tcp-westwood.cc

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/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2013 ResiliNets, ITTC, University of Kansas 
 *
 * 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: Siddharth Gangadhar <siddharth@ittc.ku.edu>,
 *          Truc Anh N. Nguyen <annguyen@ittc.ku.edu>,
 *          Greeshma Umapathi
 *
 * James P.G. Sterbenz <jpgs@ittc.ku.edu>, director
 * ResiliNets Research Group  http://wiki.ittc.ku.edu/resilinets
 * Information and Telecommunication Technology Center (ITTC)
 * and Department of Electrical Engineering and Computer Science
 * The University of Kansas Lawrence, KS USA.
 *
 * Work supported in part by NSF FIND (Future Internet Design) Program
 * under grant CNS-0626918 (Postmodern Internet Architecture),
 * NSF grant CNS-1050226 (Multilayer Network Resilience Analysis and Experimentation on GENI),
 * US Department of Defense (DoD), and ITTC at The University of Kansas.
 */
 
#include "tcp-westwood.h"
#include "ns3/log.h"
#include "ns3/simulator.h"
#include "rtt-estimator.h"
#include "tcp-socket-base.h"
 
NS_LOG_COMPONENT_DEFINE ("TcpWestwood");
 
namespace ns3 {
 
NS_OBJECT_ENSURE_REGISTERED (TcpWestwood);
 
TypeId
TcpWestwood::GetTypeId (void)
{
  static TypeId tid = TypeId("ns3::TcpWestwood")
    .SetParent<TcpNewReno>()
    .SetGroupName ("Internet")
    .AddConstructor<TcpWestwood>()
    .AddAttribute("FilterType", "Use this to choose no filter or Tustin's approximation filter",
                  EnumValue(TcpWestwood::TUSTIN), MakeEnumAccessor(&TcpWestwood::m_fType),
                  MakeEnumChecker(TcpWestwood::NONE, "None", TcpWestwood::TUSTIN, "Tustin"))
    .AddAttribute("ProtocolType", "Use this to let the code run as Westwood or WestwoodPlus",
                  EnumValue(TcpWestwood::WESTWOOD),
                  MakeEnumAccessor(&TcpWestwood::m_pType),
                  MakeEnumChecker(TcpWestwood::WESTWOOD, "Westwood",TcpWestwood::WESTWOODPLUS, "WestwoodPlus"))
    .AddTraceSource("EstimatedBW", "The estimated bandwidth",
                    MakeTraceSourceAccessor(&TcpWestwood::m_currentBW),
                    "ns3::TracedValueCallback::DataRate")
  ;
  return tid;
}
 
TcpWestwood::TcpWestwood (void) :
  TcpNewReno (),
  m_currentBW (0),
  m_lastSampleBW (0),
  m_lastBW (0),
  m_ackedSegments (0),
  m_IsCount (false),
  m_lastAck (0)
{
  NS_LOG_FUNCTION (this);
}
 
TcpWestwood::TcpWestwood (const TcpWestwood& sock) :
  TcpNewReno (sock),
  m_currentBW (sock.m_currentBW),
  m_lastSampleBW (sock.m_lastSampleBW),
  m_lastBW (sock.m_lastBW),
  m_pType (sock.m_pType),
  m_fType (sock.m_fType),
  m_IsCount (sock.m_IsCount)
{
  NS_LOG_FUNCTION (this);
  NS_LOG_LOGIC ("Invoked the copy constructor");
}
 
TcpWestwood::~TcpWestwood (void)
{
}
 
void
TcpWestwood::PktsAcked (Ptr<TcpSocketState> tcb, uint32_t packetsAcked,
                        const Time& rtt)
{
  NS_LOG_FUNCTION (this << tcb << packetsAcked << rtt);
 
  if (rtt.IsZero ())
    {
      NS_LOG_WARN ("RTT measured is zero!");
      return;
    }
 
  m_ackedSegments += packetsAcked;
 
  if (m_pType == TcpWestwood::WESTWOOD)
    {
      EstimateBW (rtt, tcb);
    }
  else if (m_pType == TcpWestwood::WESTWOODPLUS)
    {
      if (!(rtt.IsZero () || m_IsCount))
        {
          m_IsCount = true;
          m_bwEstimateEvent.Cancel ();
          m_bwEstimateEvent = Simulator::Schedule (rtt, &TcpWestwood::EstimateBW,
                                                   this, rtt, tcb);
        }
    }
}
 
void
TcpWestwood::EstimateBW (const Time &rtt, Ptr<TcpSocketState> tcb)
{
  NS_LOG_FUNCTION (this);
 
  NS_ASSERT (!rtt.IsZero ());
 
  if (m_pType == TcpWestwood::WESTWOOD)
    {
      Time currentAck = Simulator::Now ();
 
      NS_ABORT_MSG_IF (currentAck == m_lastAck,
        "This violates a model assumption and would lead to divide-by-zero; please report to ns-3 maintainers if this occurs.");
 
      m_currentBW = DataRate (m_ackedSegments * tcb->m_segmentSize * 8.0 / (currentAck - m_lastAck).GetSeconds ());
      m_lastAck = currentAck;
    }
  else if (m_pType == TcpWestwood::WESTWOODPLUS)
    {
      m_currentBW = DataRate (m_ackedSegments * tcb->m_segmentSize * 8.0 / rtt.GetSeconds ());
      m_IsCount = false;
    }
 
  m_ackedSegments = 0;
 
  NS_LOG_LOGIC ("Estimated BW: " << m_currentBW);
 
  // Filter the BW sample
 
  constexpr double alpha = 0.9;
 
  if (m_fType == TcpWestwood::TUSTIN)
    {
      DataRate sample_bwe = m_currentBW;
      m_currentBW = (m_lastBW * alpha) + (((sample_bwe + m_lastSampleBW) * 0.5) * (1 - alpha));
      m_lastSampleBW = sample_bwe;
      m_lastBW = m_currentBW;
    }
 
  NS_LOG_LOGIC ("Estimated BW after filtering: " << m_currentBW);
}
 
uint32_t
TcpWestwood::GetSsThresh (Ptr<const TcpSocketState> tcb,
                          [[maybe_unused]] uint32_t bytesInFlight)
{
  uint32_t ssThresh = static_cast<uint32_t> ((m_currentBW * tcb->m_minRtt) / 8.0);
 
  NS_LOG_LOGIC ("CurrentBW: " << m_currentBW <<
                " minRtt: " << tcb->m_minRtt <<
                " ssThresh: " << ssThresh);
 
  return std::max (2 * tcb->m_segmentSize, ssThresh);
}
 
Ptr<TcpCongestionOps>
TcpWestwood::Fork ()
{
  return CreateObject<TcpWestwood> (*this);
}
 
} // namespace ns3