net/quic/congestion_control/tcp_cubic_sender_test.cc - platform/external/chromium_org - Git at Google

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "net/quic/congestion_control/tcp_cubic_sender.h"
 #include "net/quic/congestion_control/tcp_receiver.h"
 #include "net/quic/test_tools/mock_clock.h"
 #include "testing/gtest/include/gtest/gtest.h"

 namespace net {
 namespace test {

 const uint32 kDefaultWindowTCP = 10 * kMaxPacketSize;
 const QuicByteCount kNoNBytesInFlight = 0;

 class TcpCubicSenderPeer : public TcpCubicSender {
  public:
   // TODO(ianswett): Remove 10000 once b/10075719 is fixed.
   TcpCubicSenderPeer(const QuicClock* clock, bool reno)
       : TcpCubicSender(clock, reno, 10000) {
   }
   using TcpCubicSender::AvailableCongestionWindow;
   using TcpCubicSender::CongestionWindow;
   using TcpCubicSender::AckAccounting;
 };

 class TcpCubicSenderTest : public ::testing::Test {
  protected:
   TcpCubicSenderTest()
      : rtt_(QuicTime::Delta::FromMilliseconds(60)),
        one_ms_(QuicTime::Delta::FromMilliseconds(1)),
        sender_(new TcpCubicSenderPeer(&clock_, true)),
        receiver_(new TcpReceiver()),
        sequence_number_(1),
        acked_sequence_number_(0) {
   }

   void SendAvailableCongestionWindow() {
     QuicByteCount bytes_to_send = sender_->AvailableCongestionWindow();
     while (bytes_to_send > 0) {
       QuicByteCount bytes_in_packet = std::min(kMaxPacketSize, bytes_to_send);
       sender_->SentPacket(clock_.Now(), sequence_number_++, bytes_in_packet,
                           NOT_RETRANSMISSION);
       bytes_to_send -= bytes_in_packet;
       if (bytes_to_send > 0) {
         EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(), NOT_RETRANSMISSION,
                         HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());
       }
     }
   }
   // Normal is that TCP acks every other segment.
   void AckNPackets(int n) {
     for (int i = 0; i < n; ++i) {
       acked_sequence_number_++;
       sender_->OnIncomingAck(acked_sequence_number_, kMaxPacketSize, rtt_);
     }
     clock_.AdvanceTime(one_ms_);  // 1 millisecond.
   }

   const QuicTime::Delta rtt_;
   const QuicTime::Delta one_ms_;
   MockClock clock_;
   SendAlgorithmInterface::SentPacketsMap not_used_;
   scoped_ptr<TcpCubicSenderPeer> sender_;
   scoped_ptr<TcpReceiver> receiver_;
   QuicPacketSequenceNumber sequence_number_;
   QuicPacketSequenceNumber acked_sequence_number_;
 };

 TEST_F(TcpCubicSenderTest, SimpleSender) {
   QuicCongestionFeedbackFrame feedback;
   // At startup make sure we are at the default.
   EXPECT_EQ(kDefaultWindowTCP,
             sender_->AvailableCongestionWindow());
   // At startup make sure we can send.
   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(),
       NOT_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());
   // Get default QuicCongestionFeedbackFrame from receiver.
   ASSERT_TRUE(receiver_->GenerateCongestionFeedback(&feedback));
   sender_->OnIncomingQuicCongestionFeedbackFrame(feedback, clock_.Now(),
                                                  not_used_);
   // Make sure we can send.
   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(),
       NOT_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());
   // And that window is un-affected.
   EXPECT_EQ(kDefaultWindowTCP, sender_->AvailableCongestionWindow());

   // A retransmitt should always retun 0.
   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(),
       IS_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());
 }

