Landing Recent QUIC changes until 9/2/2015 17:00 UTC.

net/quic/congestion_control/cubic.cc

 // Copyright (c) 2012 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/cubic.h"
 
 #include <stdint.h>
 #include <algorithm>
 #include <cmath>
 
@@ skipping 61 matching lines @@
   last_update_time_ = QuicTime::Zero();  // Reset time.
   last_congestion_window_ = 0;
   last_max_congestion_window_ = 0;
   acked_packets_count_ = 0;
   estimated_tcp_congestion_window_ = 0;
   origin_point_congestion_window_ = 0;
   time_to_origin_point_ = 0;
   last_target_congestion_window_ = 0;
 }
 
+void Cubic::OnApplicationLimited() {
+  // When sender is not using the available congestion window, the window does
+  // not grow. But to be RTT-independent, Cubic assumes that the sender has been
+  // using the entire window during the time since the beginning of the current
+  // "epoch" (the end of the last loss recovery period). Since
+  // application-limited periods break this assumption, we reset the epoch when
+  // in such a period. This reset effectively freezes congestion window growth
+  // through application-limited periods and allows Cubic growth to continue
+  // when the entire window is being used.
+  epoch_ = QuicTime::Zero();
+}
+
 QuicPacketCount Cubic::CongestionWindowAfterPacketLoss(
     QuicPacketCount current_congestion_window) {
   if (current_congestion_window < last_max_congestion_window_) {
     // We never reached the old max, so assume we are competing with another
     // flow. Use our extra back off factor to allow the other flow to go up.
     last_max_congestion_window_ =
         static_cast<int>(kBetaLastMax * current_congestion_window);
   } else {
     last_max_congestion_window_ = current_congestion_window;
   }
@@ skipping 64 matching lines @@
 
   // We have a new cubic congestion window.
   last_target_congestion_window_ = target_congestion_window;
 
   // Compute target congestion_window based on cubic target and estimated TCP
   // congestion_window, use highest (fastest).
   if (target_congestion_window < estimated_tcp_congestion_window_) {
     target_congestion_window = estimated_tcp_congestion_window_;
   }
 
-  DVLOG(1) << "Target congestion_window: " << target_congestion_window;
+  DVLOG(1) << "Final target congestion_window: " << target_congestion_window;
   return target_congestion_window;
 }
 
 }  // namespace net