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
11namespace net {
12namespace test {
13
14class HybridSlowStartTest : public ::testing::Test {
15 protected:
16  HybridSlowStartTest()
17     : one_ms_(QuicTime::Delta::FromMilliseconds(1)),
18       rtt_(QuicTime::Delta::FromMilliseconds(60)) {
19  }
20  virtual void SetUp() {
21    slow_start_.reset(new HybridSlowStart(&clock_));
22  }
23  const QuicTime::Delta one_ms_;
24  const QuicTime::Delta rtt_;
25  MockClock clock_;
26  scoped_ptr<HybridSlowStart> slow_start_;
27};
28
29TEST_F(HybridSlowStartTest, Simple) {
30  QuicPacketSequenceNumber sequence_number = 1;
31  QuicPacketSequenceNumber end_sequence_number = 3;
32  slow_start_->StartReceiveRound(end_sequence_number);
33
34  EXPECT_FALSE(slow_start_->IsEndOfRound(sequence_number++));
35
36  // Test duplicates.
37  EXPECT_FALSE(slow_start_->IsEndOfRound(sequence_number));
38
39  EXPECT_FALSE(slow_start_->IsEndOfRound(sequence_number++));
40  EXPECT_TRUE(slow_start_->IsEndOfRound(sequence_number++));
41
42  // Test without a new registered end_sequence_number;
43  EXPECT_TRUE(slow_start_->IsEndOfRound(sequence_number++));
44
45  end_sequence_number = 20;
46  slow_start_->StartReceiveRound(end_sequence_number);
47  while (sequence_number < end_sequence_number) {
48    EXPECT_FALSE(slow_start_->IsEndOfRound(sequence_number++));
49  }
50  EXPECT_TRUE(slow_start_->IsEndOfRound(sequence_number++));
51}
52
53// TODO(ianswett): Add tests which more realistically invoke the methods,
54// simulating how actual acks arrive and packets are sent.
55TEST_F(HybridSlowStartTest, AckTrain) {
56  // At a typical RTT 60 ms, assuming that the inter arrival timestamp is 1 ms,
57  // we expect to be able to send a burst of 30 packet before we trigger the
58  // ack train detection.
59  const int kMaxLoopCount = 5;
60  QuicPacketSequenceNumber sequence_number = 2;
61  QuicPacketSequenceNumber end_sequence_number = 2;
62  for (int burst = 0; burst < kMaxLoopCount; ++burst) {
63    slow_start_->StartReceiveRound(end_sequence_number);
64    do {
65      clock_.AdvanceTime(one_ms_);
66      EXPECT_FALSE(slow_start_->ShouldExitSlowStart(rtt_, rtt_, 100));
67    }  while (!slow_start_->IsEndOfRound(sequence_number++));
68    end_sequence_number *= 2;  // Exponential growth.
69  }
70  slow_start_->StartReceiveRound(end_sequence_number);
71
72  for (int n = 0;
73       n < 29 && !slow_start_->IsEndOfRound(sequence_number++); ++n) {
74    clock_.AdvanceTime(one_ms_);
75    EXPECT_FALSE(slow_start_->ShouldExitSlowStart(rtt_, rtt_, 100));
76  }
77  clock_.AdvanceTime(one_ms_);
78  EXPECT_TRUE(slow_start_->ShouldExitSlowStart(rtt_, rtt_, 100));
79}
80
81TEST_F(HybridSlowStartTest, Delay) {
82  // We expect to detect the increase at +1/16 of the RTT; hence at a typical
83  // RTT of 60ms the detection will happen at 63.75 ms.
84  const int kHybridStartMinSamples = 8;  // Number of acks required to trigger.
85
86  QuicPacketSequenceNumber end_sequence_number = 1;
87  slow_start_->StartReceiveRound(end_sequence_number++);
88
89  // Will not trigger since our lowest RTT in our burst is the same as the long
90  // term RTT provided.
91  for (int n = 0; n < kHybridStartMinSamples; ++n) {
92    EXPECT_FALSE(slow_start_->ShouldExitSlowStart(
93        rtt_.Add(QuicTime::Delta::FromMilliseconds(n)), rtt_, 100));
94  }
95  slow_start_->StartReceiveRound(end_sequence_number++);
96  for (int n = 1; n < kHybridStartMinSamples; ++n) {
97    EXPECT_FALSE(slow_start_->ShouldExitSlowStart(
98        rtt_.Add(QuicTime::Delta::FromMilliseconds(n + 5)), rtt_, 100));
99  }
100  // Expect to trigger since all packets in this burst was above the long term
101  // RTT provided.
102  EXPECT_TRUE(slow_start_->ShouldExitSlowStart(
103      rtt_.Add(QuicTime::Delta::FromMilliseconds(5)), rtt_, 100));
104}
105
106}  // namespace test
107}  // namespace net
108