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/proto/cached_network_parameters.pb.h"
  14 #include "net/quic/quic_protocol.h"
  15 #include "net/quic/quic_utils.h"
  16 #include "net/quic/test_tools/mock_clock.h"
  17 #include "net/quic/test_tools/quic_config_peer.h"
  18 #include "testing/gtest/include/gtest/gtest.h"
  19
  20 namespace net {
  21 namespace test {
  22
  23 // TODO(ianswett): A number of theses tests were written with the assumption of
  24 // an initial CWND of 10. They have carefully calculated values which should be
  25 // updated to be based on kInitialCongestionWindowInsecure.
  26 const uint32 kInitialCongestionWindowPackets = 10;
  27 const uint32 kDefaultWindowTCP =
  28     kInitialCongestionWindowPackets * kDefaultTCPMSS;
  29 const float kRenoBeta = 0.7f;  // Reno backoff factor.
  30
  31 class TcpCubicBytesSenderPeer : public TcpCubicBytesSender {
  32  public:
  33   TcpCubicBytesSenderPeer(const QuicClock* clock, bool reno)
  34       : TcpCubicBytesSender(clock,
  35                             &rtt_stats_,
  36                             reno,
  37                             kInitialCongestionWindowPackets,
  38                             kMaxCongestionWindow,
  39                             &stats_) {}
  40
  41   const HybridSlowStart& hybrid_slow_start() const {
  42     return hybrid_slow_start_;
  43   }
  44
  45   float GetRenoBeta() const { return RenoBeta(); }
  46
  47   RttStats rtt_stats_;
  48   QuicConnectionStats stats_;
  49 };
  50
  51 class TcpCubicBytesSenderTest : public ::testing::Test {
  52  protected:
  53   TcpCubicBytesSenderTest()
  54       : one_ms_(QuicTime::Delta::FromMilliseconds(1)),
  55         sender_(new TcpCubicBytesSenderPeer(&clock_, true)),
  56         sequence_number_(1),
  57         acked_sequence_number_(0),
  58         bytes_in_flight_(0) {
  59     standard_packet_.bytes_sent = kDefaultTCPMSS;
  60   }
  61
  62   int SendAvailableSendWindow() {
  63     // Send as long as TimeUntilSend returns Zero.
  64     int packets_sent = 0;
  65     bool can_send = sender_->TimeUntilSend(clock_.Now(), bytes_in_flight_,
  66                                            HAS_RETRANSMITTABLE_DATA).IsZero();
  67     while (can_send) {
  68       sender_->OnPacketSent(clock_.Now(), bytes_in_flight_, sequence_number_++,
  69                             kDefaultTCPMSS, HAS_RETRANSMITTABLE_DATA);
  70       ++packets_sent;
  71       bytes_in_flight_ += kDefaultTCPMSS;
  72       can_send = sender_->TimeUntilSend(clock_.Now(), bytes_in_flight_,
  73                                         HAS_RETRANSMITTABLE_DATA).IsZero();
  74     }
  75     return packets_sent;
  76   }
  77
  78   // Normal is that TCP acks every other segment.
  79   void AckNPackets(int n) {
  80     sender_->rtt_stats_.UpdateRtt(QuicTime::Delta::FromMilliseconds(60),
  81                                   QuicTime::Delta::Zero(), clock_.Now());
  82     SendAlgorithmInterface::CongestionVector acked_packets;
  83     SendAlgorithmInterface::CongestionVector lost_packets;
  84     for (int i = 0; i < n; ++i) {
  85       ++acked_sequence_number_;
  86       acked_packets.push_back(
  87           std::make_pair(acked_sequence_number_, standard_packet_));
  88     }
  89     sender_->OnCongestionEvent(true, bytes_in_flight_, acked_packets,
  90                                lost_packets);
  91     bytes_in_flight_ -= n * kDefaultTCPMSS;
  92     clock_.AdvanceTime(one_ms_);
  93   }
  94
  95   void LoseNPackets(int n) {
  96     SendAlgorithmInterface::CongestionVector acked_packets;
  97     SendAlgorithmInterface::CongestionVector lost_packets;
  98     for (int i = 0; i < n; ++i) {
  99       ++acked_sequence_number_;
 100       lost_packets.push_back(
 101           std::make_pair(acked_sequence_number_, standard_packet_));
 102     }
 103     sender_->OnCongestionEvent(false, bytes_in_flight_, acked_packets,
 104                                lost_packets);
 105     bytes_in_flight_ -= n * kDefaultTCPMSS;
 106   }
 107
 108   // Does not increment acked_sequence_number_.
