net/quic/congestion_control/tcp_cubic_bytes_sender_test.cc

   1 // Copyright (c) 2015 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/tcp_cubic_bytes_sender.h"
   6
   7 #include <algorithm>
   8
   9 #include "base/logging.h"
  10 #include "base/memory/scoped_ptr.h"
  11 #include "net/quic/congestion_control/rtt_stats.h"
  12 #include "net/quic/crypto/crypto_protocol.h"
  13 #include "net/quic/quic_protocol.h"
  14 #include "net/quic/quic_utils.h"
  15 #include "net/quic/test_tools/mock_clock.h"
  16 #include "net/quic/test_tools/quic_config_peer.h"
  17 #include "testing/gtest/include/gtest/gtest.h"
  18
  19 namespace net {
  20 namespace test {
  21
  22 // TODO(ianswett): A number of theses tests were written with the assumption of
  23 // an initial CWND of 10. They have carefully calculated values which should be
  24 // updated to be based on kInitialCongestionWindowInsecure.
  25 const uint32 kInitialCongestionWindowPackets = 10;
  26 const uint32 kDefaultWindowTCP =
  27     kInitialCongestionWindowPackets * kDefaultTCPMSS;
  28 const float kRenoBeta = 0.7f;  // Reno backoff factor.
  29
  30 class TcpCubicBytesSenderPeer : public TcpCubicBytesSender {
  31  public:
  32   TcpCubicBytesSenderPeer(const QuicClock* clock, bool reno)
  33       : TcpCubicBytesSender(clock,
  34                             &rtt_stats_,
  35                             reno,
  36                             kInitialCongestionWindowPackets,
  37                             kMaxTcpCongestionWindow,
  38                             &stats_) {}
  39
  40   const HybridSlowStart& hybrid_slow_start() const {
  41     return hybrid_slow_start_;
  42   }
  43
  44   float GetRenoBeta() const { return RenoBeta(); }
  45
  46   RttStats rtt_stats_;
  47   QuicConnectionStats stats_;
  48 };
  49
  50 class TcpCubicBytesSenderTest : public ::testing::Test {
  51  protected:
  52   TcpCubicBytesSenderTest()
  53       : one_ms_(QuicTime::Delta::FromMilliseconds(1)),
  54         sender_(new TcpCubicBytesSenderPeer(&clock_, true)),
  55         sequence_number_(1),
  56         acked_sequence_number_(0),
  57         bytes_in_flight_(0) {
  58     standard_packet_.bytes_sent = kDefaultTCPMSS;
  59   }
  60
  61   int SendAvailableSendWindow() {
  62     // Send as long as TimeUntilSend returns Zero.
  63     int packets_sent = 0;
  64     bool can_send = sender_->TimeUntilSend(clock_.Now(), bytes_in_flight_,
  65                                            HAS_RETRANSMITTABLE_DATA).IsZero();
  66     while (can_send) {
  67       sender_->OnPacketSent(clock_.Now(), bytes_in_flight_, sequence_number_++,
  68                             kDefaultTCPMSS, HAS_RETRANSMITTABLE_DATA);
  69       ++packets_sent;
  70       bytes_in_flight_ += kDefaultTCPMSS;
  71       can_send = sender_->TimeUntilSend(clock_.Now(), bytes_in_flight_,
  72                                         HAS_RETRANSMITTABLE_DATA).IsZero();
  73     }
  74     return packets_sent;
  75   }
  76
  77   // Normal is that TCP acks every other segment.
