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// Copyright (c) 2014 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 "quic/core/congestion_control/prr_sender.h"
#include <algorithm>
#include "quic/core/crypto/crypto_protocol.h"
#include "quic/core/quic_constants.h"
#include "quic/platform/api/quic_test.h"
namespace quic {
namespace test {
namespace {
// Constant based on TCP defaults.
const QuicByteCount kMaxSegmentSize = kDefaultTCPMSS;
} // namespace
class PrrSenderTest : public QuicTest {};
TEST_F(PrrSenderTest, SingleLossResultsInSendOnEveryOtherAck) {
PrrSender prr;
QuicPacketCount num_packets_in_flight = 50;
QuicByteCount bytes_in_flight = num_packets_in_flight * kMaxSegmentSize;
const QuicPacketCount ssthresh_after_loss = num_packets_in_flight / 2;
const QuicByteCount congestion_window = ssthresh_after_loss * kMaxSegmentSize;
prr.OnPacketLost(bytes_in_flight);
// Ack a packet. PRR allows one packet to leave immediately.
prr.OnPacketAcked(kMaxSegmentSize);
bytes_in_flight -= kMaxSegmentSize;
EXPECT_TRUE(prr.CanSend(congestion_window, bytes_in_flight,
ssthresh_after_loss * kMaxSegmentSize));
// Send retransmission.
prr.OnPacketSent(kMaxSegmentSize);
// PRR shouldn't allow sending any more packets.
EXPECT_FALSE(prr.CanSend(congestion_window, bytes_in_flight,
ssthresh_after_loss * kMaxSegmentSize));
// One packet is lost, and one ack was consumed above. PRR now paces
// transmissions through the remaining 48 acks. PRR will alternatively
// disallow and allow a packet to be sent in response to an ack.
for (uint64_t i = 0; i < ssthresh_after_loss - 1; ++i) {
// Ack a packet. PRR shouldn't allow sending a packet in response.
prr.OnPacketAcked(kMaxSegmentSize);
bytes_in_flight -= kMaxSegmentSize;
EXPECT_FALSE(prr.CanSend(congestion_window, bytes_in_flight,
ssthresh_after_loss * kMaxSegmentSize));
// Ack another packet. PRR should now allow sending a packet in response.
prr.OnPacketAcked(kMaxSegmentSize);
bytes_in_flight -= kMaxSegmentSize;
EXPECT_TRUE(prr.CanSend(congestion_window, bytes_in_flight,
ssthresh_after_loss * kMaxSegmentSize));
// Send a packet in response.
prr.OnPacketSent(kMaxSegmentSize);
bytes_in_flight += kMaxSegmentSize;
}
// Since bytes_in_flight is now equal to congestion_window, PRR now maintains
// packet conservation, allowing one packet to be sent in response to an ack.
EXPECT_EQ(congestion_window, bytes_in_flight);
for (int i = 0; i < 10; ++i) {
// Ack a packet.
prr.OnPacketAcked(kMaxSegmentSize);
bytes_in_flight -= kMaxSegmentSize;
EXPECT_TRUE(prr.CanSend(congestion_window, bytes_in_flight,
ssthresh_after_loss * kMaxSegmentSize));
// Send a packet in response, since PRR allows it.
prr.OnPacketSent(kMaxSegmentSize);
bytes_in_flight += kMaxSegmentSize;
// Since bytes_in_flight is equal to the congestion_window,
// PRR disallows sending.
EXPECT_EQ(congestion_window, bytes_in_flight);
EXPECT_FALSE(prr.CanSend(congestion_window, bytes_in_flight,
ssthresh_after_loss * kMaxSegmentSize));
}
}
TEST_F(PrrSenderTest, BurstLossResultsInSlowStart) {
PrrSender prr;
QuicByteCount bytes_in_flight = 20 * kMaxSegmentSize;
const QuicPacketCount num_packets_lost = 13;
const QuicPacketCount ssthresh_after_loss = 10;
const QuicByteCount congestion_window = ssthresh_after_loss * kMaxSegmentSize;
// Lose 13 packets.
bytes_in_flight -= num_packets_lost * kMaxSegmentSize;
prr.OnPacketLost(bytes_in_flight);
// PRR-SSRB will allow the following 3 acks to send up to 2 packets.
for (int i = 0; i < 3; ++i) {
prr.OnPacketAcked(kMaxSegmentSize);
bytes_in_flight -= kMaxSegmentSize;
// PRR-SSRB should allow two packets to be sent.
for (int j = 0; j < 2; ++j) {
EXPECT_TRUE(prr.CanSend(congestion_window, bytes_in_flight,
ssthresh_after_loss * kMaxSegmentSize));
// Send a packet in response.
prr.OnPacketSent(kMaxSegmentSize);
bytes_in_flight += kMaxSegmentSize;
}
// PRR should allow no more than 2 packets in response to an ack.
EXPECT_FALSE(prr.CanSend(congestion_window, bytes_in_flight,
ssthresh_after_loss * kMaxSegmentSize));
}
// Out of SSRB mode, PRR allows one send in response to each ack.
for (int i = 0; i < 10; ++i) {
prr.OnPacketAcked(kMaxSegmentSize);
bytes_in_flight -= kMaxSegmentSize;
EXPECT_TRUE(prr.CanSend(congestion_window, bytes_in_flight,
ssthresh_after_loss * kMaxSegmentSize));
// Send a packet in response.
prr.OnPacketSent(kMaxSegmentSize);
bytes_in_flight += kMaxSegmentSize;
}
}
} // namespace test
} // namespace quic
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