| /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */ |
| /* |
| * Copyright (C) 2016-2018, Arizona Board of Regents. |
| * |
| * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions). |
| * |
| * ndn-cxx library is free software: you can redistribute it and/or modify it under the |
| * terms of the GNU Lesser General Public License as published by the Free Software |
| * Foundation, either version 3 of the License, or (at your option) any later version. |
| * |
| * ndn-cxx library 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 Lesser General Public License for more details. |
| * |
| * You should have received copies of the GNU General Public License and GNU Lesser |
| * General Public License along with ndn-cxx, 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 |
| * @author Chavoosh Ghasemi |
| */ |
| |
| #ifndef NDN_CXX_UTIL_RTT_ESTIMATOR_HPP |
| #define NDN_CXX_UTIL_RTT_ESTIMATOR_HPP |
| |
| #include "../common.hpp" |
| #include "signal.hpp" |
| #include "time.hpp" |
| |
| namespace ndn { |
| namespace util { |
| |
| /** |
| * @brief RTT Estimator. |
| * |
| * This class implements the "Mean-Deviation" RTT estimator, as discussed in RFC 6298, |
| * with the modifications to RTO calculation described in RFC 7323 Appendix G. |
| */ |
| class RttEstimator |
| { |
| public: |
| using MillisecondsDouble = time::duration<double, time::milliseconds::period>; |
| |
| public: |
| class Options |
| { |
| public: |
| constexpr |
| Options() noexcept |
| { |
| } |
| |
| public: |
| double alpha = 0.125; ///< weight of exponential moving average for meanRtt |
| double beta = 0.25; ///< weight of exponential moving average for varRtt |
| int k = 4; ///< factor of RTT variation when calculating RTO |
| MillisecondsDouble initialRto = MillisecondsDouble(1000.0); ///< initial RTO value |
| MillisecondsDouble minRto = MillisecondsDouble(200.0); ///< lower bound of RTO |
| MillisecondsDouble maxRto = MillisecondsDouble(20000.0); ///< upper bound of RTO |
| int rtoBackoffMultiplier = 2; |
| }; |
| |
| /** |
| * @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. |
| * |
| * @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. |
| * @note Don't add RTT measurements for retransmissions |
| */ |
| void |
| addMeasurement(MillisecondsDouble rtt, size_t nExpectedSamples); |
| |
| /** |
| * @brief Returns the estimated RTO value |
| */ |
| MillisecondsDouble |
| getEstimatedRto() const |
| { |
| return m_rto; |
| } |
| |
| /** |
| * @brief Returns the minimum RTT observed |
| */ |
| MillisecondsDouble |
| getMinRtt() const |
| { |
| return m_rttMin; |
| } |
| |
| /** |
| * @brief Returns the maximum RTT observed |
| */ |
| MillisecondsDouble |
| getMaxRtt() const |
| { |
| return m_rttMax; |
| } |
| |
| /** |
| * @brief Returns the average RTT |
| */ |
| MillisecondsDouble |
| getAvgRtt() const |
| { |
| return m_rttAvg; |
| } |
| |
| /** |
| * @brief Backoff RTO by a factor of Options::rtoBackoffMultiplier |
| */ |
| void |
| backoffRto(); |
| |
| private: |
| const Options m_options; |
| MillisecondsDouble m_sRtt; ///< smoothed round-trip time |
| MillisecondsDouble m_rttVar; ///< round-trip time variation |
| MillisecondsDouble m_rto; ///< retransmission timeout |
| MillisecondsDouble m_rttMin; |
| MillisecondsDouble m_rttMax; |
| MillisecondsDouble m_rttAvg; |
| int64_t m_nRttSamples; ///< number of RTT samples |
| }; |
| |
| } // namespace util |
| } // namespace ndn |
| |
| #endif // NDN_CXX_UTIL_RTT_ESTIMATOR_HPP |