  78   void AckNPackets(int n) {
  79     sender_->rtt_stats_.UpdateRtt(QuicTime::Delta::FromMilliseconds(60),
  80                                   QuicTime::Delta::Zero(), clock_.Now());
  81     SendAlgorithmInterface::CongestionVector acked_packets;
  82     SendAlgorithmInterface::CongestionVector lost_packets;
  83     for (int i = 0; i < n; ++i) {
  84       ++acked_sequence_number_;
  85       acked_packets.push_back(
  86           std::make_pair(acked_sequence_number_, standard_packet_));
  87     }
  88     sender_->OnCongestionEvent(true, bytes_in_flight_, acked_packets,
  89                                lost_packets);
  90     bytes_in_flight_ -= n * kDefaultTCPMSS;
  91     clock_.AdvanceTime(one_ms_);
  92   }
  93
  94   void LoseNPackets(int n) {
  95     SendAlgorithmInterface::CongestionVector acked_packets;
  96     SendAlgorithmInterface::CongestionVector lost_packets;
  97     for (int i = 0; i < n; ++i) {
  98       ++acked_sequence_number_;
  99       lost_packets.push_back(
 100           std::make_pair(acked_sequence_number_, standard_packet_));
 101     }
 102     sender_->OnCongestionEvent(false, bytes_in_flight_, acked_packets,
 103                                lost_packets);
 104     bytes_in_flight_ -= n * kDefaultTCPMSS;
 105   }
 106
 107   // Does not increment acked_sequence_number_.
 108   void LosePacket(QuicPacketSequenceNumber sequence_number) {
 109     SendAlgorithmInterface::CongestionVector acked_packets;
 110     SendAlgorithmInterface::CongestionVector lost_packets;
 111     lost_packets.push_back(std::make_pair(sequence_number, standard_packet_));
 112     sender_->OnCongestionEvent(false, bytes_in_flight_, acked_packets,
 113                                lost_packets);
 114     bytes_in_flight_ -= kDefaultTCPMSS;
 115   }
 116
 117   const QuicTime::Delta one_ms_;
 118   MockClock clock_;
 119   scoped_ptr<TcpCubicBytesSenderPeer> sender_;
 120   QuicPacketSequenceNumber sequence_number_;
 121   QuicPacketSequenceNumber acked_sequence_number_;
 122   QuicByteCount bytes_in_flight_;
 123   TransmissionInfo standard_packet_;
 124 };
 125
 126 TEST_F(TcpCubicBytesSenderTest, SimpleSender) {
 127   // At startup make sure we are at the default.
 128   EXPECT_EQ(kDefaultWindowTCP, sender_->GetCongestionWindow());
 129   // At startup make sure we can send.
 130   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(), 0,
 131                                      HAS_RETRANSMITTABLE_DATA).IsZero());
 132   // Make sure we can send.
 133   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(), 0,
 134                                      HAS_RETRANSMITTABLE_DATA).IsZero());
 135   // And that window is un-affected.
 136   EXPECT_EQ(kDefaultWindowTCP, sender_->GetCongestionWindow());
 137
 138   // Fill the send window with data, then verify that we can't send.
 139   SendAvailableSendWindow();
 140   EXPECT_FALSE(sender_->TimeUntilSend(clock_.Now(),
 141                                       sender_->GetCongestionWindow(),
 142                                       HAS_RETRANSMITTABLE_DATA).IsZero());
 143 }
 144
 145 TEST_F(TcpCubicBytesSenderTest, ApplicationLimitedSlowStart) {
 146   // Send exactly 10 packets and ensure the CWND ends at 14 packets.
 147   const int kNumberOfAcks = 5;
 148   // At startup make sure we can send.
 149   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(), 0,
 150                                      HAS_RETRANSMITTABLE_DATA).IsZero());
 151   // Make sure we can send.
 152   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(), 0,
 153                                      HAS_RETRANSMITTABLE_DATA).IsZero());
 154
 155   SendAvailableSendWindow();
 156   for (int i = 0; i < kNumberOfAcks; ++i) {
 157     AckNPackets(2);
 158   }
 159   QuicByteCount bytes_to_send = sender_->GetCongestionWindow();
 160   // It's expected 2 acks will arrive when the bytes_in_flight are greater than
 161   // half the CWND.
 162   EXPECT_EQ(kDefaultWindowTCP + kDefaultTCPMSS * 2 * 2, bytes_to_send);
 163 }
 164
 165 TEST_F(TcpCubicBytesSenderTest, ExponentialSlowStart) {
 166   const int kNumberOfAcks = 20;
 167   // At startup make sure we can send.
 168   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(), 0,
 169                                      HAS_RETRANSMITTABLE_DATA).IsZero());
 170   EXPECT_FALSE(sender_->HasReliableBandwidthEstimate());
 171   EXPECT_EQ(QuicBandwidth::Zero(), sender_->BandwidthEstimate());
 172   // Make sure we can send.
