/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */

/*

 * Copyright (c) 2011 Adrian Sai-wah Tam

 *

 * 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: Adrian Sai-wah Tam <adrian.sw.tam@gmail.com>

 * Documentation, test cases: Natale Patriciello <natale.patriciello@gmail.com>

 */

#ifndef TCP_OPTION_WINSCALE_H

#define TCP_OPTION_WINSCALE_H

#include "tcp-option.h"

namespace ns3 {

/**

 * \brief Defines the TCP option of kind 3 (window scale option) as in \RFC{1323}

 *

 * For more efficient use of high bandwidth networks, a larger TCP window size

 * may be used. The TCP window size field controls the flow of data and its

 * value is limited to between 2 and 65,535 bytes.

 *

 * Since the size field cannot be expanded, a scaling factor is used.

 * The TCP window scale option, as defined in \RFC{1323}, is an option used

 * to increase the maximum window size from 65,535 bytes to 1 gigabyte.

 * Scaling up to larger window sizes is a part of what is necessary for TCP Tuning.

 *

 * The window scale option is used only during the TCP 3-way handshake.

 * The window scale value represents the number of bits to left-shift the

 * 16-bit window size field. The window scale value can be set from 0

 * (no shift) to 14 for each direction independently. Both sides must

 * send the option in their SYN segments to enable window scaling in

 * either direction.

 */

class TcpOptionWinScale : public TcpOption

{

public:

  /**

   * \brief Get the type ID.

   * \return the object TypeId

   */

  static TypeId GetTypeId (void);

  virtual TypeId GetInstanceTypeId (void) const;

  TcpOptionWinScale ();

  virtual ~TcpOptionWinScale ();

  virtual void Print (std::ostream &os) const;

  virtual void Serialize (Buffer::Iterator start) const;

  virtual uint32_t Deserialize (Buffer::Iterator start);

  virtual uint8_t GetKind (void) const;

  virtual uint32_t GetSerializedSize (void) const;

  /**

   * \brief Get the scale value (uint8_t)

   * \return The scale value

   */

  uint8_t GetScale (void) const;

  /**

   * \brief Set the scale option

   *

   * The scale option SHOULD be <= 14 (as \RFC{1323}).

   *

   * \param scale Scale factor

   */

  void SetScale (uint8_t scale);

protected:

  uint8_t m_scale; //!< Window scaling in number of bit shift

};

} // namespace ns3

#endif /* TCP_OPTION_WINSCALE */