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// Copyright (c) 2015 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 "net/quic/congestion_control/cubic_bytes.h"
#include "base/logging.h"
#include "net/quic/test_tools/mock_clock.h"
#include "testing/gtest/include/gtest/gtest.h"
namespace net {
namespace test {
const float kBeta = 0.7f; // Default Cubic backoff factor.
const uint32_t kNumConnections = 2;
const float kNConnectionBeta = (kNumConnections - 1 + kBeta) / kNumConnections;
const float kNConnectionAlpha = 3 * kNumConnections * kNumConnections *
(1 - kNConnectionBeta) / (1 + kNConnectionBeta);
class CubicBytesTest : public ::testing::Test {
protected:
CubicBytesTest()
: one_ms_(QuicTime::Delta::FromMilliseconds(1)),
hundred_ms_(QuicTime::Delta::FromMilliseconds(100)),
cubic_(&clock_) {}
const QuicTime::Delta one_ms_;
const QuicTime::Delta hundred_ms_;
MockClock clock_;
CubicBytes cubic_;
};
TEST_F(CubicBytesTest, AboveOrigin) {
// Convex growth.
const QuicTime::Delta rtt_min = hundred_ms_;
QuicByteCount current_cwnd = 10 * kDefaultTCPMSS;
QuicByteCount expected_cwnd = current_cwnd + kDefaultTCPMSS;
// Initialize the state.
clock_.AdvanceTime(one_ms_);
EXPECT_EQ(expected_cwnd, cubic_.CongestionWindowAfterAck(
kDefaultTCPMSS, current_cwnd, rtt_min));
current_cwnd = expected_cwnd;
// Normal TCP phase.
for (int i = 0; i < 48; ++i) {
for (QuicPacketCount n = 1;
n < current_cwnd / kDefaultTCPMSS / kNConnectionAlpha; ++n) {
// Call once per ACK.
EXPECT_NEAR(current_cwnd, cubic_.CongestionWindowAfterAck(
kDefaultTCPMSS, current_cwnd, rtt_min),
kDefaultTCPMSS);
}
clock_.AdvanceTime(hundred_ms_);
current_cwnd =
cubic_.CongestionWindowAfterAck(kDefaultTCPMSS, current_cwnd, rtt_min);
EXPECT_NEAR(expected_cwnd, current_cwnd, kDefaultTCPMSS);
expected_cwnd += kDefaultTCPMSS;
}
// Cubic phase.
for (int i = 0; i < 52; ++i) {
for (QuicPacketCount n = 1; n < current_cwnd / kDefaultTCPMSS; ++n) {
// Call once per ACK.
EXPECT_NEAR(current_cwnd, cubic_.CongestionWindowAfterAck(
kDefaultTCPMSS, current_cwnd, rtt_min),
kDefaultTCPMSS);
}
clock_.AdvanceTime(hundred_ms_);
current_cwnd =
cubic_.CongestionWindowAfterAck(kDefaultTCPMSS, current_cwnd, rtt_min);
}
// Total time elapsed so far; add min_rtt (0.1s) here as well.
float elapsed_time_s = 10.0f + 0.1f;
// |expected_cwnd| is initial value of cwnd + K * t^3, where K = 0.4.
expected_cwnd =
11 + (elapsed_time_s * elapsed_time_s * elapsed_time_s * 410) / 1024;
EXPECT_EQ(expected_cwnd, current_cwnd / kDefaultTCPMSS);
}
TEST_F(CubicBytesTest, LossEvents) {
const QuicTime::Delta rtt_min = hundred_ms_;
QuicByteCount current_cwnd = 422 * kDefaultTCPMSS;
QuicPacketCount expected_cwnd = current_cwnd + kDefaultTCPMSS;
// Initialize the state.
clock_.AdvanceTime(one_ms_);
EXPECT_EQ(expected_cwnd, cubic_.CongestionWindowAfterAck(
kDefaultTCPMSS, current_cwnd, rtt_min));
expected_cwnd = static_cast<QuicPacketCount>(current_cwnd * kNConnectionBeta);
EXPECT_EQ(expected_cwnd,
cubic_.CongestionWindowAfterPacketLoss(current_cwnd));
expected_cwnd = static_cast<QuicPacketCount>(current_cwnd * kNConnectionBeta);
EXPECT_EQ(expected_cwnd,
cubic_.CongestionWindowAfterPacketLoss(current_cwnd));
}
TEST_F(CubicBytesTest, BelowOrigin) {
// Concave growth.
const QuicTime::Delta rtt_min = hundred_ms_;
QuicByteCount current_cwnd = 422 * kDefaultTCPMSS;
QuicPacketCount expected_cwnd = current_cwnd + kDefaultTCPMSS;
// Initialize the state.
clock_.AdvanceTime(one_ms_);
EXPECT_EQ(expected_cwnd, cubic_.CongestionWindowAfterAck(
kDefaultTCPMSS, current_cwnd, rtt_min));
expected_cwnd = static_cast<QuicPacketCount>(current_cwnd * kNConnectionBeta);
EXPECT_EQ(expected_cwnd,
cubic_.CongestionWindowAfterPacketLoss(current_cwnd));
current_cwnd = expected_cwnd;
// First update after loss to initialize the epoch.
current_cwnd =
cubic_.CongestionWindowAfterAck(kDefaultTCPMSS, current_cwnd, rtt_min);
// Cubic phase.
for (int i = 0; i < 40; ++i) {
clock_.AdvanceTime(hundred_ms_);
current_cwnd =
cubic_.CongestionWindowAfterAck(kDefaultTCPMSS, current_cwnd, rtt_min);
}
expected_cwnd = 422 * kDefaultTCPMSS;
EXPECT_EQ(expected_cwnd, current_cwnd);
}
} // namespace test
} // namespace net
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