 173   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(), 0,
 174                                      HAS_RETRANSMITTABLE_DATA).IsZero());
 175
 176   for (int i = 0; i < kNumberOfAcks; ++i) {
 177     // Send our full send window.
 178     SendAvailableSendWindow();
 179     AckNPackets(2);
 180   }
 181   const QuicByteCount cwnd = sender_->GetCongestionWindow();
 182   EXPECT_EQ(kDefaultWindowTCP + kDefaultTCPMSS * 2 * kNumberOfAcks, cwnd);
 183   EXPECT_FALSE(sender_->HasReliableBandwidthEstimate());
 184   EXPECT_EQ(QuicBandwidth::FromBytesAndTimeDelta(
 185                 cwnd, sender_->rtt_stats_.smoothed_rtt()),
 186             sender_->BandwidthEstimate());
 187 }
 188
 189 TEST_F(TcpCubicBytesSenderTest, SlowStartPacketLoss) {
 190   sender_->SetNumEmulatedConnections(1);
 191   const int kNumberOfAcks = 10;
 192   for (int i = 0; i < kNumberOfAcks; ++i) {
 193     // Send our full send window.
 194     SendAvailableSendWindow();
 195     AckNPackets(2);
 196   }
 197   SendAvailableSendWindow();
 198   QuicByteCount expected_send_window =
 199       kDefaultWindowTCP + (kDefaultTCPMSS * 2 * kNumberOfAcks);
 200   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 201
 202   // Lose a packet to exit slow start.
 203   LoseNPackets(1);
 204   size_t packets_in_recovery_window = expected_send_window / kDefaultTCPMSS;
 205
 206   // We should now have fallen out of slow start with a reduced window.
 207   expected_send_window *= kRenoBeta;
 208   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 209
 210   // Recovery phase. We need to ack every packet in the recovery window before
 211   // we exit recovery.
 212   size_t number_of_packets_in_window = expected_send_window / kDefaultTCPMSS;
 213   DVLOG(1) << "number_packets: " << number_of_packets_in_window;
 214   AckNPackets(packets_in_recovery_window);
 215   SendAvailableSendWindow();
 216   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 217
 218   // We need to ack an entire window before we increase CWND by 1.
 219   AckNPackets(number_of_packets_in_window - 2);
 220   SendAvailableSendWindow();
 221   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 222
 223   // Next ack should increase cwnd by 1.
 224   AckNPackets(1);
 225   expected_send_window += kDefaultTCPMSS;
 226   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 227
 228   // Now RTO and ensure slow start gets reset.
 229   EXPECT_TRUE(sender_->hybrid_slow_start().started());
 230   sender_->OnRetransmissionTimeout(true);
 231   EXPECT_FALSE(sender_->hybrid_slow_start().started());
 232 }
 233
 234 TEST_F(TcpCubicBytesSenderTest, NoPRRWhenLessThanOnePacketInFlight) {
 235   SendAvailableSendWindow();
 236   LoseNPackets(kInitialCongestionWindowPackets - 1);
 237   AckNPackets(1);
 238   // PRR will allow 2 packets for every ack during recovery.
 239   EXPECT_EQ(2, SendAvailableSendWindow());
 240   // Simulate abandoning all packets by supplying a bytes_in_flight of 0.
 241   // PRR should now allow a packet to be sent, even though prr's state variables
 242   // believe it has sent enough packets.
 243   EXPECT_EQ(QuicTime::Delta::Zero(),
 244             sender_->TimeUntilSend(clock_.Now(), 0, HAS_RETRANSMITTABLE_DATA));
 245 }
 246
 247 TEST_F(TcpCubicBytesSenderTest, SlowStartPacketLossPRR) {
 248   sender_->SetNumEmulatedConnections(1);
 249   // Test based on the first example in RFC6937.
 250   // Ack 10 packets in 5 acks to raise the CWND to 20, as in the example.
 251   const int kNumberOfAcks = 5;
 252   for (int i = 0; i < kNumberOfAcks; ++i) {
 253     // Send our full send window.
 254     SendAvailableSendWindow();
 255     AckNPackets(2);
 256   }
 257   SendAvailableSendWindow();
 258   QuicByteCount expected_send_window =
 259       kDefaultWindowTCP + (kDefaultTCPMSS * 2 * kNumberOfAcks);
 260   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 261
 262   LoseNPackets(1);
 263
 264   // We should now have fallen out of slow start with a reduced window.
