/* -*- 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>,

 * and 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.

 */

#ifndef TCP_WESTWOOD_H

#define TCP_WESTWOOD_H

#include "tcp-socket-base.h"

#include "ns3/packet.h"

namespace ns3 {

/**

 * \ingroup socket

 * \ingroup tcp

 *

 * \brief An implementation of a stream socket using TCP.

 *

 * This class contains the implementation of TCP Westwood and Westwood+.

 *

 * Westwood and Westwood+ employ the AIAD (Additive Increase/Adaptive Decrease) 

 * congestion control paradigm. When a congestion episode happens, 

 * instead of halving the cwnd, these protocols try to estimate the network's

 * bandwidth and use the estimated value to adjust the cwnd. 

 * While Westwood performs the bandwidth sampling every ACK reception, 

 * Westwood+ samples the bandwidth every RTT.

 *

 * The two main methods in the implementation are the CountAck (const TCPHeader&)

 * and the EstimateBW (int, const, Time). The CountAck method calculates

 * the number of acknowledged segments on the receipt of an ACK.

 * The EstimateBW estimates the bandwidth based on the value returned by CountAck

 * and the sampling interval (last ACK inter-arrival time for Westwood and last RTT for Westwood+).   

 */

class TcpWestwood : public TcpSocketBase

{

public:

  /**

   * \brief Get the type ID.

   * \return the object TypeId

   */

  static TypeId GetTypeId (void);

  TcpWestwood (void);

  /**

   * \brief Copy constructor

   * \param sock the object to copy

   */

  TcpWestwood (const TcpWestwood& sock);

  virtual ~TcpWestwood (void);

  /**

   * \brief Protocol variant (Westwood or Westwood+)

   */

  enum ProtocolType 

  {

    WESTWOOD,

    WESTWOODPLUS

  };

  /**

   * \brief Filter type (None or Tustin)

   */

  enum FilterType 

  {

    NONE,

    TUSTIN

  };

protected:

  virtual Ptr<TcpSocketBase> Fork (void); // Call CopyObject<TcpTahoe> to clone me

  virtual void NewAck (SequenceNumber32 const& seq); // Inc cwnd and call NewAck() of parent

  virtual void DupAck (const TcpHeader& t, uint32_t count);  // Treat 3 dupack as timeout

  virtual void Retransmit (void); // Retransmit time out

  /**

   * Process the newly received ACK

   *

   * \param packet the received ACK packet

   * \param tcpHeader the header attached to the ACK packet

   */  

  virtual void ReceivedAck (Ptr<Packet> packet, const TcpHeader& tcpHeader);

  /**

   * Estimate the RTT, record the minimum value,

   * and run a clock on the RTT to trigger Westwood+ bandwidth sampling

   * \param header the packet header

   */

  virtual void EstimateRtt (const TcpHeader& header);

private:

  /**

   * Calculate the number of acknowledged packets upon the receipt of an ACK packet

   *

   * \param tcpHeader the header of the received ACK packet

   * \return the number of ACKed packets

   */

  int CountAck (const TcpHeader& tcpHeader);

  /**

   * Update the total number of acknowledged packets during the current RTT

   *

   * \param acked the number of packets the currently received ACK acknowledges

   */

  void UpdateAckedSegments (int acked);

  /**

   * Estimate the network's bandwidth

   *

   * \param acked the number of acknowledged packets returned by CountAck

   * \param tcpHeader the header of the packet

   * \param rtt the RTT estimation

   */

  void EstimateBW (int acked, const TcpHeader& tcpHeader, Time rtt);

  /**

   * Tustin filter

   */

  void Filtering (void);

protected:

  bool                   m_inFastRec;              //!< Currently in fast recovery if TRUE

  TracedValue<double>    m_currentBW;              //!< Current value of the estimated BW

  double                 m_lastSampleBW;           //!< Last bandwidth sample

  double                 m_lastBW;                 //!< Last bandwidth sample after being filtered

  Time                   m_minRtt;                 //!< Minimum RTT

  double                 m_lastAck;                //!< The time last ACK was received

  SequenceNumber32       m_prevAckNo;              //!< Previously received ACK number

  int                    m_accountedFor;           //!< The number of received DUPACKs

  enum ProtocolType      m_pType;                  //!< 0 for Westwood, 1 for Westwood+

  enum FilterType        m_fType;                  //!< 0 for none, 1 for Tustin

  int                    m_ackedSegments;          //!< The number of segments ACKed between RTTs

  bool                   m_IsCount;                //!< Start keeping track of m_ackedSegments for Westwood+ if TRUE

  EventId                m_bwEstimateEvent;        //!< The BW estimation event for Westwood+

};

} // namespace ns3

#endif /* TCP_WESTWOOD_H */