| Junxiao Shi | 02e3224 | 2014-05-17 20:51:11 -0700 | [diff] [blame] | 1 | /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */ |
| 2 | /** |
| 3 | * Copyright (c) 2014 Regents of the University of California, |
| 4 | * Arizona Board of Regents, |
| 5 | * Colorado State University, |
| 6 | * University Pierre & Marie Curie, Sorbonne University, |
| 7 | * Washington University in St. Louis, |
| 8 | * Beijing Institute of Technology, |
| 9 | * The University of Memphis |
| 10 | * |
| 11 | * This file is part of NFD (Named Data Networking Forwarding Daemon). |
| 12 | * See AUTHORS.md for complete list of NFD authors and contributors. |
| 13 | * |
| 14 | * NFD is free software: you can redistribute it and/or modify it under the terms |
| 15 | * of the GNU General Public License as published by the Free Software Foundation, |
| 16 | * either version 3 of the License, or (at your option) any later version. |
| 17 | * |
| 18 | * NFD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; |
| 19 | * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR |
| 20 | * PURPOSE. See the GNU General Public License for more details. |
| 21 | * |
| 22 | * You should have received a copy of the GNU General Public License along with |
| 23 | * NFD, e.g., in COPYING.md file. If not, see <http://www.gnu.org/licenses/>. |
| 24 | **/ |
| 25 | |
| 26 | #include "rtt-estimator.hpp" |
| 27 | |
| 28 | namespace nfd { |
| 29 | |
| 30 | RttEstimator::RttEstimator(uint16_t maxMultiplier, Duration minRto, double gain) |
| 31 | : m_maxMultiplier(maxMultiplier) |
| 32 | , m_minRto(minRto.count()) |
| 33 | , m_rtt(RttEstimator::getInitialRtt().count()) |
| 34 | , m_gain(gain) |
| 35 | , m_variance(0) |
| 36 | , m_multiplier(1) |
| 37 | , m_nSamples(0) |
| 38 | { |
| 39 | } |
| 40 | |
| 41 | void |
| 42 | RttEstimator::addMeasurement(Duration measure) |
| 43 | { |
| 44 | double m = static_cast<double>(measure.count()); |
| 45 | if (m_nSamples > 0) { |
| 46 | double err = m - m_rtt; |
| 47 | double gErr = err * m_gain; |
| 48 | m_rtt += gErr; |
| 49 | double difference = std::abs(err) - m_variance; |
| 50 | m_variance += difference * m_gain; |
| 51 | } else { |
| 52 | m_rtt = m; |
| 53 | m_variance = m; |
| 54 | } |
| 55 | ++m_nSamples; |
| 56 | m_multiplier = 1; |
| 57 | } |
| 58 | |
| 59 | void |
| 60 | RttEstimator::incrementMultiplier() |
| 61 | { |
| 62 | m_multiplier = std::min(static_cast<uint16_t>(m_multiplier + 1), m_maxMultiplier); |
| 63 | } |
| 64 | |
| 65 | void |
| 66 | RttEstimator::doubleMultiplier() |
| 67 | { |
| 68 | m_multiplier = std::min(static_cast<uint16_t>(m_multiplier * 2), m_maxMultiplier); |
| 69 | } |
| 70 | |
| 71 | RttEstimator::Duration |
| 72 | RttEstimator::computeRto() const |
| 73 | { |
| 74 | double rto = std::max(m_minRto, m_rtt + 4 * m_variance); |
| 75 | rto *= m_multiplier; |
| 76 | return Duration(static_cast<Duration::rep>(rto)); |
| 77 | } |
| 78 | |
| 79 | } // namespace nfd |