 265   size_t send_window_before_loss = expected_send_window;
 266   expected_send_window *= kRenoBeta;
 267   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 268
 269   // Testing TCP proportional rate reduction.
 270   // We should send packets paced over the received acks for the remaining
 271   // outstanding packets. The number of packets before we exit recovery is the
 272   // original CWND minus the packet that has been lost and the one which
 273   // triggered the loss.
 274   size_t remaining_packets_in_recovery =
 275       send_window_before_loss / kDefaultTCPMSS - 2;
 276
 277   for (size_t i = 0; i < remaining_packets_in_recovery; ++i) {
 278     AckNPackets(1);
 279     SendAvailableSendWindow();
 280     EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 281   }
 282
 283   // We need to ack another window before we increase CWND by 1.
 284   size_t number_of_packets_in_window = expected_send_window / kDefaultTCPMSS;
 285   for (size_t i = 0; i < number_of_packets_in_window; ++i) {
 286     AckNPackets(1);
 287     EXPECT_EQ(1, SendAvailableSendWindow());
 288     EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 289   }
 290
 291   AckNPackets(1);
 292   expected_send_window += kDefaultTCPMSS;
 293   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 294 }
 295
 296 TEST_F(TcpCubicBytesSenderTest, SlowStartBurstPacketLossPRR) {
 297   sender_->SetNumEmulatedConnections(1);
 298   // Test based on the second example in RFC6937, though we also implement
 299   // forward acknowledgements, so the first two incoming acks will trigger
 300   // PRR immediately.
 301   // Ack 20 packets in 10 acks to raise the CWND to 30.
 302   const int kNumberOfAcks = 10;
 303   for (int i = 0; i < kNumberOfAcks; ++i) {
 304     // Send our full send window.
 305     SendAvailableSendWindow();
 306     AckNPackets(2);
 307   }
 308   SendAvailableSendWindow();
 309   QuicByteCount expected_send_window =
 310       kDefaultWindowTCP + (kDefaultTCPMSS * 2 * kNumberOfAcks);
 311   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 312
 313   // Lose one more than the congestion window reduction, so that after loss,
 314   // bytes_in_flight is lesser than the congestion window.
 315   size_t send_window_after_loss = kRenoBeta * expected_send_window;
 316   size_t num_packets_to_lose =
 317       (expected_send_window - send_window_after_loss) / kDefaultTCPMSS + 1;
 318   LoseNPackets(num_packets_to_lose);
 319   // Immediately after the loss, ensure at least one packet can be sent.
 320   // Losses without subsequent acks can occur with timer based loss detection.
 321   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(), bytes_in_flight_,
 322                                      HAS_RETRANSMITTABLE_DATA).IsZero());
 323   AckNPackets(1);
 324
 325   // We should now have fallen out of slow start with a reduced window.
 326   expected_send_window *= kRenoBeta;
 327   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 328
 329   // Only 2 packets should be allowed to be sent, per PRR-SSRB.
 330   EXPECT_EQ(2, SendAvailableSendWindow());
 331
 332   // Ack the next packet, which triggers another loss.
 333   LoseNPackets(1);
 334   AckNPackets(1);
 335
 336   // Send 2 packets to simulate PRR-SSRB.
 337   EXPECT_EQ(2, SendAvailableSendWindow());
 338
 339   // Ack the next packet, which triggers another loss.
 340   LoseNPackets(1);
 341   AckNPackets(1);
 342
 343   // Send 2 packets to simulate PRR-SSRB.
 344   EXPECT_EQ(2, SendAvailableSendWindow());
 345
 346   // Exit recovery and return to sending at the new rate.
 347   for (int i = 0; i < kNumberOfAcks; ++i) {
 348     AckNPackets(1);
 349     EXPECT_EQ(1, SendAvailableSendWindow());
 350   }
 351 }
 352
 353 TEST_F(TcpCubicBytesSenderTest, RTOCongestionWindow) {
 354   EXPECT_EQ(kDefaultWindowTCP, sender_->GetCongestionWindow());
 355   // Expect the window to decrease to the minimum once the RTO fires and slow
 356   // start threshold to be set to 1/2 of the CWND.
