,
                              const std::string &desc)
  : TcpGeneralTest (desc),
    m_segmentSize (segmentSize),
    m_packetSize (packetSize),
    m_packets (packets),
    m_initial (true),
    m_initialCwnd (10),
    m_curCwnd (0),
    m_isFullCwndSent (true),
    m_bytesInFlight (0),
    m_prevTxTime (0),
    m_pacingSsRatio (pacingSsRatio),
    m_pacingCaRatio (pacingCaRatio),
    m_ssThresh (ssThresh),
    m_paceInitialWindow (paceInitialWindow),
    m_delAckMaxCount (delAckMaxCount),
    m_isConnAboutToEnd (false),
    m_transmissionStartTime (Seconds (0)),
    m_expectedInterval (Seconds (0)),
    m_packetsSent (0),
    m_nextPacketInterval (Seconds (0)),
    m_tracedRtt (Seconds (0))
{
  m_congControlTypeId = typeId;
}
 
void
TcpPacingTest::ConfigureEnvironment ()
{
  TcpGeneralTest::ConfigureEnvironment ();
  SetAppPktSize (m_packetSize);
  SetAppPktCount (m_packets);
  SetAppPktInterval (NanoSeconds (10));
  SetMTU (1500);
  SetTransmitStart (Seconds (0));
  SetPropagationDelay (MilliSeconds (50));
}
 
void TcpPacingTest::ConfigureProperties ()
{
  TcpGeneralTest::ConfigureProperties ();
  SetSegmentSize (SENDER, m_segmentSize);
  SetInitialSsThresh (SENDER, m_ssThresh);
  SetInitialCwnd (SENDER, m_initialCwnd);
  SetPacingStatus (SENDER, true);
  SetPaceInitialWindow (SENDER, m_paceInitialWindow);
  SetDelAckMaxCount (RECEIVER, m_delAckMaxCount);
  NS_LOG_DEBUG ("segSize: " << m_segmentSize << " ssthresh: " << m_ssThresh <<
                " paceInitialWindow: " << m_paceInitialWindow << " delAckMaxCount " << m_delAckMaxCount);
}
 
void
TcpPacingTest::RttTrace (Time oldTime, Time newTime)
{
  NS_LOG_FUNCTION (this << oldTime << newTime);
  m_tracedRtt = newTime;
  UpdateExpectedInterval ();
}
 
void
TcpPacingTest::CWndTrace (uint32_t oldValue, uint32_t newValue)
{
  NS_LOG_FUNCTION (this << oldValue << newValue);
  m_curCwnd = newValue;
  if (m_initial)
    {
      m_initial = false;
    }
  // CWndTrace () is called after Rx ()
  // Therefore, call UpdateExpectedInterval () here instead of in Rx ()
  UpdateExpectedInterval ();
}
 
void
TcpPacingTest::BytesInFlightTrace (uint32_t oldValue, uint32_t newValue)
{
  m_bytesInFlight = newValue;
}
 
void
TcpPacingTest::UpdateExpectedInterval (void)
{
  double_t factor;
  Time rtt = 2 * GetPropagationDelay ();
  if (m_curCwnd < m_ssThresh / 2)
    {
      factor = static_cast<double> (m_pacingSsRatio) / 100;
    }
  else
    {
      factor = static_cast<double> (m_pacingCaRatio) / 100;
    }
 
  if (!m_paceInitialWindow && (m_curCwnd == m_initialCwnd * m_segmentSize))
    {
      // If initial cwnd is not paced, we expect packet pacing interval to be zero
      m_expectedInterval = Seconds (0);
    }
  else
    {
      // Use the estimate according to update equation
      m_expectedInterval = Seconds ((m_segmentSize * m_tracedRtt.GetSeconds ()) / (factor * m_curCwnd));
    }
}
 
void
TcpPacingTest::Rx (const Ptr<const Packet> p, const TcpHeader &h, SocketWho who)
{
  if (who == SENDER)
    {
      uint8_t flags = h.GetFlags ();
      uint8_t hasFin = flags & TcpHeader::FIN;
      uint8_t hasAck = flags & TcpHeader::ACK;
      if (hasFin && hasAck)
        {
          m_isConnAboutToEnd = true;
          NS_LOG_DEBUG ("Sender received a FIN/ACK packet");
        }
      else
        {
          m_isConnAboutToEnd = false;
          NS_LOG_DEBUG ("Sender received an ACK packet");
        }
    }
}
 
void
TcpPacingTest::Tx (const Ptr<const Packet> p, const TcpHeader &h, SocketWho who)
{
  NS_LOG_FUNCTION (this << p << h << who);
 
