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   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
  29 TEST_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.
  55 TEST_F(HybridSlowStartTest, AckTrain) {
  56   // At a typical RTT 60 ms, assuming that the inter arrival 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
  81 TEST_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