diff --git a/tools/chunks/catchunks/aimd-rtt-estimator.hpp b/tools/chunks/catchunks/aimd-rtt-estimator.hpp
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+++ b/tools/chunks/catchunks/aimd-rtt-estimator.hpp
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+/**
+ * Copyright (c) 2016,  Arizona Board of Regents.
+ *
+ * This file is part of ndn-tools (Named Data Networking Essential Tools).
+ * See AUTHORS.md for complete list of ndn-tools authors and contributors.
+ *
+ * ndn-tools is free software: you can redistribute it and/or modify it under the terms
+ * of the GNU General Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later version.
+ *
+ * ndn-tools 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
+ * ndn-tools, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
+ *
+ * @author Shuo Yang
+ * @author Weiwei Liu
+ */
+
+#ifndef NDN_TOOLS_CHUNKS_CATCHUNKS_AIMD_RTT_ESTIMATOR_HPP
+#define NDN_TOOLS_CHUNKS_CATCHUNKS_AIMD_RTT_ESTIMATOR_HPP
+
+#include "core/common.hpp"
+
+namespace ndn {
+namespace chunks {
+namespace aimd {
+
+typedef time::duration<double, time::milliseconds::period> Milliseconds;
+
+struct RttRtoSample
+{
+  uint64_t segNo;
+  Milliseconds rtt; ///< measured RTT
+  Milliseconds sRtt; ///< smoothed RTT
+  Milliseconds rttVar; ///< RTT variation
+  Milliseconds rto; ///< retransmission timeout
+};
+
+/**
+ * @brief RTT Estimator.
+ *
+ * This class implements the "Mean--Deviation" RTT estimator, as discussed in RFC6298,
+ * with the modifications to RTO calculation described in RFC 7323 Appendix G.
+ */
+class RttEstimator
+{
+public:
+  class Options
+  {
+  public:
+    Options()
+      : isVerbose(false)
+      , alpha(0.125)
+      , beta(0.25)
+      , k(4)
+      , initialRto(1000.0)
+      , minRto(200.0)
+      , maxRto(20000.0)
+      , rtoBackoffMultiplier(2)
+    {
+    }
+
+  public:
+    bool isVerbose;
+    double alpha; ///< parameter for RTT estimation
+    double beta; ///< parameter for RTT variation calculation
+    int k; ///< factor of RTT variation when calculating RTO
+    Milliseconds initialRto; ///< initial RTO value
+    Milliseconds minRto; ///< lower bound of RTO
+    Milliseconds maxRto; ///< upper bound of RTO
+    int rtoBackoffMultiplier;
+  };
+
+  /**
+   * @brief create a RTT Estimator
+   *
+   * Configures the RTT Estimator with the default parameters if an instance of Options
+   * is not passed to the constructor.
+   */
+  explicit
+  RttEstimator(const Options& options = Options());
+
+  /**
+   * @brief Add a new RTT measurement to the estimator for the given received segment.
+   *
+   * @note Don't take RTT measurement for retransmitted segments
+   * @param segNo the segment number of the received segmented Data
+   * @param rtt the sampled rtt
+   * @param nExpectedSamples number of expected samples, must be greater than 0.
+   *        It should be set to current number of in-flight Interests. Please
+   *        refer to Appendix G of RFC 7323 for details.
+   */
+  void
+  addMeasurement(uint64_t segNo, Milliseconds rtt, size_t nExpectedSamples);
+
+  /**
+   * @return estimated RTO
+   */
+  Milliseconds
+  getEstimatedRto() const;
+
+  /**
+   * @brief backoff RTO by the factor of RttEstimatorOptions::rtoBackoffMultiplier
+   */
+  void
+  backoffRto();
+
+  /**
+   * @brief Signals after rtt is measured
+   */
+  signal::Signal<RttEstimator, RttRtoSample> afterRttMeasurement;
+
+PUBLIC_WITH_TESTS_ELSE_PRIVATE:
+  const Options m_options;
+  Milliseconds m_sRtt; ///< smoothed round-trip time
+  Milliseconds m_rttVar; ///< round-trip time variation
+  Milliseconds m_rto; ///< retransmission timeout
+};
+
+/**
+ * @brief returns the estimated RTO value
+ */
+inline Milliseconds
+RttEstimator::getEstimatedRto() const
+{
+  return m_rto;
+}
+
+std::ostream&
+operator<<(std::ostream& os, const RttEstimator::Options& options);
+
+} // namespace aimd
+} // namespace chunks
+} // namespace ndn
+
+#endif // NDN_TOOLS_CHUNKS_CATCHUNKS_RTT_ESTIMATOR_HPP