net/quic/congestion_control/pacing_sender.h

   1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4 //
   5 // A send algorithm that adds pacing on top of an another send algorithm.
   6 // It uses the underlying sender's pacing rate to schedule packets.
   7 // It also takes into consideration the expected granularity of the underlying
   8 // alarm to ensure that alarms are not set too aggressively, and err towards
   9 // sending packets too early instead of too late.
  10
  11 #ifndef NET_QUIC_CONGESTION_CONTROL_PACING_SENDER_H_
  12 #define NET_QUIC_CONGESTION_CONTROL_PACING_SENDER_H_
  13
  14 #include <map>
  15
  16 #include "base/basictypes.h"
  17 #include "base/memory/scoped_ptr.h"
  18 #include "net/quic/congestion_control/send_algorithm_interface.h"
  19 #include "net/quic/quic_bandwidth.h"
  20 #include "net/quic/quic_config.h"
  21 #include "net/quic/quic_protocol.h"
  22 #include "net/quic/quic_time.h"
  23
  24 namespace net {
  25
  26 class NET_EXPORT_PRIVATE PacingSender : public SendAlgorithmInterface {
  27  public:
  28   // Create a PacingSender to wrap the specified sender.  |alarm_granularity|
  29   // indicates to the pacer to send that far into the future, since it should
  30   // not expect a callback before that time delta.  |initial_packet_burst| is
  31   // the number of packets sent without pacing after quiescence.
  32   PacingSender(SendAlgorithmInterface* sender,
  33                QuicTime::Delta alarm_granularity,
  34                uint32 initial_packet_burst);
  35   ~PacingSender() override;
  36
  37   // SendAlgorithmInterface methods.
  38   void SetFromConfig(const QuicConfig& config,
  39                      Perspective perspective) override;
  40   bool ResumeConnectionState(
  41       const CachedNetworkParameters& cached_network_params,
  42       bool max_bandwidth_resumption) override;
  43   void SetNumEmulatedConnections(int num_connections) override;
  44   void SetMaxCongestionWindow(QuicByteCount max_congestion_window) override;
  45   void OnCongestionEvent(bool rtt_updated,
  46                          QuicByteCount bytes_in_flight,
  47                          const CongestionVector& acked_packets,
  48                          const CongestionVector& lost_packets) override;
  49   bool OnPacketSent(QuicTime sent_time,
  50                     QuicByteCount bytes_in_flight,
  51                     QuicPacketSequenceNumber sequence_number,
  52                     QuicByteCount bytes,
  53                     HasRetransmittableData is_retransmittable) override;
  54   void OnRetransmissionTimeout(bool packets_retransmitted) override;
  55   QuicTime::Delta TimeUntilSend(
  56       QuicTime now,
  57       QuicByteCount bytes_in_flight,
  58       HasRetransmittableData has_retransmittable_data) const override;
  59   QuicBandwidth PacingRate() const override;
  60   QuicBandwidth BandwidthEstimate() const override;
  61   bool HasReliableBandwidthEstimate() const override;
  62   QuicTime::Delta RetransmissionDelay() const override;
  63   QuicByteCount GetCongestionWindow() const override;
  64   bool InSlowStart() const override;
  65   bool InRecovery() const override;
  66   QuicByteCount GetSlowStartThreshold() const override;
  67   CongestionControlType GetCongestionControlType() const override;
  68   // End implementation of SendAlgorithmInterface.
  69
  70  private:
  71   scoped_ptr<SendAlgorithmInterface> sender_;  // Underlying sender.
  72   // The estimated system alarm granularity.
  73   const QuicTime::Delta alarm_granularity_;
  74   // Configured size of the burst coming out of quiescence.
  75   const uint32 initial_packet_burst_;
  76   // Number of unpaced packets to be sent before packets are delayed.
  77   uint32 burst_tokens_;
  78   // Send time of the last packet considered delayed.
  79   QuicTime last_delayed_packet_sent_time_;
  80   QuicTime ideal_next_packet_send_time_;  // When can the next packet be sent.
  81   mutable bool was_last_send_delayed_;  // True when the last send was delayed.
  82
  83   DISALLOW_COPY_AND_ASSIGN(PacingSender);
  84 };
  85
  86 }  // namespace net
  87
  88 #endif  // NET_QUIC_CONGESTION_CONTROL_PACING_SENDER_H_