 109   void LosePacket(QuicPacketSequenceNumber sequence_number) {
 110     SendAlgorithmInterface::CongestionVector acked_packets;
 111     SendAlgorithmInterface::CongestionVector lost_packets;
 112     lost_packets.push_back(std::make_pair(sequence_number, standard_packet_));
 113     sender_->OnCongestionEvent(false, bytes_in_flight_, acked_packets,
 114                                lost_packets);
 115     bytes_in_flight_ -= kDefaultTCPMSS;
 116   }
 117
 118   const QuicTime::Delta one_ms_;
 119   MockClock clock_;
 120   scoped_ptr<TcpCubicBytesSenderPeer> sender_;
 121   QuicPacketSequenceNumber sequence_number_;
 122   QuicPacketSequenceNumber acked_sequence_number_;
 123   QuicByteCount bytes_in_flight_;
 124   TransmissionInfo standard_packet_;
 125 };
 126
 127 TEST_F(TcpCubicBytesSenderTest, SimpleSender) {
 128   // At startup make sure we are at the default.
 129   EXPECT_EQ(kDefaultWindowTCP, sender_->GetCongestionWindow());
 130   // At startup make sure we can send.
 131   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(), 0,
 132                                      HAS_RETRANSMITTABLE_DATA).IsZero());
 133   // Make sure we can send.
 134   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(), 0,
 135                                      HAS_RETRANSMITTABLE_DATA).IsZero());
 136   // And that window is un-affected.
 137   EXPECT_EQ(kDefaultWindowTCP, sender_->GetCongestionWindow());
 138
 139   // Fill the send window with data, then verify that we can't send.
 140   SendAvailableSendWindow();
 141   EXPECT_FALSE(sender_->TimeUntilSend(clock_.Now(),
 142                                       sender_->GetCongestionWindow(),
 143                                       HAS_RETRANSMITTABLE_DATA).IsZero());
 144 }
 145
 146 TEST_F(TcpCubicBytesSenderTest, ApplicationLimitedSlowStart) {
 147   // Send exactly 10 packets and ensure the CWND ends at 14 packets.
 148   const int kNumberOfAcks = 5;
 149   // At startup make sure we can send.
 150   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(), 0,
 151                                      HAS_RETRANSMITTABLE_DATA).IsZero());
 152   // Make sure we can send.
 153   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(), 0,
 154                                      HAS_RETRANSMITTABLE_DATA).IsZero());
 155
 156   SendAvailableSendWindow();
 157   for (int i = 0; i < kNumberOfAcks; ++i) {
 158     AckNPackets(2);
 159   }
 160   QuicByteCount bytes_to_send = sender_->GetCongestionWindow();
 161   // It's expected 2 acks will arrive when the bytes_in_flight are greater than
 162   // half the CWND.
 163   EXPECT_EQ(kDefaultWindowTCP + kDefaultTCPMSS * 2 * 2, bytes_to_send);
 164 }
 165
 166 TEST_F(TcpCubicBytesSenderTest, ExponentialSlowStart) {
 167   const int kNumberOfAcks = 20;
 168   // At startup make sure we can send.
 169   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(), 0,
 170                                      HAS_RETRANSMITTABLE_DATA).IsZero());
 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_EQ(QuicBandwidth::FromBytesAndTimeDelta(
 184                 cwnd, sender_->rtt_stats_.smoothed_rtt()),
 185             sender_->BandwidthEstimate());
 186 }
 187
 188 TEST_F(TcpCubicBytesSenderTest, SlowStartPacketLoss) {
 189   sender_->SetNumEmulatedConnections(1);
 190   const int kNumberOfAcks = 10;
 191   for (int i = 0; i < kNumberOfAcks; ++i) {
 192     // Send our full send window.