 357   sender_->OnRetransmissionTimeout(true);
 358   EXPECT_EQ(2 * kDefaultTCPMSS, sender_->GetCongestionWindow());
 359   EXPECT_EQ(5u * kDefaultTCPMSS, sender_->GetSlowStartThreshold());
 360 }
 361
 362 TEST_F(TcpCubicBytesSenderTest, RTOCongestionWindowNoRetransmission) {
 363   EXPECT_EQ(kDefaultWindowTCP, sender_->GetCongestionWindow());
 364
 365   // Expect the window to remain unchanged if the RTO fires but no packets are
 366   // retransmitted.
 367   sender_->OnRetransmissionTimeout(false);
 368   EXPECT_EQ(kDefaultWindowTCP, sender_->GetCongestionWindow());
 369 }
 370
 371 TEST_F(TcpCubicBytesSenderTest, RetransmissionDelay) {
 372   const int64 kRttMs = 10;
 373   const int64 kDeviationMs = 3;
 374   EXPECT_EQ(QuicTime::Delta::Zero(), sender_->RetransmissionDelay());
 375
 376   sender_->rtt_stats_.UpdateRtt(QuicTime::Delta::FromMilliseconds(kRttMs),
 377                                 QuicTime::Delta::Zero(), clock_.Now());
 378
 379   // Initial value is to set the median deviation to half of the initial rtt,
 380   // the median in then multiplied by a factor of 4 and finally the smoothed rtt
 381   // is added which is the initial rtt.
 382   QuicTime::Delta expected_delay =
 383       QuicTime::Delta::FromMilliseconds(kRttMs + kRttMs / 2 * 4);
 384   EXPECT_EQ(expected_delay, sender_->RetransmissionDelay());
 385
 386   for (int i = 0; i < 100; ++i) {
 387     // Run to make sure that we converge.
 388     sender_->rtt_stats_.UpdateRtt(
 389         QuicTime::Delta::FromMilliseconds(kRttMs + kDeviationMs),
 390         QuicTime::Delta::Zero(), clock_.Now());
 391     sender_->rtt_stats_.UpdateRtt(
 392         QuicTime::Delta::FromMilliseconds(kRttMs - kDeviationMs),
 393         QuicTime::Delta::Zero(), clock_.Now());
 394   }
 395   expected_delay = QuicTime::Delta::FromMilliseconds(kRttMs + kDeviationMs * 4);
 396
 397   EXPECT_NEAR(kRttMs, sender_->rtt_stats_.smoothed_rtt().ToMilliseconds(), 1);
 398   EXPECT_NEAR(expected_delay.ToMilliseconds(),
 399               sender_->RetransmissionDelay().ToMilliseconds(), 1);
 400   EXPECT_EQ(
 401       static_cast<int64>(sender_->GetCongestionWindow() * kNumMicrosPerSecond /
 402                          sender_->rtt_stats_.smoothed_rtt().ToMicroseconds()),
 403       sender_->BandwidthEstimate().ToBytesPerSecond());
 404 }
 405
 406 TEST_F(TcpCubicBytesSenderTest, MultipleLossesInOneWindow) {
 407   SendAvailableSendWindow();
 408   const QuicByteCount initial_window = sender_->GetCongestionWindow();
 409   LosePacket(acked_sequence_number_ + 1);
 410   const QuicByteCount post_loss_window = sender_->GetCongestionWindow();
 411   EXPECT_GT(initial_window, post_loss_window);
 412   LosePacket(acked_sequence_number_ + 3);
 413   EXPECT_EQ(post_loss_window, sender_->GetCongestionWindow());
 414   LosePacket(sequence_number_ - 1);
 415   EXPECT_EQ(post_loss_window, sender_->GetCongestionWindow());
 416
 417   // Lose a later packet and ensure the window decreases.
 418   LosePacket(sequence_number_);
 419   EXPECT_GT(post_loss_window, sender_->GetCongestionWindow());
 420 }
 421
 422 TEST_F(TcpCubicBytesSenderTest, DontTrackAckPackets) {
 423   // Send a packet with no retransmittable data, and ensure it's not tracked.
