src/media/cast/congestion_control/congestion_control_unittest.cc

   1 // Copyright 2013 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/test/simple_test_tick_clock.h"
   6 #include "media/cast/cast_defines.h"
   7 #include "media/cast/congestion_control/congestion_control.h"
   8 #include "testing/gtest/include/gtest/gtest.h"
   9
  10 namespace media {
  11 namespace cast {
  12
  13 static const uint32 kMaxBitrateConfigured = 5000000;
  14 static const uint32 kMinBitrateConfigured = 500000;
  15 static const uint32 kStartBitrate = 2000000;
  16 static const int64 kStartMillisecond = GG_INT64_C(12345678900000);
  17 static const int64 kRttMs = 20;
  18 static const int64 kAckRateMs = 33;
  19
  20 class CongestionControlTest : public ::testing::Test {
  21  protected:
  22   CongestionControlTest()
  23       : congestion_control_(&testing_clock_,
  24                             kDefaultCongestionControlBackOff,
  25                             kMaxBitrateConfigured,
  26                             kMinBitrateConfigured,
  27                             kStartBitrate) {
  28     testing_clock_.Advance(
  29         base::TimeDelta::FromMilliseconds(kStartMillisecond));
  30   }
  31
  32   base::SimpleTestTickClock testing_clock_;
  33   CongestionControl congestion_control_;
  34 };
  35
  36 TEST_F(CongestionControlTest, Max) {
  37   uint32 new_bitrate = 0;
  38   base::TimeDelta rtt = base::TimeDelta::FromMilliseconds(kRttMs);
  39   base::TimeDelta ack_rate = base::TimeDelta::FromMilliseconds(kAckRateMs);
  40   EXPECT_FALSE(congestion_control_.OnAck(rtt, &new_bitrate));
  41
  42   uint32 expected_increase_bitrate = 0;
  43
  44   // Expected time is 5 seconds. 500000 - 2000000 = 5 * 1500 * 8 * (1000 / 20).
  45   for (int i = 0; i < 151; ++i) {
  46     testing_clock_.Advance(ack_rate);
  47     EXPECT_TRUE(congestion_control_.OnAck(rtt, &new_bitrate));
  48     expected_increase_bitrate += 1500 * 8 * kAckRateMs / kRttMs;
  49     EXPECT_EQ(kStartBitrate + expected_increase_bitrate, new_bitrate);
  50   }
  51   testing_clock_.Advance(ack_rate);
  52   EXPECT_TRUE(congestion_control_.OnAck(rtt, &new_bitrate));
  53   EXPECT_EQ(kMaxBitrateConfigured, new_bitrate);
  54 }
  55
  56 TEST_F(CongestionControlTest, Min) {
  57   uint32 new_bitrate = 0;
  58   base::TimeDelta rtt = base::TimeDelta::FromMilliseconds(kRttMs);
  59   base::TimeDelta ack_rate = base::TimeDelta::FromMilliseconds(kAckRateMs);
  60   EXPECT_FALSE(congestion_control_.OnNack(rtt, &new_bitrate));
  61
  62   uint32 expected_decrease_bitrate = kStartBitrate;
  63
  64   // Expected number is 10. 2000 * 0.875^10 <= 500.