 TEST_F(TcpCubicSenderTest, ExponentialSlowStart) {
   const int kNumberOfAck = 20;
   QuicCongestionFeedbackFrame feedback;
   // At startup make sure we can send.
   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(),
       NOT_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());
   // Get default QuicCongestionFeedbackFrame from receiver.
   ASSERT_TRUE(receiver_->GenerateCongestionFeedback(&feedback));
   sender_->OnIncomingQuicCongestionFeedbackFrame(feedback, clock_.Now(),
                                                  not_used_);
   // Make sure we can send.
   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(),
       NOT_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());

   for (int n = 0; n < kNumberOfAck; ++n) {
     // Send our full congestion window.
     SendAvailableCongestionWindow();
     AckNPackets(2);
   }
   QuicByteCount bytes_to_send = sender_->CongestionWindow();
   EXPECT_EQ(kDefaultWindowTCP + kMaxPacketSize * 2 * kNumberOfAck,
             bytes_to_send);
 }

 TEST_F(TcpCubicSenderTest, SlowStartAckTrain) {
   // Make sure that we fall out of slow start when we send ACK train longer
   // than half the RTT, in this test case 30ms, which is more than 30 calls to
   // Ack2Packets in one round.
   // Since we start at 10 packet first round will be 5 second round 10 etc
   // Hence we should pass 30 at 65 = 5 + 10 + 20 + 30
   const int kNumberOfAck = 65;
   QuicCongestionFeedbackFrame feedback;
   // At startup make sure we can send.
   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(),
       NOT_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());
   // Get default QuicCongestionFeedbackFrame from receiver.
   ASSERT_TRUE(receiver_->GenerateCongestionFeedback(&feedback));
   sender_->OnIncomingQuicCongestionFeedbackFrame(feedback, clock_.Now(),
                                                  not_used_);
   // Make sure we can send.
   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(),
       NOT_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());

   for (int n = 0; n < kNumberOfAck; ++n) {
     // Send our full congestion window.
     SendAvailableCongestionWindow();
     AckNPackets(2);
   }
   QuicByteCount expected_congestion_window =
       kDefaultWindowTCP + (kMaxPacketSize * 2 * kNumberOfAck);
   EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());
   // We should now have fallen out of slow start.
   SendAvailableCongestionWindow();
   AckNPackets(2);
   expected_congestion_window += kMaxPacketSize;
   EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());

   // Testing Reno phase.
   // We should need 141(65*2+1+10) ACK:ed packets before increasing window by
   // one.
   for (int m = 0; m < 70; ++m) {
     SendAvailableCongestionWindow();
     AckNPackets(2);
     EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());
   }
   SendAvailableCongestionWindow();
   AckNPackets(2);
   expected_congestion_window += kMaxPacketSize;
   EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());
 }

 TEST_F(TcpCubicSenderTest, SlowStartPacketLoss) {
   // Make sure that we fall out of slow start when we encounter a packet loss.
   const int kNumberOfAck = 10;
   QuicCongestionFeedbackFrame feedback;
   // At startup make sure we can send.
   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(),
       NOT_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());
   // Get default QuicCongestionFeedbackFrame from receiver.
   ASSERT_TRUE(receiver_->GenerateCongestionFeedback(&feedback));
   sender_->OnIncomingQuicCongestionFeedbackFrame(feedback, clock_.Now(),
                                                  not_used_);
   // Make sure we can send.
   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(),
       NOT_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());

   for (int i = 0; i < kNumberOfAck; ++i) {
     // Send our full congestion window.
     SendAvailableCongestionWindow();
     AckNPackets(2);
   }
   SendAvailableCongestionWindow();
   QuicByteCount expected_congestion_window = kDefaultWindowTCP +
       (kMaxPacketSize * 2 * kNumberOfAck);
   EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());

   sender_->OnIncomingLoss(clock_.Now());

   // Make sure that we should not send right now.
   EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(), NOT_RETRANSMISSION,
       HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsInfinite());

   // We should now have fallen out of slow start.
   // We expect window to be cut in half.
   expected_congestion_window /= 2;
   EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());

   // Testing Reno phase.
   // We need to ack half of the pending packet before we can send agin.
   int number_of_packets_in_window = expected_congestion_window / kMaxPacketSize;
   AckNPackets(number_of_packets_in_window);
   EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());
   EXPECT_EQ(0u, sender_->AvailableCongestionWindow());

   AckNPackets(1);
   expected_congestion_window += kMaxPacketSize;
   number_of_packets_in_window++;
   EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());