 424   EXPECT_FALSE(sender_->OnPacketSent(clock_.Now(), bytes_in_flight_,
 425                                      sequence_number_++, kDefaultTCPMSS,
 426                                      NO_RETRANSMITTABLE_DATA));
 427
 428   // Send a data packet with retransmittable data, and ensure it is tracked.
 429   EXPECT_TRUE(sender_->OnPacketSent(clock_.Now(), bytes_in_flight_,
 430                                     sequence_number_++, kDefaultTCPMSS,
 431                                     HAS_RETRANSMITTABLE_DATA));
 432 }
 433
 434 TEST_F(TcpCubicBytesSenderTest, ConfigureMaxInitialWindow) {
 435   QuicConfig config;
 436
 437   // Verify that kCOPT: kIW10 forces the congestion window to the default of 10.
 438   QuicTagVector options;
 439   options.push_back(kIW10);
 440   QuicConfigPeer::SetReceivedConnectionOptions(&config, options);
 441   sender_->SetFromConfig(config, Perspective::IS_SERVER);
 442   EXPECT_EQ(10u * kDefaultTCPMSS, sender_->GetCongestionWindow());
 443 }
 444
 445 TEST_F(TcpCubicBytesSenderTest, 2ConnectionCongestionAvoidanceAtEndOfRecovery) {
 446   sender_->SetNumEmulatedConnections(2);
 447   // Ack 10 packets in 5 acks to raise the CWND to 20.
 448   const int kNumberOfAcks = 5;
 449   for (int i = 0; i < kNumberOfAcks; ++i) {
 450     // Send our full send window.
 451     SendAvailableSendWindow();
 452     AckNPackets(2);
 453   }
 454   SendAvailableSendWindow();
 455   QuicByteCount expected_send_window =
 456       kDefaultWindowTCP + (kDefaultTCPMSS * 2 * kNumberOfAcks);
 457   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 458
 459   LoseNPackets(1);
 460
 461   // We should now have fallen out of slow start with a reduced window.
 462   expected_send_window = expected_send_window * sender_->GetRenoBeta();
 463   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 464
 465   // No congestion window growth should occur in recovery phase, i.e., until the
 466   // currently outstanding 20 packets are acked.
 467   for (int i = 0; i < 10; ++i) {
 468     // Send our full send window.
 469     SendAvailableSendWindow();
 470     EXPECT_TRUE(sender_->InRecovery());
 471     AckNPackets(2);
 472     EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 473   }
 474   EXPECT_FALSE(sender_->InRecovery());
 475
 476   // Out of recovery now. Congestion window should not grow for half an RTT.
 477   size_t packets_in_send_window = expected_send_window / kDefaultTCPMSS;
 478   SendAvailableSendWindow();
 479   AckNPackets(packets_in_send_window / 2 - 2);
 480   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 481
 482   // Next ack should increase congestion window by 1MSS.
 483   SendAvailableSendWindow();
 484   AckNPackets(2);
 485   expected_send_window += kDefaultTCPMSS;
 486   packets_in_send_window += 1;
 487   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 488
 489   // Congestion window should remain steady again for half an RTT.
 490   SendAvailableSendWindow();
 491   AckNPackets(packets_in_send_window / 2 - 1);
 492   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 493
 494   // Next ack should cause congestion window to grow by 1MSS.
 495   SendAvailableSendWindow();
 496   AckNPackets(2);
 497   expected_send_window += kDefaultTCPMSS;
 498   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 499 }
 500
 501 TEST_F(TcpCubicBytesSenderTest, 1ConnectionCongestionAvoidanceAtEndOfRecovery) {
 502   sender_->SetNumEmulatedConnections(1);
 503   // Ack 10 packets in 5 acks to raise the CWND to 20.
 504   const int kNumberOfAcks = 5;
 505   for (int i = 0; i < kNumberOfAcks; ++i) {
 506     // Send our full send window.
 507     SendAvailableSendWindow();
 508     AckNPackets(2);
 509   }
 510   SendAvailableSendWindow();
 511   QuicByteCount expected_send_window =
 512       kDefaultWindowTCP + (kDefaultTCPMSS * 2 * kNumberOfAcks);
 513   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 514
 515   LoseNPackets(1);
 516
 517   // We should now have fallen out of slow start with a reduced window.