  65   for (int i = 0; i < 10; ++i) {
  66     testing_clock_.Advance(ack_rate);
  67      EXPECT_TRUE(congestion_control_.OnNack(rtt, &new_bitrate));
  68      expected_decrease_bitrate = static_cast<uint32>(
  69          expected_decrease_bitrate * kDefaultCongestionControlBackOff);
  70      EXPECT_EQ(expected_decrease_bitrate, new_bitrate);
  71    }
  72    testing_clock_.Advance(ack_rate);
  73    EXPECT_TRUE(congestion_control_.OnNack(rtt, &new_bitrate));
  74    EXPECT_EQ(kMinBitrateConfigured, new_bitrate);
  75 }
  76
  77 TEST_F(CongestionControlTest, Timing) {
  78   base::TimeDelta rtt = base::TimeDelta::FromMilliseconds(kRttMs);
  79   base::TimeDelta ack_rate = base::TimeDelta::FromMilliseconds(kAckRateMs);
  80   uint32 new_bitrate = 0;
  81   uint32 expected_bitrate = kStartBitrate;
  82
  83   EXPECT_FALSE(congestion_control_.OnAck(rtt, &new_bitrate));
  84
  85   testing_clock_.Advance(ack_rate);
  86   EXPECT_TRUE(congestion_control_.OnAck(rtt, &new_bitrate));
  87   expected_bitrate += 1500 * 8 * kAckRateMs / kRttMs;
  88   EXPECT_EQ(expected_bitrate, new_bitrate);
  89
  90   // We should back immediately.
  91   EXPECT_TRUE(congestion_control_.OnNack(rtt, &new_bitrate));
  92   expected_bitrate = static_cast<uint32>(
  93       expected_bitrate * kDefaultCongestionControlBackOff);
  94   EXPECT_EQ(expected_bitrate, new_bitrate);
  95
  96   // Less than one RTT have passed don't back again.
  97   testing_clock_.Advance(base::TimeDelta::FromMilliseconds(10));
  98   EXPECT_FALSE(congestion_control_.OnNack(rtt, &new_bitrate));
  99
 100   testing_clock_.Advance(base::TimeDelta::FromMilliseconds(10));
 101   EXPECT_TRUE(congestion_control_.OnNack(rtt, &new_bitrate));
 102   expected_bitrate = static_cast<uint32>(
 103       expected_bitrate * kDefaultCongestionControlBackOff);
 104   EXPECT_EQ(expected_bitrate, new_bitrate);
 105
 106   testing_clock_.Advance(base::TimeDelta::FromMilliseconds(10));
 107   EXPECT_FALSE(congestion_control_.OnAck(rtt, &new_bitrate));
 108   testing_clock_.Advance(base::TimeDelta::FromMilliseconds(10));
 109   EXPECT_TRUE(congestion_control_.OnAck(rtt, &new_bitrate));
 110   expected_bitrate += 1500 * 8 * 20 / kRttMs;
 111   EXPECT_EQ(expected_bitrate, new_bitrate);
 112
 113   testing_clock_.Advance(base::TimeDelta::FromMilliseconds(10));
 114   EXPECT_FALSE(congestion_control_.OnAck(rtt, &new_bitrate));
 115   testing_clock_.Advance(base::TimeDelta::FromMilliseconds(10));
 116   EXPECT_TRUE(congestion_control_.OnAck(rtt, &new_bitrate));
 117   expected_bitrate += 1500 * 8 * 20 / kRttMs;
 118   EXPECT_EQ(expected_bitrate, new_bitrate);
 119
 120   // Test long elapsed time (300 ms).
 121   testing_clock_.Advance(base::TimeDelta::FromMilliseconds(300));
 122   EXPECT_TRUE(congestion_control_.OnAck(rtt, &new_bitrate));
 123   expected_bitrate += 1500 * 8 * 100 / kRttMs;
 124   EXPECT_EQ(expected_bitrate, new_bitrate);
 125
 126   // Test many short elapsed time (1 ms).
 127   for (int i = 0; i < 19; ++i) {
 128     testing_clock_.Advance(base::TimeDelta::FromMilliseconds(1));
 129     EXPECT_FALSE(congestion_control_.OnAck(rtt, &new_bitrate));
 130   }
 131   testing_clock_.Advance(base::TimeDelta::FromMilliseconds(1));
 132   EXPECT_TRUE(congestion_control_.OnAck(rtt, &new_bitrate));
 133   expected_bitrate += 1500 * 8 * 20 / kRttMs;
 134   EXPECT_EQ(expected_bitrate, new_bitrate);
 135 }
 136
 137 }  // namespace cast
 138 }  // namespace media