Allow QUIC's BBR TCP sender to pace based on min rtt and add an explicit

net/quic/congestion_control/pacing_sender.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/quic/congestion_control/pacing_sender.h"
 
 namespace net {
 
 PacingSender::PacingSender(SendAlgorithmInterface* sender,
                            QuicTime::Delta alarm_granularity,
@@ skipping 44 matching lines @@
   if (has_retransmittable_data != HAS_RETRANSMITTABLE_DATA) {
     return in_flight;
   }
   if (burst_tokens_ > 0) {
     --burst_tokens_;
     was_last_send_delayed_ = false;
     last_delayed_packet_sent_time_ = QuicTime::Zero();
     next_packet_send_time_ = QuicTime::Zero();
     return in_flight;
   }
-  // The next packet should be sent as soon as the current packets has
-  // been transferred.  We pace at twice the rate of the underlying
-  // sender's bandwidth estimate during slow start and 1.25x during congestion
-  // avoidance to ensure pacing doesn't prevent us from filling the window.
-  const float kPacingAggression = sender_->InSlowStart() ? 2 : 1.25;
-  QuicTime::Delta delay =
-      BandwidthEstimate().Scale(kPacingAggression).TransferTime(bytes);
+  // The next packet should be sent as soon as the current packets has been
+  // transferred.
+  QuicTime::Delta delay = PacingRate().TransferTime(bytes);
   // If the last send was delayed, and the alarm took a long time to get
   // invoked, allow the connection to make up for lost time.
   if (was_last_send_delayed_) {
     next_packet_send_time_ = next_packet_send_time_.Add(delay);
     // The send was application limited if it takes longer than the
     // pacing delay between sent packets.
     const bool application_limited =
         last_delayed_packet_sent_time_.IsInitialized() &&
         sent_time > last_delayed_packet_sent_time_.Add(delay);
     const bool making_up_for_lost_time = next_packet_send_time_ <= sent_time;
@@ skipping 56 matching lines @@
     DVLOG(1) << "Delaying packet: "
              << next_packet_send_time_.Subtract(now).ToMicroseconds();
     was_last_send_delayed_ = true;
     return next_packet_send_time_.Subtract(now);
   }
 
   DVLOG(1) << "Sending packet now";
   return QuicTime::Delta::Zero();
 }
 
+QuicBandwidth PacingSender::PacingRate() const {
+  return sender_->PacingRate();
+}
+
 QuicBandwidth PacingSender::BandwidthEstimate() const {
   return sender_->BandwidthEstimate();
 }
 
 bool PacingSender::HasReliableBandwidthEstimate() const {
   return sender_->HasReliableBandwidthEstimate();
 }
 
 QuicTime::Delta PacingSender::RetransmissionDelay() const {
   return sender_->RetransmissionDelay();
@@ skipping 13 matching lines @@
 
 QuicByteCount PacingSender::GetSlowStartThreshold() const {
   return sender_->GetSlowStartThreshold();
 }
 
 CongestionControlType PacingSender::GetCongestionControlType() const {
   return sender_->GetCongestionControlType();
 }
 
 }  // namespace net