   // We should need number_of_packets_in_window ACK:ed packets before
   // increasing window by one.
   for (int k = 0; k < number_of_packets_in_window; ++k) {
     SendAvailableCongestionWindow();
     AckNPackets(1);
     EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());
   }
   SendAvailableCongestionWindow();
   AckNPackets(1);
   expected_congestion_window += kMaxPacketSize;
   EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());
 }

 TEST_F(TcpCubicSenderTest, RetransmissionDelay) {
   const int64 kRttMs = 10;
   const int64 kDeviationMs = 3;
   EXPECT_EQ(QuicTime::Delta::Zero(), sender_->RetransmissionDelay());

   sender_->AckAccounting(QuicTime::Delta::FromMilliseconds(kRttMs));

   // Initial value is to set the median deviation to half of the initial
   // rtt, the median in then multiplied by a factor of 4 and finaly the
   // smoothed rtt is added which is the inital rtt.
   QuicTime::Delta expected_delay =
       QuicTime::Delta::FromMilliseconds(kRttMs + kRttMs / 2 * 4);
   EXPECT_EQ(expected_delay, sender_->RetransmissionDelay());

   for (int i = 0; i < 100; ++i) {
     // Run to make sure that we converge.
     sender_->AckAccounting(
         QuicTime::Delta::FromMilliseconds(kRttMs + kDeviationMs));
     sender_->AckAccounting(
         QuicTime::Delta::FromMilliseconds(kRttMs - kDeviationMs));
   }
   expected_delay = QuicTime::Delta::FromMilliseconds(kRttMs + kDeviationMs * 4);

   EXPECT_NEAR(kRttMs, sender_->SmoothedRtt().ToMilliseconds(), 1);
   EXPECT_NEAR(expected_delay.ToMilliseconds(),
               sender_->RetransmissionDelay().ToMilliseconds(),
               1);
 }
 }  // namespace test
 }  // namespace net
	// Copyright (c) 2012 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	#include "base/logging.h"
	#include "base/memory/scoped_ptr.h"
	#include "net/quic/congestion_control/tcp_cubic_sender.h"
	#include "net/quic/congestion_control/tcp_receiver.h"
	#include "net/quic/test_tools/mock_clock.h"
	#include "testing/gtest/include/gtest/gtest.h"

	namespace net {
	namespace test {

	const uint32 kDefaultWindowTCP = 10 * kMaxPacketSize;
	const QuicByteCount kNoNBytesInFlight = 0;

	class TcpCubicSenderPeer : public TcpCubicSender {
	public:
	// TODO(ianswett): Remove 10000 once b/10075719 is fixed.
	TcpCubicSenderPeer(const QuicClock* clock, bool reno)
	: TcpCubicSender(clock, reno, 10000) {
	}
	using TcpCubicSender::AvailableCongestionWindow;
	using TcpCubicSender::CongestionWindow;
	using TcpCubicSender::AckAccounting;
	};

	class TcpCubicSenderTest : public ::testing::Test {
	protected:
	TcpCubicSenderTest()
	: rtt_(QuicTime::Delta::FromMilliseconds(60)),
	one_ms_(QuicTime::Delta::FromMilliseconds(1)),
	sender_(new TcpCubicSenderPeer(&clock_, true)),
	receiver_(new TcpReceiver()),
	sequence_number_(1),
	acked_sequence_number_(0) {
	}

	void SendAvailableCongestionWindow() {
	QuicByteCount bytes_to_send = sender_->AvailableCongestionWindow();
	while (bytes_to_send > 0) {
	QuicByteCount bytes_in_packet = std::min(kMaxPacketSize, bytes_to_send);
	sender_->SentPacket(clock_.Now(), sequence_number_++, bytes_in_packet,
	NOT_RETRANSMISSION);
	bytes_to_send -= bytes_in_packet;
	if (bytes_to_send > 0) {
	EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(), NOT_RETRANSMISSION,
	HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());
	}
	}
	}
	// Normal is that TCP acks every other segment.
	void AckNPackets(int n) {
	for (int i = 0; i < n; ++i) {
	acked_sequence_number_++;
	sender_->OnIncomingAck(acked_sequence_number_, kMaxPacketSize, rtt_);
	}
	clock_.AdvanceTime(one_ms_); // 1 millisecond.
	}

