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aimd_rate_control.h (5166B)

      1 /*
      2 *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
      3 *
      4 *  Use of this source code is governed by a BSD-style license
      5 *  that can be found in the LICENSE file in the root of the source
      6 *  tree. An additional intellectual property rights grant can be found
      7 *  in the file PATENTS.  All contributing project authors may
      8 *  be found in the AUTHORS file in the root of the source tree.
      9 */
     10 
     11 #ifndef MODULES_REMOTE_BITRATE_ESTIMATOR_AIMD_RATE_CONTROL_H_
     12 #define MODULES_REMOTE_BITRATE_ESTIMATOR_AIMD_RATE_CONTROL_H_
     13 
     14 #include <stdint.h>
     15 
     16 #include <optional>
     17 
     18 #include "api/field_trials_view.h"
     19 #include "api/transport/network_types.h"
     20 #include "api/units/data_rate.h"
     21 #include "api/units/time_delta.h"
     22 #include "api/units/timestamp.h"
     23 #include "modules/congestion_controller/goog_cc/link_capacity_estimator.h"
     24 #include "modules/remote_bitrate_estimator/include/bwe_defines.h"
     25 #include "rtc_base/experiments/field_trial_parser.h"
     26 
     27 namespace webrtc {
     28 // A rate control implementation based on additive increases of
     29 // bitrate when no over-use is detected and multiplicative decreases when
     30 // over-uses are detected. When we think the available bandwidth has changes or
     31 // is unknown, we will switch to a "slow-start mode" where we increase
     32 // multiplicatively.
     33 class AimdRateControl {
     34 public:
     35  explicit AimdRateControl(const FieldTrialsView& key_value_config);
     36  AimdRateControl(const FieldTrialsView& key_value_config, bool send_side);
     37  ~AimdRateControl();
     38 
     39  // Returns true if the target bitrate has been initialized. This happens
     40  // either if it has been explicitly set via SetStartBitrate/SetEstimate, or if
     41  // we have measured a throughput.
     42  bool ValidEstimate() const;
     43  void SetStartBitrate(DataRate start_bitrate);
     44  void SetMinBitrate(DataRate min_bitrate);
     45  TimeDelta GetFeedbackInterval() const;
     46 
     47  // Returns true if the bitrate estimate hasn't been changed for more than
     48  // an RTT, or if the estimated_throughput is less than half of the current
     49  // estimate. Should be used to decide if we should reduce the rate further
     50  // when over-using.
     51  bool TimeToReduceFurther(Timestamp at_time,
     52                           DataRate estimated_throughput) const;
     53  // As above. To be used if overusing before we have measured a throughput.
     54  bool InitialTimeToReduceFurther(Timestamp at_time) const;
     55 
     56  DataRate LatestEstimate() const;
     57  void SetRtt(TimeDelta rtt);
     58  DataRate Update(const RateControlInput& input, Timestamp at_time);
     59  void SetInApplicationLimitedRegion(bool in_alr);
     60  void SetEstimate(DataRate bitrate, Timestamp at_time);
     61  void SetNetworkStateEstimate(
     62      const std::optional<NetworkStateEstimate>& estimate);
     63 
     64  // Returns the increase rate when used bandwidth is near the link capacity.
     65  double GetNearMaxIncreaseRateBpsPerSecond() const;
     66  // Returns the expected time between overuse signals (assuming steady state).
     67  TimeDelta GetExpectedBandwidthPeriod() const;
     68 
     69 private:
     70  enum class RateControlState { kRcHold, kRcIncrease, kRcDecrease };
     71 
     72  friend class GoogCcStatePrinter;
     73  // Update the target bitrate based on, among other things, the current rate
     74  // control state, the current target bitrate and the estimated throughput.
     75  // When in the "increase" state the bitrate will be increased either
     76  // additively or multiplicatively depending on the rate control region. When
     77  // in the "decrease" state the bitrate will be decreased to slightly below the
     78  // current throughput. When in the "hold" state the bitrate will be kept
     79  // constant to allow built up queues to drain.
     80  void ChangeBitrate(const RateControlInput& input, Timestamp at_time);
     81 
     82  DataRate ClampBitrate(DataRate new_bitrate) const;
     83  DataRate MultiplicativeRateIncrease(Timestamp at_time,
     84                                      Timestamp last_ms,
     85                                      DataRate current_bitrate) const;
     86  DataRate AdditiveRateIncrease(Timestamp at_time, Timestamp last_time) const;
     87  void UpdateChangePeriod(Timestamp at_time);
     88  void ChangeState(const RateControlInput& input, Timestamp at_time);
     89 
     90  DataRate min_configured_bitrate_;
     91  DataRate max_configured_bitrate_;
     92  DataRate current_bitrate_;
     93  DataRate latest_estimated_throughput_;
     94  LinkCapacityEstimator link_capacity_;
     95  std::optional<NetworkStateEstimate> network_estimate_;
     96  RateControlState rate_control_state_;
     97  Timestamp time_last_bitrate_change_;
     98  Timestamp time_last_bitrate_decrease_;
     99  Timestamp time_first_throughput_estimate_;
    100  bool bitrate_is_initialized_;
    101  double beta_;
    102  bool in_alr_;
    103  TimeDelta rtt_;
    104  const bool send_side_;
    105  // Allow the delay based estimate to only increase as long as application
    106  // limited region (alr) is not detected.
    107  const bool no_bitrate_increase_in_alr_;
    108  // If "Disabled",  estimated link capacity is not used as upper bound.
    109  FieldTrialFlag disable_estimate_bounded_increase_{"Disabled"};
    110  FieldTrialParameter<bool> use_current_estimate_as_min_upper_bound_{"c_upper",
    111                                                                     true};
    112  std::optional<DataRate> last_decrease_;
    113 };
    114 }  // namespace webrtc
    115 
    116 #endif  // MODULES_REMOTE_BITRATE_ESTIMATOR_AIMD_RATE_CONTROL_H_