 193     SendAvailableSendWindow();
 194     AckNPackets(2);
 195   }
 196   SendAvailableSendWindow();
 197   QuicByteCount expected_send_window =
 198       kDefaultWindowTCP + (kDefaultTCPMSS * 2 * kNumberOfAcks);
 199   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 200
 201   // Lose a packet to exit slow start.
 202   LoseNPackets(1);
 203   size_t packets_in_recovery_window = expected_send_window / kDefaultTCPMSS;
 204
 205   // We should now have fallen out of slow start with a reduced window.
 206   expected_send_window *= kRenoBeta;
 207   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 208
 209   // Recovery phase. We need to ack every packet in the recovery window before
 210   // we exit recovery.
 211   size_t number_of_packets_in_window = expected_send_window / kDefaultTCPMSS;
 212   DVLOG(1) << "number_packets: " << number_of_packets_in_window;
 213   AckNPackets(packets_in_recovery_window);
 214   SendAvailableSendWindow();
 215   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 216
 217   // We need to ack an entire window before we increase CWND by 1.
 218   AckNPackets(number_of_packets_in_window - 2);
 219   SendAvailableSendWindow();
 220   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 221
 222   // Next ack should increase cwnd by 1.
 223   AckNPackets(1);
 224   expected_send_window += kDefaultTCPMSS;
 225   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 226
 227   // Now RTO and ensure slow start gets reset.
 228   EXPECT_TRUE(sender_->hybrid_slow_start().started());
 229   sender_->OnRetransmissionTimeout(true);
 230   EXPECT_FALSE(sender_->hybrid_slow_start().started());
 231 }
 232
 233 TEST_F(TcpCubicBytesSenderTest, NoPRRWhenLessThanOnePacketInFlight) {
 234   SendAvailableSendWindow();
 235   LoseNPackets(kInitialCongestionWindowPackets - 1);
 236   AckNPackets(1);
 237   // PRR will allow 2 packets for every ack during recovery.
 238   EXPECT_EQ(2, SendAvailableSendWindow());
 239   // Simulate abandoning all packets by supplying a bytes_in_flight of 0.
 240   // PRR should now allow a packet to be sent, even though prr's state variables
 241   // believe it has sent enough packets.
 242   EXPECT_EQ(QuicTime::Delta::Zero(),
 243             sender_->TimeUntilSend(clock_.Now(), 0, HAS_RETRANSMITTABLE_DATA));
 244 }
 245
 246 TEST_F(TcpCubicBytesSenderTest, SlowStartPacketLossPRR) {
 247   sender_->SetNumEmulatedConnections(1);
 248   // Test based on the first example in RFC6937.
 249   // Ack 10 packets in 5 acks to raise the CWND to 20, as in the example.
 250   const int kNumberOfAcks = 5;
 251   for (int i = 0; i < kNumberOfAcks; ++i) {
 252     // Send our full send window.
 253     SendAvailableSendWindow();
 254     AckNPackets(2);
 255   }
 256   SendAvailableSendWindow();
 257   QuicByteCount expected_send_window =
 258       kDefaultWindowTCP + (kDefaultTCPMSS * 2 * kNumberOfAcks);
 259   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 260
 261   LoseNPackets(1);
 262
 263   // We should now have fallen out of slow start with a reduced window.
 264   size_t send_window_before_loss = expected_send_window;
 265   expected_send_window *= kRenoBeta;
 266   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 267
 268   // Testing TCP proportional rate reduction.
 269   // We should send packets paced over the received acks for the remaining
 270   // outstanding packets. The number of packets before we exit recovery is the
 271   // original CWND minus the packet that has been lost and the one which
 272   // triggered the loss.
 273   size_t remaining_packets_in_recovery =
 274       send_window_before_loss / kDefaultTCPMSS - 2;
 275
 276   for (size_t i = 0; i < remaining_packets_in_recovery; ++i) {
 277     AckNPackets(1);
 278     SendAvailableSendWindow();
 279     EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 280   }
 281
 282   // We need to ack another window before we increase CWND by 1.
