diff --git a/utils/ndn-rtt-estimator.h b/utils/ndn-rtt-estimator.h
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+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+//
+// Copyright (c) 2006 Georgia Tech Research Corporation
+//
+// 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: Rajib Bhattacharjea<raj.b@gatech.edu>
+//
+
+// Georgia Tech Network Simulator - Round Trip Time Estimation Class
+// George F. Riley.  Georgia Tech, Spring 2002
+
+// THIS IS A COPY OF rtt-estimator.h from internet module with minor modifications
+
+#ifndef NDN_RTT_ESTIMATOR_H
+#define NDN_RTT_ESTIMATOR_H
+
+#include <deque>
+#include "ns3/sequence-number.h"
+#include "ns3/nstime.h"
+#include "ns3/object.h"
+
+namespace ns3 {
+
+namespace ndn {
+
+/**
+ * \ingroup tcp
+ *
+ * \brief Helper class to store RTT measurements
+ */
+class RttHistory {
+public:
+  RttHistory (SequenceNumber32 s, uint32_t c, Time t);
+  RttHistory (const RttHistory& h); // Copy constructor
+public:
+  SequenceNumber32  seq;  // First sequence number in packet sent
+  uint32_t        count;  // Number of bytes sent
+  Time            time;   // Time this one was sent
+  bool            retx;   // True if this has been retransmitted
+};
+
+typedef std::deque<RttHistory> RttHistory_t;
+
+/**
+ * \ingroup tcp
+ *
+ * \brief Base class for all RTT Estimators
+ */
+class RttEstimator : public Object {
+public:
+  static TypeId GetTypeId (void);
+
+  RttEstimator();
+  RttEstimator (const RttEstimator&);
+
+  virtual ~RttEstimator();
+
+  /**
+   * \brief Note that a particular sequence has been sent
+   * \param seq the packet sequence number.
+   * \param size the packet size.
+   */
+  virtual void SentSeq (SequenceNumber32 seq, uint32_t size);
+
+  /**
+   * \brief Note that a particular ack sequence has been received
+   * \param ackSeq the ack sequence number.
+   * \return The measured RTT for this ack.
+   */
+  virtual Time AckSeq (SequenceNumber32 ackSeq);
+
+  /**
+   * \brief Clear all history entries
+   */
+  virtual void ClearSent ();
+
+  /**
+   * \brief Add a new measurement to the estimator. Pure virtual function.
+   * \param t the new RTT measure.
+   */
+  virtual void  Measurement (Time t) = 0;
+
+  /**
+   * \brief Returns the estimated RTO. Pure virtual function.
+   * \return the estimated RTO.
+   */
+  virtual Time RetransmitTimeout () = 0;
+
+  virtual Ptr<RttEstimator> Copy () const = 0;
+
+  /**
+   * \brief Increase the estimation multiplier up to MaxMultiplier.
+   */
+  virtual void IncreaseMultiplier ();
+
+  /**
+   * \brief Resets the estimation multiplier to 1.
+   */
+  virtual void ResetMultiplier ();
+
+  /**
+   * \brief Resets the estimation to its initial state.
+   */
+  virtual void Reset ();
+
+  /**
+   * \brief Sets the Minimum RTO.
+   * \param minRto The minimum RTO returned by the estimator.
+   */
+  void SetMinRto (Time minRto);
+
+  /**
+   * \brief Get the Minimum RTO.
+   * \return The minimum RTO returned by the estimator.
+   */
+  Time GetMinRto (void) const;
+
+  /**
+   * \brief Sets the Maximum RTO.
+   * \param minRto The maximum RTO returned by the estimator.
+   */
+  void SetMaxRto (Time maxRto);
+
+  /**
+   * \brief Get the Maximum RTO.
+   * \return The maximum RTO returned by the estimator.
+   */
+  Time GetMaxRto (void) const;
+
+  /**
+   * \brief Sets the current RTT estimate (forcefully).
+   * \param estimate The current RTT estimate.
+   */
+  void SetCurrentEstimate (Time estimate);
+
+  /**
+   * \brief gets the current RTT estimate.
+   * \return The current RTT estimate.
+   */
+  Time GetCurrentEstimate (void) const;
+
+private:
+  SequenceNumber32 m_next;    // Next expected sequence to be sent
+  uint16_t m_maxMultiplier;
+  Time m_initialEstimatedRtt;
+
+protected:
+  Time         m_currentEstimatedRtt;     // Current estimate
+  Time         m_minRto;                  // minimum value of the timeout
+  Time         m_maxRto;                  // maximum value of the timeout
+  uint32_t     m_nSamples;                // Number of samples
+  uint16_t     m_multiplier;              // RTO Multiplier
+  RttHistory_t m_history;     // List of sent packet
+};
+
+} // namespace ndn
+
+} // namespace ns3
+
+#endif /* RTT_ESTIMATOR_H */