net/quic/congestion_control/hybrid_slow_start_test.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 "base/logging.h"
   6 #include "base/memory/scoped_ptr.h"
   7 #include "net/quic/congestion_control/hybrid_slow_start.h"
   8 #include "net/quic/test_tools/mock_clock.h"
   9 #include "testing/gtest/include/gtest/gtest.h"
  10
  11 namespace net {
  12 namespace test {
  13
  14 class HybridSlowStartTest : public ::testing::Test {
  15  protected:
  16   HybridSlowStartTest()
  17      : one_ms_(QuicTime::Delta::FromMilliseconds(1)),
  18        rtt_(QuicTime::Delta::FromMilliseconds(60)) {
  19   }
  20   void SetUp() override { slow_start_.reset(new HybridSlowStart(&clock_)); }
  21   const QuicTime::Delta one_ms_;
  22   const QuicTime::Delta rtt_;
  23   MockClock clock_;
  24   scoped_ptr<HybridSlowStart> slow_start_;
  25 };
  26
  27 TEST_F(HybridSlowStartTest, Simple) {
  28   QuicPacketSequenceNumber sequence_number = 1;
  29   QuicPacketSequenceNumber end_sequence_number = 3;
  30   slow_start_->StartReceiveRound(end_sequence_number);
  31
  32   EXPECT_FALSE(slow_start_->IsEndOfRound(sequence_number++));
  33
  34   // Test duplicates.
  35   EXPECT_FALSE(slow_start_->IsEndOfRound(sequence_number));
  36
  37   EXPECT_FALSE(slow_start_->IsEndOfRound(sequence_number++));
  38   EXPECT_TRUE(slow_start_->IsEndOfRound(sequence_number++));
  39
  40   // Test without a new registered end_sequence_number;
  41   EXPECT_TRUE(slow_start_->IsEndOfRound(sequence_number++));
  42
  43   end_sequence_number = 20;
  44   slow_start_->StartReceiveRound(end_sequence_number);
  45   while (sequence_number < end_sequence_number) {
  46     EXPECT_FALSE(slow_start_->IsEndOfRound(sequence_number++));
  47   }
  48   EXPECT_TRUE(slow_start_->IsEndOfRound(sequence_number++));
  49 }
  50
  51 // TODO(ianswett): Add tests which more realistically invoke the methods,
  52 // simulating how actual acks arrive and packets are sent.
  53 TEST_F(HybridSlowStartTest, AckTrain) {
  54   // At a typical RTT 60 ms, assuming that the inter arrival timestamp is 1 ms,
  55   // we expect to be able to send a burst of 30 packet before we trigger the
  56   // ack train detection.
  57   // Run this test for both enabled and disabled ack train detection.
  58   for (int i = 0; i < 2; ++i) {
  59     const bool ack_train_detection = (i == 1);
  60     slow_start_->set_ack_train_detection(ack_train_detection);
  61
  62     const int kMaxLoopCount = 5;
  63     QuicPacketSequenceNumber sequence_number = 2;
  64     QuicPacketSequenceNumber end_sequence_number = 2;
  65     for (int burst = 0; burst < kMaxLoopCount; ++burst) {
  66       slow_start_->StartReceiveRound(end_sequence_number);
  67       do {
  68         clock_.AdvanceTime(one_ms_);
  69         EXPECT_FALSE(slow_start_->ShouldExitSlowStart(rtt_, rtt_, 100));
  70       } while (!slow_start_->IsEndOfRound(sequence_number++));
  71       end_sequence_number *= 2;  // Exponential growth.
  72     }
  73     slow_start_->StartReceiveRound(end_sequence_number);
  74
  75     for (int n = 0;
  76          n < 29 && !slow_start_->IsEndOfRound(sequence_number++); ++n) {
  77       clock_.AdvanceTime(one_ms_);
  78       EXPECT_FALSE(slow_start_->ShouldExitSlowStart(rtt_, rtt_, 100));
  79     }
  80     clock_.AdvanceTime(one_ms_);
  81     EXPECT_EQ(ack_train_detection,
  82               slow_start_->ShouldExitSlowStart(rtt_, rtt_, 100));
  83   }
  84 }
  85
  86 TEST_F(HybridSlowStartTest, Delay) {
  87   // We expect to detect the increase at +1/8 of the RTT; hence at a typical
  88   // RTT of 60ms the detection will happen at 67.5 ms.
  89   const int kHybridStartMinSamples = 8;  // Number of acks required to trigger.
  90
  91   QuicPacketSequenceNumber end_sequence_number = 1;
  92   slow_start_->StartReceiveRound(end_sequence_number++);
  93
  94   // Will not trigger since our lowest RTT in our burst is the same as the long
  95   // term RTT provided.
  96   for (int n = 0; n < kHybridStartMinSamples; ++n) {
  97     EXPECT_FALSE(slow_start_->ShouldExitSlowStart(
  98         rtt_.Add(QuicTime::Delta::FromMilliseconds(n)), rtt_, 100));
  99   }
 100   slow_start_->StartReceiveRound(end_sequence_number++);
 101   for (int n = 1; n < kHybridStartMinSamples; ++n) {
 102     EXPECT_FALSE(slow_start_->ShouldExitSlowStart(
 103         rtt_.Add(QuicTime::Delta::FromMilliseconds(n + 10)), rtt_, 100));
 104   }
 105   // Expect to trigger since all packets in this burst was above the long term
 106   // RTT provided.
 107   EXPECT_TRUE(slow_start_->ShouldExitSlowStart(
 108       rtt_.Add(QuicTime::Delta::FromMilliseconds(10)), rtt_, 100));
 109 }
 110
 111 }  // namespace test
 112 }  // namespace net