 283   size_t number_of_packets_in_window = expected_send_window / kDefaultTCPMSS;
 284   for (size_t i = 0; i < number_of_packets_in_window; ++i) {
 285     AckNPackets(1);
 286     EXPECT_EQ(1, SendAvailableSendWindow());
 287     EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 288   }
 289
 290   AckNPackets(1);
 291   expected_send_window += kDefaultTCPMSS;
 292   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 293 }
 294
 295 TEST_F(TcpCubicBytesSenderTest, SlowStartBurstPacketLossPRR) {
 296   sender_->SetNumEmulatedConnections(1);
 297   // Test based on the second example in RFC6937, though we also implement
 298   // forward acknowledgements, so the first two incoming acks will trigger
 299   // PRR immediately.
 300   // Ack 20 packets in 10 acks to raise the CWND to 30.
 301   const int kNumberOfAcks = 10;
 302   for (int i = 0; i < kNumberOfAcks; ++i) {
 303     // Send our full send window.
 304     SendAvailableSendWindow();
 305     AckNPackets(2);
 306   }
 307   SendAvailableSendWindow();
 308   QuicByteCount expected_send_window =
 309       kDefaultWindowTCP + (kDefaultTCPMSS * 2 * kNumberOfAcks);
 310   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 311
 312   // Lose one more than the congestion window reduction, so that after loss,
 313   // bytes_in_flight is lesser than the congestion window.
 314   size_t send_window_after_loss = kRenoBeta * expected_send_window;
 315   size_t num_packets_to_lose =
 316       (expected_send_window - send_window_after_loss) / kDefaultTCPMSS + 1;
 317   LoseNPackets(num_packets_to_lose);
 318   // Immediately after the loss, ensure at least one packet can be sent.
 319   // Losses without subsequent acks can occur with timer based loss detection.
 320   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(), bytes_in_flight_,
 321                                      HAS_RETRANSMITTABLE_DATA).IsZero());
 322   AckNPackets(1);
 323
 324   // We should now have fallen out of slow start with a reduced window.
 325   expected_send_window *= kRenoBeta;
 326   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 327
 328   // Only 2 packets should be allowed to be sent, per PRR-SSRB.
 329   EXPECT_EQ(2, SendAvailableSendWindow());
 330
 331   // Ack the next packet, which triggers another loss.
 332   LoseNPackets(1);
 333   AckNPackets(1);
 334
 335   // Send 2 packets to simulate PRR-SSRB.
 336   EXPECT_EQ(2, SendAvailableSendWindow());
 337
 338   // Ack the next packet, which triggers another loss.
 339   LoseNPackets(1);
 340   AckNPackets(1);
 341
 342   // Send 2 packets to simulate PRR-SSRB.
 343   EXPECT_EQ(2, SendAvailableSendWindow());
 344
 345   // Exit recovery and return to sending at the new rate.
 346   for (int i = 0; i < kNumberOfAcks; ++i) {
 347     AckNPackets(1);
 348     EXPECT_EQ(1, SendAvailableSendWindow());
 349   }
 350 }
 351
 352 TEST_F(TcpCubicBytesSenderTest, RTOCongestionWindow) {
 353   EXPECT_EQ(kDefaultWindowTCP, sender_->GetCongestionWindow());
 354   // Expect the window to decrease to the minimum once the RTO fires and slow
 355   // start threshold to be set to 1/2 of the CWND.
 356   sender_->OnRetransmissionTimeout(true);
 357   EXPECT_EQ(2 * kDefaultTCPMSS, sender_->GetCongestionWindow());
 358   EXPECT_EQ(5u * kDefaultTCPMSS, sender_->GetSlowStartThreshold());
 359 }
 360
 361 TEST_F(TcpCubicBytesSenderTest, RTOCongestionWindowNoRetransmission) {
 362   EXPECT_EQ(kDefaultWindowTCP, sender_->GetCongestionWindow());
 363
 364   // Expect the window to remain unchanged if the RTO fires but no packets are
 365   // retransmitted.
