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 which adds pacing on top of an another send algorithm.
6// It uses the underlying sender's bandwidth estimate to determine the
7// pacing rate to be used.  It also takes into consideration the expected
8// resolution of the underlying alarm mechanism to ensure that alarms are
9// not set too aggressively, and to smooth out variations.
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
24namespace net {
25
26class NET_EXPORT_PRIVATE PacingSender : public SendAlgorithmInterface {
27 public:
28  PacingSender(SendAlgorithmInterface* sender,
29               QuicTime::Delta alarm_granularity);
30  virtual ~PacingSender();
31
32  // SendAlgorithmInterface methods.
33  virtual void SetFromConfig(const QuicConfig& config, bool is_server) OVERRIDE;
34  virtual void OnIncomingQuicCongestionFeedbackFrame(
35      const QuicCongestionFeedbackFrame& feedback,
36      QuicTime feedback_receive_time) OVERRIDE;
37  virtual void OnCongestionEvent(bool rtt_updated,
38                                 QuicByteCount bytes_in_flight,
39                                 const CongestionMap& acked_packets,
40                                 const CongestionMap& lost_packets) OVERRIDE;
41  virtual bool OnPacketSent(QuicTime sent_time,
42                            QuicByteCount bytes_in_flight,
43                            QuicPacketSequenceNumber sequence_number,
44                            QuicByteCount bytes,
45                            HasRetransmittableData is_retransmittable) OVERRIDE;
46  virtual void OnRetransmissionTimeout(bool packets_retransmitted) OVERRIDE;
47  virtual QuicTime::Delta TimeUntilSend(
48      QuicTime now,
49      QuicByteCount bytes_in_flight,
50      HasRetransmittableData has_retransmittable_data) const OVERRIDE;
51  virtual QuicBandwidth BandwidthEstimate() const OVERRIDE;
52  virtual QuicTime::Delta RetransmissionDelay() const OVERRIDE;
53  virtual QuicByteCount GetCongestionWindow() const OVERRIDE;
54
55 private:
56  scoped_ptr<SendAlgorithmInterface> sender_;  // Underlying sender.
57  QuicTime::Delta alarm_granularity_;
58  // Send time of the last packet considered delayed.
59  QuicTime last_delayed_packet_sent_time_;
60  QuicTime next_packet_send_time_;  // When can the next packet be sent.
61  mutable bool was_last_send_delayed_;  // True when the last send was delayed.
62  bool has_valid_rtt_;  // True if we have at least one RTT update.
63
64  DISALLOW_COPY_AND_ASSIGN(PacingSender);
65};
66
67}  // namespace net
68
69#endif  // NET_QUIC_CONGESTION_CONTROL_PACING_SENDER_H_
70