  if (who == SENDER)
    {
      m_packetsSent++;
      // Start pacing checks from the second data packet onwards because
      // an interval to check does not exist for the first data packet.
      // The first two (non-data) packets correspond to SYN and an
      // empty ACK, respectively, so start checking after three packets are sent
      bool beyondInitialDataSegment = (m_packetsSent > 3);
      Time actualInterval = Simulator::Now () - m_prevTxTime;
      NS_LOG_DEBUG ("TX sent: packetsSent: " << m_packetsSent << " fullCwnd: " << m_isFullCwndSent << " nearEnd: " <<
                    m_isConnAboutToEnd << " beyondInitialDataSegment " << beyondInitialDataSegment);
      if (!m_isFullCwndSent && !m_isConnAboutToEnd && beyondInitialDataSegment)
        {
          // Consider a small error margin, and ensure that the actual and expected intervals lie within this error
          Time errorMargin = NanoSeconds (10);
          NS_TEST_ASSERT_MSG_LT_OR_EQ (std::abs ((actualInterval - m_nextPacketInterval).GetSeconds ()), errorMargin.GetSeconds (), "Packet delivery in slow start didn't match pacing rate");
          NS_LOG_DEBUG ("Pacing Check: interval (s): " << actualInterval.GetSeconds () <<
                        " expected interval (s): " << m_nextPacketInterval.GetSeconds () <<
                        " difference (s): " << std::abs ((actualInterval - m_nextPacketInterval).GetSeconds ()) <<
                        " errorMargin (s): " << errorMargin.GetSeconds ());
        }
 
      m_prevTxTime = Simulator::Now ();
      // bytesInFlight isn't updated yet. Its trace is called after Tx
      // so add an additional m_segmentSize to bytesInFlight
      uint32_t soonBytesInFlight = m_bytesInFlight + m_segmentSize;
      bool canPacketBeSent = ((m_curCwnd - soonBytesInFlight) >= m_segmentSize);
      if (!canPacketBeSent || (m_curCwnd == 0))
        {
          m_isFullCwndSent = true;
        }
      else
        {
          m_isFullCwndSent = false;
        }
      m_nextPacketInterval = m_expectedInterval;
      NS_LOG_DEBUG ("Next expected interval (s): " << m_nextPacketInterval.GetSeconds ());
    }
}
 
void
TcpPacingTest::QueueDrop (SocketWho who)
{
  NS_FATAL_ERROR ("Drop on the queue; cannot validate congestion avoidance");
}
 
void
TcpPacingTest::PhyDrop (SocketWho who)
{
  NS_FATAL_ERROR ("Drop on the phy: cannot validate congestion avoidance");
}
 
void
TcpPacingTest::NormalClose (SocketWho who)
{
  if (who == SENDER)
    {
      m_event.Cancel ();
    }
}
 
class TcpPacingTestSuite : public TestSuite
{
public:
  TcpPacingTestSuite () : TestSuite ("tcp-pacing-test", UNIT)
  {
    uint16_t pacingSsRatio = 200;
    uint16_t pacingCaRatio = 120;
    uint32_t segmentSize = 1000;
    uint32_t packetSize = 1000;
    uint32_t numPackets = 40;
    uint32_t delAckMaxCount = 1;
    TypeId tid = TcpNewReno::GetTypeId ();
    uint32_t ssThresh = 1e9; // default large value
    bool paceInitialWindow = false;
    std::string description;
 
    description = std::string ("Pacing case 1: Slow start only, no initial pacing");
    AddTestCase (new TcpPacingTest (segmentSize, packetSize, numPackets, pacingSsRatio, pacingCaRatio, ssThresh, paceInitialWindow, delAckMaxCount, tid, description), TestCase::QUICK);
 
    paceInitialWindow = true;
    description = std::string ("Pacing case 2: Slow start only, initial pacing");
    AddTestCase (new TcpPacingTest (segmentSize, packetSize, numPackets, pacingSsRatio, pacingCaRatio, ssThresh, paceInitialWindow, delAckMaxCount, tid, description), TestCase::QUICK);
 
    // set ssThresh to some smaller value to check that pacing
    // slows down in second half of slow start, then transitions to CA
    description = std::string ("Pacing case 3: Slow start, followed by transition to Congestion avoidance, no initial pacing");
    paceInitialWindow = false;
    ssThresh = 40;
    numPackets = 60;
    AddTestCase (new TcpPacingTest (segmentSize, packetSize, numPackets, pacingSsRatio, pacingCaRatio, ssThresh, paceInitialWindow, delAckMaxCount, tid, description), TestCase::QUICK);
 
    // Repeat tests, but with more typical delAckMaxCount == 2
    delAckMaxCount = 2;
    paceInitialWindow = false;
    ssThresh = 1e9;
    numPackets = 40;
    description = std::string ("Pacing case 4: Slow start only, no initial pacing, delayed ACKs");
    AddTestCase (new TcpPacingTest (segmentSize, packetSize, numPackets, pacingSsRatio, pacingCaRatio, ssThresh, paceInitialWindow, delAckMaxCount, tid, description), TestCase::QUICK);
 
    paceInitialWindow = true;
    description = std::string ("Pacing case 5: Slow start only, initial pacing, delayed ACKs");
    AddTestCase (new TcpPacingTest (segmentSize, packetSize, numPackets, pacingSsRatio, pacingCaRatio, ssThresh, paceInitialWindow, delAckMaxCount, tid, description), TestCase::QUICK);
 
    description = std::string ("Pacing case 6: Slow start, followed by transition to Congestion avoidance, no initial pacing, delayed ACKs");
    paceInitialWindow = false;
    ssThresh = 40;
    numPackets = 60;
    AddTestCase (new TcpPacingTest (segmentSize, packetSize, numPackets, pacingSsRatio, pacingCaRatio, ssThresh, paceInitialWindow, delAckMaxCount, tid, description), TestCase::QUICK);
  }
};
 
static TcpPacingTestSuite g_tcpPacingTest;