 366   sender_->OnRetransmissionTimeout(false);
 367   EXPECT_EQ(kDefaultWindowTCP, sender_->GetCongestionWindow());
 368 }
 369
 370 TEST_F(TcpCubicBytesSenderTest, RetransmissionDelay) {
 371   const int64 kRttMs = 10;
 372   const int64 kDeviationMs = 3;
 373   EXPECT_EQ(QuicTime::Delta::Zero(), sender_->RetransmissionDelay());
 374
 375   sender_->rtt_stats_.UpdateRtt(QuicTime::Delta::FromMilliseconds(kRttMs),
 376                                 QuicTime::Delta::Zero(), clock_.Now());
 377
 378   // Initial value is to set the median deviation to half of the initial rtt,
 379   // the median in then multiplied by a factor of 4 and finally the smoothed rtt
 380   // is added which is the initial rtt.
 381   QuicTime::Delta expected_delay =
 382       QuicTime::Delta::FromMilliseconds(kRttMs + kRttMs / 2 * 4);
 383   EXPECT_EQ(expected_delay, sender_->RetransmissionDelay());
 384
 385   for (int i = 0; i < 100; ++i) {
 386     // Run to make sure that we converge.
 387     sender_->rtt_stats_.UpdateRtt(
 388         QuicTime::Delta::FromMilliseconds(kRttMs + kDeviationMs),
 389         QuicTime::Delta::Zero(), clock_.Now());
 390     sender_->rtt_stats_.UpdateRtt(
 391         QuicTime::Delta::FromMilliseconds(kRttMs - kDeviationMs),
 392         QuicTime::Delta::Zero(), clock_.Now());
 393   }
 394   expected_delay = QuicTime::Delta::FromMilliseconds(kRttMs + kDeviationMs * 4);
 395
 396   EXPECT_NEAR(kRttMs, sender_->rtt_stats_.smoothed_rtt().ToMilliseconds(), 1);
 397   EXPECT_NEAR(expected_delay.ToMilliseconds(),
 398               sender_->RetransmissionDelay().ToMilliseconds(), 1);
 399   EXPECT_EQ(
 400       static_cast<int64>(sender_->GetCongestionWindow() * kNumMicrosPerSecond /
 401                          sender_->rtt_stats_.smoothed_rtt().ToMicroseconds()),
 402       sender_->BandwidthEstimate().ToBytesPerSecond());
 403 }
 404
 405 TEST_F(TcpCubicBytesSenderTest, MultipleLossesInOneWindow) {
 406   SendAvailableSendWindow();
 407   const QuicByteCount initial_window = sender_->GetCongestionWindow();
 408   LosePacket(acked_sequence_number_ + 1);
 409   const QuicByteCount post_loss_window = sender_->GetCongestionWindow();
 410   EXPECT_GT(initial_window, post_loss_window);
 411   LosePacket(acked_sequence_number_ + 3);
 412   EXPECT_EQ(post_loss_window, sender_->GetCongestionWindow());
 413   LosePacket(sequence_number_ - 1);
 414   EXPECT_EQ(post_loss_window, sender_->GetCongestionWindow());
 415
 416   // Lose a later packet and ensure the window decreases.
 417   LosePacket(sequence_number_);
 418   EXPECT_GT(post_loss_window, sender_->GetCongestionWindow());
 419 }
 420
 421 TEST_F(TcpCubicBytesSenderTest, DontTrackAckPackets) {
 422   // Send a packet with no retransmittable data, and ensure it's not tracked.
 423   EXPECT_FALSE(sender_->OnPacketSent(clock_.Now(), bytes_in_flight_,
 424                                      sequence_number_++, kDefaultTCPMSS,
 425                                      NO_RETRANSMITTABLE_DATA));
 426
 427   // Send a data packet with retransmittable data, and ensure it is tracked.
 428   EXPECT_TRUE(sender_->OnPacketSent(clock_.Now(), bytes_in_flight_,
 429                                     sequence_number_++, kDefaultTCPMSS,
 430                                     HAS_RETRANSMITTABLE_DATA));
 431 }
 432
 433 TEST_F(TcpCubicBytesSenderTest, ConfigureMaxInitialWindow) {
 434   QuicConfig config;
 435
 436   // Verify that kCOPT: kIW10 forces the congestion window to the default of 10.