	const QuicTime::Delta rtt_;
	const QuicTime::Delta one_ms_;
	MockClock clock_;
	SendAlgorithmInterface::SentPacketsMap not_used_;
	scoped_ptr<TcpCubicSenderPeer> sender_;
	scoped_ptr<TcpReceiver> receiver_;
	QuicPacketSequenceNumber sequence_number_;
	QuicPacketSequenceNumber acked_sequence_number_;
	};

	TEST_F(TcpCubicSenderTest, SimpleSender) {
	QuicCongestionFeedbackFrame feedback;
	// At startup make sure we are at the default.
	EXPECT_EQ(kDefaultWindowTCP,
	sender_->AvailableCongestionWindow());
	// At startup make sure we can send.
	EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(),
	NOT_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());
	// Get default QuicCongestionFeedbackFrame from receiver.
	ASSERT_TRUE(receiver_->GenerateCongestionFeedback(&feedback));
	sender_->OnIncomingQuicCongestionFeedbackFrame(feedback, clock_.Now(),
	not_used_);
	// Make sure we can send.
	EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(),
	NOT_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());
	// And that window is un-affected.
	EXPECT_EQ(kDefaultWindowTCP, sender_->AvailableCongestionWindow());

	// A retransmitt should always retun 0.
	EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(),
	IS_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());
	}

	TEST_F(TcpCubicSenderTest, ExponentialSlowStart) {
	const int kNumberOfAck = 20;
	QuicCongestionFeedbackFrame feedback;
	// At startup make sure we can send.
	EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(),
	NOT_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());
	// Get default QuicCongestionFeedbackFrame from receiver.
	ASSERT_TRUE(receiver_->GenerateCongestionFeedback(&feedback));
	sender_->OnIncomingQuicCongestionFeedbackFrame(feedback, clock_.Now(),
	not_used_);
	// Make sure we can send.
	EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(),
	NOT_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());

	for (int n = 0; n < kNumberOfAck; ++n) {
	// Send our full congestion window.
	SendAvailableCongestionWindow();
	AckNPackets(2);
	}
	QuicByteCount bytes_to_send = sender_->CongestionWindow();
	EXPECT_EQ(kDefaultWindowTCP + kMaxPacketSize * 2 * kNumberOfAck,
	bytes_to_send);
	}

	TEST_F(TcpCubicSenderTest, SlowStartAckTrain) {
	// Make sure that we fall out of slow start when we send ACK train longer
	// than half the RTT, in this test case 30ms, which is more than 30 calls to
	// Ack2Packets in one round.
	// Since we start at 10 packet first round will be 5 second round 10 etc
	// Hence we should pass 30 at 65 = 5 + 10 + 20 + 30
	const int kNumberOfAck = 65;
	QuicCongestionFeedbackFrame feedback;
	// At startup make sure we can send.
	EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(),
	NOT_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());
	// Get default QuicCongestionFeedbackFrame from receiver.
	ASSERT_TRUE(receiver_->GenerateCongestionFeedback(&feedback));
	sender_->OnIncomingQuicCongestionFeedbackFrame(feedback, clock_.Now(),
	not_used_);
	// Make sure we can send.
	EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(),
	NOT_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());

	for (int n = 0; n < kNumberOfAck; ++n) {
	// Send our full congestion window.
	SendAvailableCongestionWindow();
	AckNPackets(2);
	}
	QuicByteCount expected_congestion_window =
	kDefaultWindowTCP + (kMaxPacketSize * 2 * kNumberOfAck);
	EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());
	// We should now have fallen out of slow start.
	SendAvailableCongestionWindow();
	AckNPackets(2);
	expected_congestion_window += kMaxPacketSize;
	EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());

	// Testing Reno phase.
	// We should need 141(65*2+1+10) ACK:ed packets before increasing window by
	// one.
	for (int m = 0; m < 70; ++m) {
	SendAvailableCongestionWindow();
	AckNPackets(2);
	EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());
	}
	SendAvailableCongestionWindow();
	AckNPackets(2);
	expected_congestion_window += kMaxPacketSize;
	EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());
	}

