src/net/quic/congestion_control/paced_sender.cc

   1 // Copyright (c) 2012 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 #include "net/quic/congestion_control/paced_sender.h"
   6
   7 #include <algorithm>
   8
   9 #include "net/quic/quic_protocol.h"
  10
  11 namespace net {
  12
  13 // To prevent too aggressive pacing we allow the following packet burst size.
  14 const int64 kMinPacketBurstSize = 2;
  15 // Max estimated time between calls to TimeUntilSend and
  16 // AvailableCongestionWindow.
  17 const int64 kMaxSchedulingDelayUs = 2000;
  18
  19 PacedSender::PacedSender(QuicBandwidth estimate, QuicByteCount max_segment_size)
  20     : leaky_bucket_(estimate),
  21       pace_(estimate),
  22       max_segment_size_(kDefaultMaxPacketSize) {
  23 }
  24
  25 void PacedSender::set_max_segment_size(QuicByteCount max_segment_size) {
  26   max_segment_size_ = max_segment_size;
  27 }
  28
  29 void PacedSender::UpdateBandwidthEstimate(QuicTime now,
  30                                           QuicBandwidth estimate) {
  31   leaky_bucket_.SetDrainingRate(now, estimate);
  32   pace_ = estimate;
  33 }
  34
  35 void PacedSender::OnPacketSent(QuicTime now, QuicByteCount bytes) {
  36   leaky_bucket_.Add(now, bytes);
  37 }
  38
  39 QuicTime::Delta PacedSender::TimeUntilSend(QuicTime now,
  40                                            QuicTime::Delta time_until_send) {
  41   if (time_until_send.ToMicroseconds() >= kMaxSchedulingDelayUs) {
  42     return time_until_send;
  43   }
  44   // Pace the data.
  45   QuicByteCount pacing_window = pace_.ToBytesPerPeriod(
  46       QuicTime::Delta::FromMicroseconds(kMaxSchedulingDelayUs));
  47   QuicByteCount min_window_size = kMinPacketBurstSize *  max_segment_size_;
  48   pacing_window = std::max(pacing_window, min_window_size);
  49
  50   if (pacing_window > leaky_bucket_.BytesPending(now)) {
  51     // We have not filled our pacing window yet.
  52     return time_until_send;
  53   }
  54   return leaky_bucket_.TimeRemaining(now);
  55 }
  56
  57 }  // namespace net