 437   QuicTagVector options;
 438   options.push_back(kIW10);
 439   QuicConfigPeer::SetReceivedConnectionOptions(&config, options);
 440   sender_->SetFromConfig(config, Perspective::IS_SERVER);
 441   EXPECT_EQ(10u * kDefaultTCPMSS, sender_->GetCongestionWindow());
 442 }
 443
 444 TEST_F(TcpCubicBytesSenderTest, 2ConnectionCongestionAvoidanceAtEndOfRecovery) {
 445   sender_->SetNumEmulatedConnections(2);
 446   // Ack 10 packets in 5 acks to raise the CWND to 20.
 447   const int kNumberOfAcks = 5;
 448   for (int i = 0; i < kNumberOfAcks; ++i) {
 449     // Send our full send window.
 450     SendAvailableSendWindow();
 451     AckNPackets(2);
 452   }
 453   SendAvailableSendWindow();
 454   QuicByteCount expected_send_window =
 455       kDefaultWindowTCP + (kDefaultTCPMSS * 2 * kNumberOfAcks);
 456   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 457
 458   LoseNPackets(1);
 459
 460   // We should now have fallen out of slow start with a reduced window.
 461   expected_send_window = expected_send_window * sender_->GetRenoBeta();
 462   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 463
 464   // No congestion window growth should occur in recovery phase, i.e., until the
 465   // currently outstanding 20 packets are acked.
 466   for (int i = 0; i < 10; ++i) {
 467     // Send our full send window.
 468     SendAvailableSendWindow();
 469     EXPECT_TRUE(sender_->InRecovery());
 470     AckNPackets(2);
 471     EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 472   }
 473   EXPECT_FALSE(sender_->InRecovery());
 474
 475   // Out of recovery now. Congestion window should not grow for half an RTT.
 476   size_t packets_in_send_window = expected_send_window / kDefaultTCPMSS;
 477   SendAvailableSendWindow();
 478   AckNPackets(packets_in_send_window / 2 - 2);
 479   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 480
 481   // Next ack should increase congestion window by 1MSS.
 482   SendAvailableSendWindow();
 483   AckNPackets(2);
 484   expected_send_window += kDefaultTCPMSS;
 485   packets_in_send_window += 1;
 486   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 487
 488   // Congestion window should remain steady again for half an RTT.
 489   SendAvailableSendWindow();
 490   AckNPackets(packets_in_send_window / 2 - 1);
 491   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 492
 493   // Next ack should cause congestion window to grow by 1MSS.
 494   SendAvailableSendWindow();
 495   AckNPackets(2);
 496   expected_send_window += kDefaultTCPMSS;
 497   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 498 }
 499
 500 TEST_F(TcpCubicBytesSenderTest, 1ConnectionCongestionAvoidanceAtEndOfRecovery) {
 501   sender_->SetNumEmulatedConnections(1);
 502   // Ack 10 packets in 5 acks to raise the CWND to 20.
 503   const int kNumberOfAcks = 5;
 504   for (int i = 0; i < kNumberOfAcks; ++i) {
 505     // Send our full send window.
 506     SendAvailableSendWindow();
 507     AckNPackets(2);
 508   }
 509   SendAvailableSendWindow();
 510   QuicByteCount expected_send_window =
 511       kDefaultWindowTCP + (kDefaultTCPMSS * 2 * kNumberOfAcks);
 512   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 513
 514   LoseNPackets(1);
 515
 516   // We should now have fallen out of slow start with a reduced window.
 517   expected_send_window *= kRenoBeta;
 518   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 519
 520   // No congestion window growth should occur in recovery phase, i.e., until the
 521   // currently outstanding 20 packets are acked.
 522   for (int i = 0; i < 10; ++i) {
 523     // Send our full send window.
 524     SendAvailableSendWindow();
 525     EXPECT_TRUE(sender_->InRecovery());
 526     AckNPackets(2);
 527     EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 528   }
 529   EXPECT_FALSE(sender_->InRecovery());
 530
 531   // Out of recovery now. Congestion window should not grow during RTT.
 532   for (uint64 i = 0; i < expected_send_window / kDefaultTCPMSS - 2; i += 2) {
 533     // Send our full send window.
 534     SendAvailableSendWindow();
 535     AckNPackets(2);
 536     EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 537   }
 538
 539   // Next ack should cause congestion window to grow by 1MSS.