 518   expected_send_window *= kRenoBeta;
 519   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 520
 521   // No congestion window growth should occur in recovery phase, i.e., until the
 522   // currently outstanding 20 packets are acked.
 523   for (int i = 0; i < 10; ++i) {
 524     // Send our full send window.
 525     SendAvailableSendWindow();
 526     EXPECT_TRUE(sender_->InRecovery());
 527     AckNPackets(2);
 528     EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 529   }
 530   EXPECT_FALSE(sender_->InRecovery());
 531
 532   // Out of recovery now. Congestion window should not grow during RTT.
 533   for (uint64 i = 0; i < expected_send_window / kDefaultTCPMSS - 2; i += 2) {
 534     // Send our full send window.
 535     SendAvailableSendWindow();
 536     AckNPackets(2);
 537     EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 538   }
 539
 540   // Next ack should cause congestion window to grow by 1MSS.
 541   SendAvailableSendWindow();
 542   AckNPackets(2);
 543   expected_send_window += kDefaultTCPMSS;
 544   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 545 }
 546
 547 TEST_F(TcpCubicBytesSenderTest, BandwidthResumption) {
 548   // Test that when provided with CachedNetworkParameters and opted in to the
 549   // bandwidth resumption experiment, that the TcpCubicSender sets initial CWND
 550   // appropriately.
 551
 552   // Set some common values.
 553   CachedNetworkParameters cached_network_params;
 554   const QuicPacketCount kNumberOfPackets = 123;
 555   const int kBandwidthEstimateBytesPerSecond =
 556       kNumberOfPackets * kDefaultTCPMSS;
 557   cached_network_params.set_bandwidth_estimate_bytes_per_second(
 558       kBandwidthEstimateBytesPerSecond);
 559   cached_network_params.set_min_rtt_ms(1000);
 560
 561   // Ensure that an old estimate is not used for bandwidth resumption.
 562   cached_network_params.set_timestamp(clock_.WallNow().ToUNIXSeconds() -
 563                                       (kNumSecondsPerHour + 1));
 564   EXPECT_FALSE(sender_->ResumeConnectionState(cached_network_params, false));
 565   EXPECT_EQ(10u * kDefaultTCPMSS, sender_->GetCongestionWindow());
 566
 567   // If the estimate is new enough, make sure it is used.
 568   cached_network_params.set_timestamp(clock_.WallNow().ToUNIXSeconds() -
 569                                       (kNumSecondsPerHour - 1));
 570   EXPECT_TRUE(sender_->ResumeConnectionState(cached_network_params, false));
 571   EXPECT_EQ(kNumberOfPackets * kDefaultTCPMSS, sender_->GetCongestionWindow());
 572
 573   // Resumed CWND is limited to be in a sensible range.
 574   cached_network_params.set_bandwidth_estimate_bytes_per_second(
 575       (kMaxTcpCongestionWindow + 1) * kDefaultTCPMSS);
 576   EXPECT_TRUE(sender_->ResumeConnectionState(cached_network_params, false));
 577   EXPECT_EQ(kMaxTcpCongestionWindow * kDefaultTCPMSS,
 578             sender_->GetCongestionWindow());
 579
 580   cached_network_params.set_bandwidth_estimate_bytes_per_second(
 581       (kMinCongestionWindowForBandwidthResumption - 1) * kDefaultTCPMSS);
 582   EXPECT_TRUE(sender_->ResumeConnectionState(cached_network_params, false));
 583   EXPECT_EQ(kMinCongestionWindowForBandwidthResumption * kDefaultTCPMSS,
 584             sender_->GetCongestionWindow());
 585
 586   // Resume to the max value.
 587   cached_network_params.set_max_bandwidth_estimate_bytes_per_second(
 588       (kMinCongestionWindowForBandwidthResumption + 10) * kDefaultTCPMSS);
 589   EXPECT_TRUE(sender_->ResumeConnectionState(cached_network_params, true));
 590   EXPECT_EQ((kMinCongestionWindowForBandwidthResumption + 10) * kDefaultTCPMSS,
 591             sender_->GetCongestionWindow());
 592 }
 593
 594 }  // namespace test
 595 }  // namespace net