	TEST_F(TcpCubicSenderTest, SlowStartPacketLoss) {
	// Make sure that we fall out of slow start when we encounter a packet loss.
	const int kNumberOfAck = 10;
	QuicCongestionFeedbackFrame feedback;
	// At startup make sure we can send.
	EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(),
	NOT_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());
	// Get default QuicCongestionFeedbackFrame from receiver.
	ASSERT_TRUE(receiver_->GenerateCongestionFeedback(&feedback));
	sender_->OnIncomingQuicCongestionFeedbackFrame(feedback, clock_.Now(),
	not_used_);
	// Make sure we can send.
	EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(),
	NOT_RETRANSMISSION, HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsZero());

	for (int i = 0; i < kNumberOfAck; ++i) {
	// Send our full congestion window.
	SendAvailableCongestionWindow();
	AckNPackets(2);
	}
	SendAvailableCongestionWindow();
	QuicByteCount expected_congestion_window = kDefaultWindowTCP +
	(kMaxPacketSize * 2 * kNumberOfAck);
	EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());

	sender_->OnIncomingLoss(clock_.Now());

	// Make sure that we should not send right now.
	EXPECT_TRUE(sender_->TimeUntilSend(clock_.Now(), NOT_RETRANSMISSION,
	HAS_RETRANSMITTABLE_DATA, NOT_HANDSHAKE).IsInfinite());

	// We should now have fallen out of slow start.
	// We expect window to be cut in half.
	expected_congestion_window /= 2;
	EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());

	// Testing Reno phase.
	// We need to ack half of the pending packet before we can send agin.
	int number_of_packets_in_window = expected_congestion_window / kMaxPacketSize;
	AckNPackets(number_of_packets_in_window);
	EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());
	EXPECT_EQ(0u, sender_->AvailableCongestionWindow());

	AckNPackets(1);
	expected_congestion_window += kMaxPacketSize;
	number_of_packets_in_window++;
	EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());

	// We should need number_of_packets_in_window ACK:ed packets before
	// increasing window by one.
	for (int k = 0; k < number_of_packets_in_window; ++k) {
	SendAvailableCongestionWindow();
	AckNPackets(1);
	EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());
	}
	SendAvailableCongestionWindow();
	AckNPackets(1);
	expected_congestion_window += kMaxPacketSize;
	EXPECT_EQ(expected_congestion_window, sender_->CongestionWindow());
	}

	TEST_F(TcpCubicSenderTest, RetransmissionDelay) {
	const int64 kRttMs = 10;
	const int64 kDeviationMs = 3;
	EXPECT_EQ(QuicTime::Delta::Zero(), sender_->RetransmissionDelay());

	sender_->AckAccounting(QuicTime::Delta::FromMilliseconds(kRttMs));

	// Initial value is to set the median deviation to half of the initial
	// rtt, the median in then multiplied by a factor of 4 and finaly the
	// smoothed rtt is added which is the inital rtt.
	QuicTime::Delta expected_delay =
	QuicTime::Delta::FromMilliseconds(kRttMs + kRttMs / 2 * 4);
	EXPECT_EQ(expected_delay, sender_->RetransmissionDelay());

	for (int i = 0; i < 100; ++i) {
	// Run to make sure that we converge.
	sender_->AckAccounting(
	QuicTime::Delta::FromMilliseconds(kRttMs + kDeviationMs));
	sender_->AckAccounting(
	QuicTime::Delta::FromMilliseconds(kRttMs - kDeviationMs));
	}
	expected_delay = QuicTime::Delta::FromMilliseconds(kRttMs + kDeviationMs * 4);

	EXPECT_NEAR(kRttMs, sender_->SmoothedRtt().ToMilliseconds(), 1);
	EXPECT_NEAR(expected_delay.ToMilliseconds(),
	sender_->RetransmissionDelay().ToMilliseconds(),
	1);
	}
	} // namespace test
	} // namespace net