 540   SendAvailableSendWindow();
 541   AckNPackets(2);
 542   expected_send_window += kDefaultTCPMSS;
 543   EXPECT_EQ(expected_send_window, sender_->GetCongestionWindow());
 544 }
 545
 546 TEST_F(TcpCubicBytesSenderTest, BandwidthResumption) {
 547   // Test that when provided with CachedNetworkParameters and opted in to the
 548   // bandwidth resumption experiment, that the TcpCubicSender sets initial CWND
 549   // appropriately.
 550
 551   // Set some common values.
 552   CachedNetworkParameters cached_network_params;
 553   const QuicPacketCount kNumberOfPackets = 123;
 554   const int kBandwidthEstimateBytesPerSecond =
 555       kNumberOfPackets * kDefaultTCPMSS;
 556   cached_network_params.set_bandwidth_estimate_bytes_per_second(
 557       kBandwidthEstimateBytesPerSecond);
 558   cached_network_params.set_min_rtt_ms(1000);
 559
 560   // Make sure that a bandwidth estimate results in a changed CWND.
 561   cached_network_params.set_timestamp(clock_.WallNow().ToUNIXSeconds() -
 562                                       (kNumSecondsPerHour - 1));
 563   sender_->ResumeConnectionState(cached_network_params, false);
 564   EXPECT_EQ(kNumberOfPackets * kDefaultTCPMSS, sender_->GetCongestionWindow());
 565
 566   // Resumed CWND is limited to be in a sensible range.
 567   cached_network_params.set_bandwidth_estimate_bytes_per_second(
 568       (kMaxCongestionWindow + 1) * kDefaultTCPMSS);
 569   sender_->ResumeConnectionState(cached_network_params, false);
 570   EXPECT_EQ(kMaxCongestionWindow * kDefaultTCPMSS,
 571             sender_->GetCongestionWindow());
 572
 573   cached_network_params.set_bandwidth_estimate_bytes_per_second(
 574       (kMinCongestionWindowForBandwidthResumption - 1) * kDefaultTCPMSS);
 575   sender_->ResumeConnectionState(cached_network_params, false);
 576   EXPECT_EQ(kMinCongestionWindowForBandwidthResumption * kDefaultTCPMSS,
 577             sender_->GetCongestionWindow());
 578
 579   // Resume to the max value.
 580   cached_network_params.set_max_bandwidth_estimate_bytes_per_second(
 581       (kMinCongestionWindowForBandwidthResumption + 10) * kDefaultTCPMSS);
 582   sender_->ResumeConnectionState(cached_network_params, true);
 583   EXPECT_EQ((kMinCongestionWindowForBandwidthResumption + 10) * kDefaultTCPMSS,
 584             sender_->GetCongestionWindow());
 585 }
 586
 587 TEST_F(TcpCubicBytesSenderTest, PaceBelowCWND) {
 588   QuicConfig config;
 589
 590   // Verify that kCOPT: kMIN4 forces the min CWND to 1 packet, but allows up
 591   // to 4 to be sent.
 592   QuicTagVector options;
 593   options.push_back(kMIN4);
 594   QuicConfigPeer::SetReceivedConnectionOptions(&config, options);
 595   sender_->SetFromConfig(config, Perspective::IS_SERVER);
 596   sender_->OnRetransmissionTimeout(true);
 597   EXPECT_EQ(kDefaultTCPMSS, sender_->GetCongestionWindow());
 598   EXPECT_TRUE(sender_->TimeUntilSend(QuicTime::Zero(), kDefaultTCPMSS,
 599                                      HAS_RETRANSMITTABLE_DATA).IsZero());
 600   EXPECT_TRUE(sender_->TimeUntilSend(QuicTime::Zero(), 2 * kDefaultTCPMSS,
 601                                      HAS_RETRANSMITTABLE_DATA).IsZero());
 602   EXPECT_TRUE(sender_->TimeUntilSend(QuicTime::Zero(), 3 * kDefaultTCPMSS,
 603                                      HAS_RETRANSMITTABLE_DATA).IsZero());
 604   EXPECT_FALSE(sender_->TimeUntilSend(QuicTime::Zero(), 4 * kDefaultTCPMSS,
 605                                       HAS_RETRANSMITTABLE_DATA).IsZero());
 606 }
 607
 608 }  // namespace test
 609 }  // namespace net