libns3-dev 3.26+dfsg-1 / usr / include / ns3.26 / ns3 / tcp-veno.h

/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2016 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
 *
 * Author: Truc Anh N. Nguyen <annguyen@ittc.ku.edu>
 *
 * 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.
 */

#ifndef TCPVENO_H
#define TCPVENO_H

#include "ns3/tcp-congestion-ops.h"

namespace ns3 {

/**
 * \ingroup congestionOps
 *
 * \brief An implementation of TCP Veno
 *
 * TCP Veno enhances Reno algorithm for more effectively dealing with random
 * packet loss in wireless access networks by employing Vegas's method in
 * estimating the backlog at the bottleneck queue to distinguish between
 * congestive and non-congestive states.
 *
 * The backlog (the number of packets accumulated at the bottleneck queue) is
 * calculated using Equation (1):
 *
 *         N = Actual * (RTT - BaseRTT) = Diff * BaseRTT        (1)
 * where
 *         Diff = Expected - Actual = cwnd/BaseRTT - cwnd/RTT
 *
 * Veno makes decision on cwnd modification based on the calculated N and its
 * predefined threshold beta.
 *
 * Specifically, it refines the additive increase algorithm of Reno so that the
 * connection can stay longer in the stable state by incrementing cwnd by
 * 1/cwnd for every other new ACK received after the available bandwidth has
 * been fully utilized, i.e. when N exceeds beta.  Otherwise, Veno increases
 * its cwnd by 1/cwnd upon every new ACK receipt as in Reno.
 *
 * In the multiplicative decrease algorithm, when Veno is in the non-congestive
 * state, i.e. when N is less than beta, Veno decrements its cwnd by only 1/5
 * because the loss encountered is more likely a corruption-based loss than a
 * congestion-based.  Only when N is greater than beta, Veno halves its sending
 * rate as in Reno.
 *
 * More information: http://dx.doi.org/10.1109/JSAC.2002.807336
 */

class TcpVeno : public TcpNewReno
{
public:
  /**
   * \brief Get the type ID.
   * \return the object TypeId
   */
  static TypeId GetTypeId (void);

  /**
   * Create an unbound tcp socket.
   */
  TcpVeno (void);

  /**
   * \brief Copy constructor
   * \param sock the object to copy
   */
  TcpVeno (const TcpVeno& sock);
  virtual ~TcpVeno (void);

  virtual std::string GetName () const;

  /**
   * \brief Perform RTT sampling needed to execute Veno algorithm
   *
   * The function filters RTT samples from the last RTT to find
   * the current smallest propagation delay + queueing delay (m_minRtt).
   * We take the minimum to avoid the effects of delayed ACKs.
   *
   * The function also min-filters all RTT measurements seen to find the
   * propagation delay (m_baseRtt).
   *
   * \param tcb internal congestion state
   * \param segmentsAcked count of segments ACKed
   * \param rtt last RTT
   *
   */
  virtual void PktsAcked (Ptr<TcpSocketState> tcb, uint32_t segmentsAcked,
                          const Time& rtt);

  /**
   * \brief Enable/disable Veno depending on the congestion state
   *
   * We only start a Veno when we are in normal congestion state (CA_OPEN state).
   *
   * \param tcb internal congestion state
   * \param newState new congestion state to which the TCP is going to switch
   */
  virtual void CongestionStateSet (Ptr<TcpSocketState> tcb,
                                   const TcpSocketState::TcpCongState_t newState);

  /**
   * \brief Adjust cwnd following Veno additive increase algorithm
   *
   * \param tcb internal congestion state
   * \param segmentsAcked count of segments ACKed
   */
  virtual void IncreaseWindow (Ptr<TcpSocketState> tcb, uint32_t segmentsAcked);

  /**
   * \brief Get slow start threshold during Veno multiplicative-decrease phase
   *
   * \param tcb internal congestion state
   * \param bytesInFlight bytes in flight
   *
   * \return the slow start threshold value
   */
  virtual uint32_t GetSsThresh (Ptr<const TcpSocketState> tcb,
                                uint32_t bytesInFlight);

  virtual Ptr<TcpCongestionOps> Fork ();

protected:
private:
  /**
   * \brief Enable Veno algorithm to start Veno sampling
   *
   * Veno algorithm is enabled in the following situations:
   * 1. at the establishment of a connection
   * 2. after an RTO
   * 3. after fast recovery
   * 4. when an idle connection is restarted
   *
   */
  void EnableVeno ();

  /**
   * \brief Turn off Veno
   */
  void DisableVeno ();

private:
  Time m_baseRtt;                    //!< Minimum of all RTT measurements seen during connection
  Time m_minRtt;                     //!< Minimum of RTTs measured within last RTT
  uint32_t m_cntRtt;                 //!< Number of RTT measurements during last RTT
  bool m_doingVenoNow;               //!< If true, do Veno for this RTT
  uint32_t m_diff;                   //!< Difference between expected and actual throughput
  bool m_inc;                        //!< If true, cwnd needs to be incremented
  uint32_t m_ackCnt;                 //!< Number of received ACK
  uint32_t m_beta;                   //!< Threshold for congestion detection
};

} // namespace ns3

#endif // TCPVENO_H